Category Archives: Physiology

This feature was originally published in issue 386 ofCycling Plus magazine.

Science & Cycling is an annual conference that brings together cyclings finest coaches, exercise physiologists and academics to reveal whats happening at the tip of the peloton, while flagging up what lies ahead down the road.

Its usually held for two days in the week prior to the Tour de Frances Grand Depart, but Covid forced a change this year to Leuven, Belgium, just prior to the World Championships.

And, despite the labyrinth of passenger locator forms, PCR tests and general Covid confusion, we were there to find out how you can ride stronger and more comfortably in 2022

The Canadian team struggled with standing starts at track races. Peter Parks / AFP via Getty Images

Kurt Bergin-Taylor is a former student at Loughborough University, has a PhD in exercise physiology and worked on Cycling Canadas Olympic track programme before taking up his current role as trainer at Team DSM.

Hes a man who successfully marries academia and real-life application, and says all roadies can learn from his time in Canada.

We had a relatively disappointing Worlds in Berlin [2020] and what we noticed especially the women was that we were really struggling over the first two laps, recalls Bergin-Taylor.

Our flying starts were comparable with the best, but our standing starts werent. We didnt have the ability to generate force early on and it was costing us. I wanted to understand why.

Key to uncovering the problem was the uniqueness of a track bike and its fixed gear. With no gears to rapidly shift through from stop to start, that makes torque essentially a measure of force acting on the pedals to make the wheels rotate incredibly important.

Bergin-Taylor played around with gym work, but it wasnt muscle-specific enough.

We needed on-the-bike work for a very short period of time, so we designed a protocol via the Tacx Utility app. On there, you have an isokinetic mode, where no matter how much force is exerted, the speed is fixed, so its useful to train at low revolutions per minute (rpm).

You also have the isotonic mode, which helps you to apply constant force through the pedal stroke.

Working on her standing start helped power Kelsey Mitchell to gold in the sprint at Tokyo 2020. Foto Olimpik / NurPhoto via Getty Images

Twice weekly, the Canadian riders strength training was replaced with three sets of four-second maximal effort work, comprising up to 12 repetitions each time, with two minutes of rest between sets.

It was a disgusting session, but it paid off, as 66 per cent of the participants racked up 3km individual-pursuit personal bests, says Bergin-Taylor.

Kelsey Mitchell, who rode in the velodrome for the first time in 2018, even went on to win sprint gold at the delayed Tokyo Olympics.

Bergin-Taylor concedes its much harder to assess your torque generation through the pedal stroke on the road, but it is possible, though requires much cleaning up of data.

Whats clearer is that we can all benefit from increasing torque, whether thats to accelerate from your mates or laying down the hammer uphill. Adapting Bergin-Taylors session, over-gear work and low-cadence intervals all help here.

You should play around with cadence and gear selection, too, Bergin-Taylor insists.

We know certain sprinters assume they reach maximal power at 120rpm, but if we dial down into the data, we see theyre actually sprinting at 100rpm because they shove the gear down into 54/11 every time.

We then start to educate them and say its fine to shift down to 54/13, as youll hit 120rpm and cycle faster.

Dan Bighams (centre) endless search for speed has taken him to some very interesting places. Jorge Luis Alvarez Pupo / Getty Images

Wattshop was created by Dan Bigham, the new British Hour record-holder. Bigham broke Sir Bradley Wiggins record in October 2021, riding 54.723km in Grenchen, Switzerland, a day after his partner Joss Lowden set a new womens hour record.

Bighams known as a disruptor and was spotted at the recent mixed relay time trial at the Worlds with something stuffed down his jersey.

Cycling commentator Michael Hutchinson referred to it as a gigantic monoboob.

It was revealed soon after to be a radio built into a massive padded pocket to improve aerodynamics. But that wasnt the sole aero advantage Bigham was seeking in Flanders.

We supported Dan at the Worlds, explains Kelly Zwarych, co-founder of slipstreaming pioneers AeroLab Technology, specifically on the course reconnaissance.

Zwarych helped to create the water-resistant data logger that sits beneath aerobar extensions, and provides real-time measurements of all the metrics that time triallists are constantly looking to improve for faster times: aerodynamic drag, coefficient of drag area (CdA), coefficient of rolling resistance (Crr), wind speed, wind yaw angle, wind gusts, plus estimations of drivetrain loss.

In short, it provides a next-generation analysis of aero peformance, taking wind-tunnel feedback into the real world.

AeroLab Technologys logger sits beneath the bars and records a tapestry of data. Gert-Jan D'haene

Its all designed to answer peak-performance questions: which equipments best suited for a given race? What tyres and pressure are best for any given set of wheels? Will a disc wheel really be faster? Why was I slower during the second half of my race but my power was higher?

Let me show you an example from Ironman [triathlon] racing to highlight the importance of aero, says Zwarych.

Two of the best Lionel Sanders and Jan Frodeno roughly use the same equipment, weigh the same and generate a similar power output, so as Lionels shorter, youd expect him to be faster.

But Jans often eight minutes faster over the 180km bike [leg of a triathlon]. Looking at Lionels power output, we can estimate his CdA and, if he reduced that by around 0.019, hed be neck-and-neck with Frodeno and fresh for the run.

This shortfall could be as simple as using the wrong tyres, helmet or hand position.

Currently, this assessments focused on the peak of the performance pyramid, with a six-month lease of the product coming in at nearly $3,000.

There are plans for a more affordable Aero-Lite product to hit the market in spring 2022. This will be under $400 (with UK prices to be confirmed).

In the meantime, simple aerodynamic tweaks every recreational rider can make include wearing close-fitting clothing, zipping up your jersey, spending more time on the drops and shaving your legs.

Using a heart rate monitor can provide insight into whether you are overtraining. Tim de Waele / Getty Images

The wonderfully named Ruby Otter is a lecturer in physiology at the University of Groningen, with a particular interest in the physiological repercussions of stress on endurance performance.

In one study, Otter and her team monitored 150 cyclists, triathletes and runners for two years, asking them to complete a questionnaire, as well as logging their training and using the rate of perceived exertion scale [in Otters, 6 is very light; 20 is maximum exertion] to gauge effort.

We chronicled four areas of stress and recovery: everyday stress, general recovery, sports-specific stress and sports-specific recovery, says Otter.

From this, we could calculate a recovery-stress score. We found that as general stress increased, performance suffered. On the other hand, if an athletes happy with training and life, they see a performance increase.

Another study followed a group of runners whod endured a negative life event, though I cant say what because of ethics.

What Otter did reveal was that the groups running performance dropped by an average 3.6 per cent, plus oxygen consumption cranked up despite running at similar speeds. Somehow, stress had altered their coordination.

Why isnt entirely clear, though a rise in cortisol levels is associated with impaired performance. Whats clearer, says Otter, is that training too intensely when life becomes stressful is a path to overreaching, even overtraining. If your performance is plummeting, and youre irritable and recovering slowly, you could already be there.

But if you want empirical evidence, use the sub-maximal test utilised by Otter: the LSCT Test, created by one of the comperes of this years conference, Rob Lambert.

Its a 17-minute sub-maximal effort on an indoor trainer that requires either a heart rate monitor or power meter.

Cycle for six minutes at 60 per cent of your maximum heart rate (HRmax); six minutes at 80 per cent HRmax; and three minutes at 90 per cent HRmax.

Alternatively, this translates to 50 per cent, 72 per cent and 96 per cent of functional threshold power, or FTP, if you train by watts.

Theres a 30-second buffer between stages, leaving you to finish with 90 seconds where you stop cycling and sit up, so you can monitor your heart-rate recovery (HRR).

Its this final minute thats perhaps the most telling indication of whether youre fit to cycle as, if your heart rate struggles to return to normal levels, its a sign youre potentially on the verge of overtraining.

Over time, youll notice what your average heart rates are over the first three active stages, becoming your own affordable cycling coach.

Its a great way to measure stress and impact training workload accordingly.

With his intermediate and slower twitch fibres, Mathieu van der Poel (second right) is a top road and cyclocross rider. Kristof Ramon / Future Publishing via Getty Images

Your little Bert comes to you and wants to take up cycling. But which discipline? A mountain biker? Or hit the track? Or a roadie? Little Bert asks his parents. He asks his friends. They give him different answers.

Wouldnt it be nice for little Bert if he could know exactly which discipline his muscle type was more suited to? Well, now he can

Those were the words of Eline Lievens, a post-doctoral researcher in exercise physiology and sports nutrition at Ghent University.

Lievens has spent the past few years delving deep into athletes anatomy but, thankfully for said athletes, not via the traditional technique of muscle biopsy.

Though its the gold standard, it requires extracting a muscle fibre from the leg via a long needle and can ascertain an athletes muscle typology; in other words, whether theyre a slow-twitcher or fast-twitcher.

My professor [Pro Wim Derave] has invented a non-invasive technique to measure muscle typology by placing an athlete into a scanner and measuring their carnosine levels, says Lievens.

Carnosine, which is a protein building block, is found to be more readily available in fast-twitch fibres. Vis--vis, high carnosine equals a prevalence of powerful fast-twitch fibres; low carnosine equals a prevalence of less powerful but more stamina-packed slow-twitch fibres.

Why is knowing this split important? As little Bert now understands, talent ID is one reason, albeit there are definite ethical arguments around enforcing your child to choose a sport that matches their genetics rather than what their friends are doing.

It can help at an older age, too, as you might not be riding the discipline that youre genetically best at, adds Lievens. We scanned 80 cyclists from road, track, mountain biking and cyclocross, and showed a correlation between disciplines.

Athletes deemed intermediate or fast typology performed well in BMX and track sprinting. Those with an intermediate and slower typology did well on the road and cyclocross. This partly explains the success of Mathieu van der Poel and Wout van Aert.

Discovering your muscle typology can also help with pacing strategy, says Lievens, as a slow typology might be best suited to even pacing, while a fast typology should start slow and finish fast.

Thats because athletes with a fast typology fatigue quicker, meaning their training volume and frequency should be lower than the slow group, too.

Their recovery duration between intense sessions should also be longer, says Lievens.

As should their recovery duration between intense exercises within training sessions. And their taper longer.

This is all well and good, but this machines currently stationed in Belgium. Back in Britain, you can find a university that offers muscle-biopsy analysis. Or you can go for the more parochial, albeit non-invasive and pretty accurate methods of physical tests.

These include a 60-second jump test, where you jump continuously for 60 seconds and see how your vertical distance tails off. A dramatic height and then drop-off suggests youre a fast-twitcher; slow-twitchers are more of a plateau.

Victor Scholler (right) works with Groupama-FDJ. Sebastien Bozon / AFP via Getty Images

Victor Scholler holds a PhD in sport science and currently works with the French WorldTour team Groupama-FDJ. He also knows how to make a cyclist comfortable on the bike.

Through our research, its clear that a dynamic bike fit is better than a static alternative, says Scholler.

A dynamic bike fit is like those delivered by Retl. In general, theyll involve a comprehensive physiotherapy assessment off the bike before analysing your riding technique on a jig via motion-capture technology. The data is then analysed by the practitioner. But, says Scholler, not all professional bike fits are equal.

3D motion capture is superior to the 2D system, as its a more realistic interpretation of your pedal stroke. But arguably even more important than that is the quality of the person undertaking your bike fitting.

Training and communication are key, so that you leave your fit sessions with things to work on when implementing any changes. Choose wisely, however, and its worth the outlay.

Dynamic assessment is better than static because it takes into account your actual pedal stroke. Riders vary greatly in how much they flex their ankles.

This alters your knee angle, which is the main focus when it comes to saddle height because you want your quadriceps to function at their optimal length to deliver power.

Victor Schollers research has shown that dynamic bike fits are superior to static ones. Andy Saunders / Immediate Media

A dynamic fit takes into account factors like hip rocking, too, plus leg differences.

Scholler supports his advice with research, suggesting knee injuries in the professional ranks are down from 28 per cent to 6 per cent, most likely due to the improvements in bike fitting.

That said, Scholler suggests static fitting still has a place. For a lot of people, especially if youre new to cycling, its probably good enough.

How you calculate yours is simply measuring your in-seam. Your saddle height should be around 106 to 109 per cent of this figure.

To do this, stand barefoot against a wall with a thick book between your legs. Pull the book upwards so it feels almost uncomfortable.

Spin around and mark the top of the book on the wall. This is your in-seam. Now measure this distance to the floor, multiply by 1.06 and you have your saddle height, which you can play around with when out riding. Its an old-school solution that still has its place in the modern world.

If youre interested in other techniques for determining the correct saddle height for you, check out our full in-depth guide.

This was the seventh edition of the Science & Cycling Conference, which was first held prior to the 2014 Tour de France in Leeds, Yorkshire.

Its a meeting place for experts in the field of cycling to share their latest research and for companies to give demonstrations of their products. Dates for the 2022 edition have yet to be confirmed.

Originally posted here:
5 frontiers of cycling science that could make you faster in 2022 - BikeRadar

Physiology

UF researchers receive federal funding to fight citrus greening – Wink News

December 2, 2021 medical

IMMOKALEE

University of Florida researchers have received federal funding to combat citrus greening. This disease is devastating to citrus growers. Now, WINK News is showing you the research that is already underway to fight this disease.

Just as people are dealing with the pandemic, the citrus industry is dealing with a pandemic of its own citrus greening. Ron Mahan is the CFO and vice president of Tamiami Citrus. As a state, the industry was producing 200 to 240 million boxes, 90-pound boxes a year of oranges, most of that going into juice, although some sold fresh as well, but today, were now producing at less than 50 million boxes, said Mahan.

Thanks to more than $2 million from the U.S. Department of Agriculture, UF researchers are working to combat citrus greening. Ute Albrecht and Ozgur Batuman gave WINK News a glimpse into how the money will help them.

Ute Albrecht is an Assistant Professor of plant physiology. By just simply spraying the tree with a new therapy, it doesnt get into the plant. Albrecht went on to say, the method that I will be involved in is through trunk injection.

Like how humans get shots at doctors offices, one of Albrechts projects involves exploring different chemical compounds to inject in citrus trunks to fight greening.

Batuman works with a team to graft greening-resistant Australian finger limes to sweet orange trees to boost resilience. Think of it like an organ transplant or a blood transfusion, but for plants.

As if you are taking my arm and attaching to you, and you are taking some of the useful genes from me to yourself. Very straightforward and can be done instantly, Batuman said.

Growers are putting the pieces together and keeping citrus on the table.

Researchers in Immokalee also use mesh covers to protect trees from the specific insect responsible for transmitting citrus greening bacteria.

Follow this link:
UF researchers receive federal funding to fight citrus greening - Wink News

Physiology

Doing This One Thing While Running Burns Twice the Calories, Science Says Eat This Not That – Eat This, Not That

December 2, 2021 medical

Losing weight is supposedly simple. Just burn more calories than you eat, right? That may seem like an easy recipe, but millions will attest that shedding extra pounds is often easier imagined than accomplished.

The fact remains that exercising is still a key aspect of losing weight and toning up. Consider this research published in the scientific journal Medicine & Science in Sports & Exercise: Scientists found that a mere hour of aerobic exercise is all it takes to jumpstart accelerated energy and calorie-burning on the cellular level. Put another way, exercise burns more calories and conditions the entire human body to burn energy more efficiently. So, while a single jog or run may not instantly lead to six-pack abs, each bout of exercise is absolutely making a difference.

"It's pretty remarkable that even after just one hour of exercise, these people were able to burn off a little more fuel," says lead study author Matt Robinson, an assistant professor in the College of Public Health and Human Sciences at Oregon State University. "From a big picture health perspective, it's very encouraging for people to realize that you can get health benefits from a single session of exercise. We're trying to encourage people, 'You did one, why don't you try to do two? Let's do three.'"

Still, if you can't help but think there must be a way to burn a bit more calories on average while getting in some cardio, we have some good news! Doing this one thing while running can help double the amount of calories burned. Keep reading to learn more, and next, don't miss This Workout Is Three Times Better for Your Health Than Walking, New Study Says.

Consistency is usually a positive across most areas of life, but plenty of relevant scientific research tells us that varying up cardio exercises with interval training is a great way to burn more calories. Often referred to as HIIT (high-intensity interval training), this approach to cardio is all about combining intense, short bursts of motion with longer periods of rest or "cooling down."

It may sound counterproductive to slow down while out for a run, but engaging in interval training activates both the aerobic and anaerobic systems within the body, creating an oxygen shortage that promotes greater and more prolonged calorie expenditure. "There's nothing wrong with steady-state cardio, but I would suggest adding sprint intervals to your cardio workout to bump up the burn," Gunnar Peterson, celebrity PT, told NBC News.

Still skeptical? Take a look at this study published in The Journal of Strength and Conditioning Research. The research team measured and compared calories burned during a 30-minute bout of HIIT, regular cardio, and weightlifting. Sure enough, the HIIT cohort ended up burning 25-30% more calories than the other groups.

Another study released in the Journal of Applied Physiology concludes that interval training increases the amount of fat burned during an hour of exercise by as much as 36%. Not to mention a 13% overall increase in cardiovascular fitness. Over the course of 10 sets, participants engaged in cardio at 90% effort for four minutes at a time, followed by two minutes of rest.

Related: This Workout Plan Will Keep You Lean Throughout the Holidays.

HIIT also minimizes the time we spend exercising while maximizing the health benefits. HIIT workouts can be finished in as little as 15 minutes, but often burn more calories than traditional cardio routines lasting twice as long if not even longer.

One study released in The Journal of Applied Physiology even reports that just a few 30-second intense sprints improve overall fitness just as much as a full hour of jogging!

Circling back to the first study mentioned above, keep in mind that participants assigned to the HIIT group not only burned significantly more calories than the others but also accomplished this while exercising for a fraction of the time. While everyone else had to work out for 30 minutes straight, the HIIT exercisers only moved at maximum intensity for 20 seconds at a time, followed by 40 seconds of cooling down.

Related:Sign up for our newsletterfor the latest health and fitness news!

HIIT can even help you burn more calories while you're lounging on the couch. Calories burned while at rest are referred to as EPOC, or post-exercise energy consumption. Well, according to the American Council on Exercise, HIIT is the single best way to jumpstart EPOC!

Similarly, this research tells us that just a couple of minutes of intense training (spread out across 25 minutes of interval training) promotes increased calorie-burning for the entire rest of the day. Subjects in this study burned as much as 200 extra calories during workout days despite only exercising vigorously for about two and a half minutes total. With these extended calorie-burning benefits in mind, burning double the calories via HIIT doesn't sound so far-fetched after all.

Related:Secret Effects of Lifting Weights Just Once Per Week, Science Says

If you're still on the lookout for more ways to reap further fitness rewards from running, consider going out for your daily jog first thing in the morning before sitting down for some breakfast.

This study published in The British Journal of Nutrition found that going for a morning run on an empty stomach results in nearly 20% more fat burned! More research published in The Journal of Clinical Endocrinology and Metabolism came to similar conclusions, reporting that a pre-breakfast workout burns twice as much fat.

For more, check outThis 5-Move At-Home Workout Will Help You Build Strength.

Physiology

Molecular mechanisms of sperm motility are conserved in an early-branching metazoan – pnas.org

December 2, 2021 medical

Significance

Reef-building corals are the keystone species of the worlds most biodiverse yet threatened marine ecosystems. Coral reproduction, critical for reef resilience, requires that coral sperm swim through the water column to reach the egg. However, little is known about the mechanisms that regulate coral sperm motility. We found here that coral sperm motility is pH dependent and that activation of motility requires signaling via the pH-sensing enzyme soluble adenylyl cyclase. This study reveals the deep conservation of a sperm activation pathway from humans to corals, presenting the first comprehensive examination of the molecular mechanisms regulating sperm motility in an early-diverging animal. These results are critical for understanding the resilience of this sensitive life stage to a changing marine environment.

Efficient and targeted sperm motility is essential for animal reproductive success. Sperm from mammals and echinoderms utilize a highly conserved signaling mechanism in which sperm motility is stimulated by pH-dependent activation of the cAMP-producing enzyme soluble adenylyl cyclase (sAC). However, the presence of this pathway in early-branching metazoans has remained unexplored. Here, we found that elevating cytoplasmic pH induced a rapid burst of cAMP signaling and triggered the onset of motility in sperm from the reef-building coral Montipora capitata in a sAC-dependent manner. Expression of sAC in the mitochondrial-rich midpiece and flagellum of coral sperm support a dual role for this molecular pH sensor in regulating mitochondrial respiration and flagellar beating and thus motility. In addition, we found that additional members of the homologous signaling pathway described in echinoderms, both upstream and downstream of sAC, are expressed in coral sperm. These include the Na+/H+ exchanger SLC9C1, protein kinase A, and the CatSper Ca2+ channel conserved even in mammalian sperm. Indeed, the onset of motility corresponded with increased protein kinase A activity. Our discovery of this pathway in an early-branching metazoan species highlights the ancient origin of the pH-sAC-cAMP signaling node in sperm physiology and suggests that it may be present in many other marine invertebrate taxa for which sperm motility mechanisms remain unexplored. These results emphasize the need to better understand the role of pH-dependent signaling in the reproductive success of marine animals, particularly as climate change stressors continue to alter the physiology of corals and other marine invertebrates.

The activation of sperm motility requires precise temporal and spatial control in order to maximize chances of eggsperm contact and fertilization (1). Despite the vital importance of this process for reproductive success across metazoan phyla, the molecular mechanisms that regulate sperm activation remain poorly understood. Sperm are typically held in an inactive state within the male prior to release into either the surrounding water column during broadcast spawning, as in early-branching metazoans and many bilaterians, or directly into the female oviduct during copulation, as in some bilaterians (2). The signals that trigger sperm motility following release vary between environments and species and can include changes in osmolarity, ion concentrations (e.g., bicarbonate), and/or chemical signals released by eggs (3). Even with the considerable differences in reproductive ecology and activation cues that characterize different taxa, the downstream signaling pathways that activate motility are highly conserved across the few taxa that have been described to date, namely mammals (phylum Chordata) and sea urchins (phylum Echinodermata). Because of the historical focus on these two phyla, which are closely related in the context of metazoan evolution, we know very little about the broader evolution of the molecular pathways that activate sperm motility across the metazoan phylogeny and especially in earlier branching metazoan phyla. This has left a significant gap in our understanding of the evolution of the mechanisms that regulate sperm function, an important issue to address given the importance of these mechanisms for determining animal fitness in a changing environment.

Reef-building corals, members of the early-branching phylum Cnidaria, are an evolutionarily and ecologically important model system for understanding mechanisms of sperm motility. First, corals belong to one of the earliest phyla to evolve organized tissues, and as diploblasts, they lack the mesoderm present in bilaterians (4). Second, corals are the foundational species of coral reefs, one of the most biodiverse ecosystems on the planet (5). Coral reproduction is essential for the persistence of reefs worldwide (6) and in most species involves the tightly coordinated release of sperm and eggs into the water column on just a few nights each year (7, 8). This process is currently threatened by a combination of local stressors (9) and global climate change (1012). Sperm in particular are acutely susceptible to environmental disturbances due to their small size and brief lifespan (13), and climate change stressors including ocean warming and acidification have reduced coral sperm production (11, 14), motility (10, 15, 16), and fertilization success (17, 18) in several species. The mechanisms driving these declines in sperm performance are unknown, but both warming and acidification may disrupt coral cellular metabolism and acidify the cytosol (1921), two processes that are important for sperm motility in other species (22). Indeed, initial evidence indicates that alkalinization of coral sperm cytosol promotes motility (23), highlighting the importance of understanding the molecular pathways that connect pH-dependent signaling with changes in cellular performance.

Alkalinization of the sperm cytosol acts as a critical intracellular messenger controlling the onset of motility in several species (3, 24, 25). In sea urchins, the binding of egg-derived peptides [e.g., speract (2)] to guanylyl cyclase (GC) receptors at the cell surface activates a sperm-specific Na+/H+ exchanger [SLC9C1 (26)], which increases cytoplasmic pH through its proton efflux activity. In both spawning marine invertebrates and mammals, this alkalinization stimulates cAMP production via the enzyme soluble adenylyl cyclase [sAC (27)], leading to protein kinase A (PKA)-dependent phosphorylation of flagellar proteins and calcium signaling via CatSper channels (2), which together stimulate flagellar beating. Cnidarian GC-A receptors and CatSper channels are highly conserved with those from sea urchins (28, 29), and although the other constituents of the pathway have yet to be investigated, these reports suggest that this molecular mechanism may be conserved in early-branching metazoans. Mammals have evolved a distinct activation signal that nonetheless utilizes a similar signaling cascade to that of sea urchins, whereby elevated levels of bicarbonate in the female reproductive tract activate sAC (30), and the resulting burst of cAMP activates PKA, leading to phosphorylation of flagellar proteins and ultimately motility. Each component of this conserved pathway appears to be necessary for sperm motility and fertilization in mammals, as mice lacking SLC9C1, sAC, PKA, or CatSper display severe sperm motility defects, rendering them infertile (3135). These studies support the conservation of sAC-cAMP as a central signaling node in sperm activation across bilateria; however, there is no data currently on the role of sAC-cAMP signaling in early-branching metazoans. In corals, somatic tissues express a functional homolog of sAC that is stimulated by bicarbonate to make cAMP (36), and this enzyme plays a role in responding to pH fluctuations within the cell (37), leaving open the promising possibility that this pathway is functionally conserved in coral sperm.

In order to test the hypothesis that sperm motility in early-branching metazoans is regulated by a molecular signaling pathway that is conserved with bilaterians, we examined the role of intracellular pH, sAC, cAMP, and PKA signaling in sperm motility in the reef-building coral Montipora capitata using a combination of microscopy, biochemistry, and immunological assays. In addition, we analyzed the expression and conservation of key proteins in the echinoderm motility initiation pathway in M. capitata sperm via interrogation of RNA sequencing (RNA-seq) databases and in silico structural analyses. This comprehensive examination of the intracellular signaling pathways that regulate sperm motility in an early-branching metazoan highlights the functional conservation of a fundamental pathway essential for animal reproduction. Furthermore, the mechanisms underlying coral sperm motility have important implications for determining how climate change will influence the reproductive success of corals and other marine animals.

To induce cytosolic alkalinization, sperm from the coral Montipora capitata were suspended in sodium-free seawater (NaFSW) and exposed to 20 mM NH4Cl (23, 38, 39). Intracellular pH (pHi) and motility were then monitored simultaneously by confocal microscopy using the fluorescent dye SNARF-1-AM (SI Appendix, Fig. S1). Prior to NH4Cl treatment, sperm were inactive (0% motility) and had a mean pHi of 7.52 0.05 (Fig. 1A). Sperm pHi increased following NH4Cl exposure, reaching a peak of 8.31 0.04 within 45 s (Fig. 1A), equivalent to over an 80% decrease in H+ concentration. Sperm pHi remained above pH 8.0 for at least 2:30 min and then started to decline after 3:00 min, reaching initial levels after 4:30 min and continuing to decline over the next 2:00 min, reaching a minimum of pH 7.26 0.02 (Fig. 1A). Motility increased instantaneously following exposure to NH4Cl (visual observation), reaching 100% within 45 s postexposure (Fig. 1A). Motility remained near 100% for 3:20 min and then rapidly decreased to 7.1% after 4:25 min and remained near zero until the end of the experiment (Fig. 1A). This drop in motility was concurrent with declining pHi, with a possible motility threshold of pHi 7.8. Treatment of sperm with 20 mM NH4Cl also led to a rapid increase in cAMP content within 15 s followed by a decline by 60 s postexposure (Fig. 1B). Interestingly, the absolute concentration of cAMP produced by sperm varied between spawning seasons, with a peak of 1.7 0.017 nmol mg1 occurring in 2019 (Fig. 1B) and peaks between 45 to 96 pmol mg1 in 2021 (SI Appendix, Fig. S2). Sperm cAMP concentrations remained two- to threefold higher than initial levels for up to 5 min postexposure, while unexcited control sperm exhibited little change in cAMP content (Fig. 1B and SI Appendix, Fig. S2).

Response of sperm from the coral Montipora capitata to ammonium chloride (NH4Cl) treatment and sAC inhibition. (A) Coral sperm motility (solid line) and pHi (dashed line) after exposure of sperm in NaFSW to 20 mM NH4Cl (n 15 cells per time point). Gray shaded region indicates 99% CI of sperm initial pHi prior to activation (7.52 0.05). (B) Concentration of cAMP in coral sperm in NaFSW following treatment with 20 mM NH4Cl (black squares) or control (open squares). cAMP levels are normalized to total protein. (C) Circular motility of coral sperm in NaFSW preincubated with 0.2% DMSO (black) or 50 M sAC inhibitor KH7 (gray) before and after treatment with NH4Cl. The horizontal black bar represents the mean of n 3 replicates. (D) The median speed of coral sperm in seawater pretreated with 0.2% DMSO or 50 M KH7. The horizontal black bar represents the mean of n = 5 replicates. Error bars in A, C, and D indicate SEM; error bars in B indicate SD; where not visible, they fall within the symbol. Significance is denoted as n.s. (no significance), *P 0.05, **P 0.01.

In order to determine if sAC was necessary for NH4Cl-stimulated sperm motility, sperm were incubated with the sAC-specific inhibitor KH7 or a dimethyl sulfoxide (DMSO) carrier control prior to NH4Cl treatment. In the DMSO pretreatment, addition of NH4Cl led to a significant increase in the percentage of cells exhibiting circular motility, from 8.9 17.6% prestimulation (Video S1) to 50.3 28.9% poststimulation (P = 0.0423, Tukey's posthoc test; Video S2 and Fig. 1C). In contrast, pretreatment with 50 M KH7 abolished the activation of circular motility following NH4Cl treatment, which remained <1% (Fig. 1C and Video S3). The flagella of KH7-treated cells remained structurally intact, displaying a weak beating motion near the head that did not propagate along the length of the flagellum (Video S4). KH7 treatment also caused a significant decrease in the median speed of coral sperm maintained in seawater, from 7.0 1.3 to 4.1 0.6 m s1 (P = 0.0079, Wilcoxon test; Fig. 1D).

The sequence of M. capitata sAC (mcsAC) was identified by querying an M. capitata sperm genome (40) using a complementary DNA (cDNA) sequence from the coral Pocillopora damicornis [pdsAC (37)]. The predicted protein was 75.7% similar to pdsAC and 48.3% similar to sAC from the sea urchin Strongylocentrotus purpuratus (spsAC; SI Appendix, Table S1). Sequence alignment with metazoan homologs (SI Appendix, Table S2) revealed that mcsAC contained both conserved cyclase homology domains (CHD1 & CHD2; SI Appendix, Fig. S3) necessary for bicarbonate-stimulated cAMP production (41). Within its catalytic core, mcsAC shared six of seven active site residues with M. musculus sAC (42) and seven of seven with cnidarian (pdsAC) and echinoderm sAC (spsAC; SI Appendix, Fig. S3). mcsAC activity was detected in crude M. capitata sperm lysates as evidenced by a dose-dependent activation of AC activity in response to 05 mM Mn2+ (SI Appendix, Fig. S4), a cofactor that activates sAC but not related transmembrane ACs [tmACs (43)]. Like pdsAC, mcsAC lacked the short autoinhibitory peptide directly C-terminal to CHD2 (SI Appendix, Fig. S3) that has been described in mammals (44). mcsAC also contained a long (140 kDa) C-tail of unknown function, which has been found in all metazoan sAC genes.

Expression of mcsAC in sperm was confirmed by Western blot using anti-coral sAC antibodies recognizing CHD2. The predominant isoform was the full-length protein (195 kDa, sACFL; Fig. 2A) followed by an 110-kDa isoform (sAC110; Fig. 2A) and two additional isoforms of 55 and 45 kDa (sAC55 and sAC45, respectively) which were detected at low levels (Fig. 2 A, Right). sAC55 and sAC45 are similar in size to two truncated forms of sAC identified in mammalian somatic tissues, including a highly active form composed of only CHD1 and 2 [sACT; 55 kD (41)] and possibly an atypical variant of sAC lacking CHD1 [46 kDa (45)]. Expression of sACFL was not detected in adult M. capitata tissues, which only expressed the smallest 45-kDa isoform at detectable levels (Fig. 2B). Running as a doublet, these bands may represent posttranslational modifications of sACT.

Expression of sAC in Montipora capitata sperm. (A) Western blot of the sAC protein in sperm from three different individuals (lanes 1 to 3) shows high expression of two isoforms (sACFL, sAC110) and low expression of two isoforms (sAC55, sAC45). (Inset) High exposure of same blot. Approximate size (kDa) of each protein is indicated on the left. (B) Western blot of somatic tissues from four M. capitata adults (lanes A to D) show expression of a single sAC isoform (sAC45). (C) Diagram of the architecture of coral sperm, identified by ref. 46. The head houses the nuclei and the surrounding acrosome compartment. The flagellum contains the axoneme formed from a 9 + 2 microtubule bundle and, immediately posterior to the head, a mitochondria-rich midpiece. (D) Brightfield image of sperm. (E) Corresponding fluorescence micrograph showing localization of sAC (green), DNA (blue), and flagella (magenta; stained with anti--tubulin antibodies). (F) Corresponding image of coral sAC expression alone. (G) Brightfield image of a sperm cell with the flagellum extended. (H) Corresponding fluorescence micrograph highlighting coral sAC expression along the length of the flagellum. Arrowheads indicate the midpiece of the flagellum containing the mitochondrial sheath, and asterisks indicate the flagellum.

The subcellular localization of mcsAC in sperm was determined by immunocytochemistry using the same anti-coral sAC antibodies. M. capitata sperm consist of a head that contains the nucleus and acrosomal compartment and a flagellum with a single 9 + 2 microtubule bundle that includes two distinct regions: the midpiece adjacent to the head that contains five to six mitochondria followed by the principle piece (i.e., tail) containing just the axonemal fibers (Fig. 2C) (46). M. capitata sperm expressed mcsAC throughout the entire cell, and expression was most concentrated in the midpiece (Fig. 2 DF). mcsAC was also present in low abundance at the tip of the sperm head in the predicted acrosomal region (Fig. 2 DF) and across the entire length of the flagellum (Fig. 2 G and H), where it colocalized with -tubulin, the primary component of the axonemal fibers (Fig. 2 E and F). Controls confirmed antibody staining was specific for mcsAC for both Westerns (SI Appendix, Fig. S5 B and D) and immunostaining (SI Appendix, Fig. S6).

Next, we next analyzed the expression of key players in the sAC-dependent sperm activation pathway in coral sperm, both those conserved across bilateria (PKA, SLC9C1 [sNHE], and CatSper) and those that have only been described in sea urchins (GC-A, HCN, and CNGK; Fig. 3A). We began by searching for each protein sequence in two M. capitata genomes (40, 47) using sea urchin homologs to identify reciprocal best BLAST hits (SI Appendix, Table S1). M. capitata genomic sequences were then used to query a sperm RNA-seq database derived from the same species (48). Further structural analysis was carried out using sequence alignment and transmembrane helix prediction software in order to identify key functional domains (Fig. 3 BH and SI Appendix, Tables S2S4 and Figs. S7S10). In cases in which the M. capitata genome predicted a structurally incomplete protein, a comparison with the well-annotated genome of P. damicornis was used to identify potential missing sequences (dotted lines; Fig. 3 D, F, and G). Together, these analyses identified a single homolog of each gene in the M. capitata genome and at least nine transcripts of 95% or greater homology to the genomic sequence expressed in the M. capitata sperm transcriptome (SI Appendix, Table S1).

A pH-dependent motility pathway is conserved in sperm from the coral Montipora capitata. (A) Diagram of the pH-sAC-cAMP motility pathway from echinoderms. Egg-derived chemoattractants bind to a guanylyl cyclase receptor (GC-A) which produces cGMP to stimulate CNGK-mediated K+ efflux and membrane hyperpolarization (Hyp). CNGK activates the H+/Na+ exchanger SLC9C1, which raises cytoplasmic pH, thereby activating sAC-dependent cAMP production and driving PKA-dependent phosphorylation of axonemal proteins controlling motility. sAC-dependent cAMP feeds back to maintain SLC9C1 activity and promotes hyperpolarization-dependent activation of HCN, which depolarizes (Dep) the cell via Na+ influx. The CatSper channel responds to both depolarization and elevated pH to generate Ca2+ influx signals that alter the flagellar waveform. (B) Expression of a predicted 40-kDa M. capitata PKA C catalytic subunit was confirmed by Western blot. The protein ran as a triplet, likely because of activating phosphorylations. (C) Western blot analysis also detected an increase in PKA substrate phosphorylation in sperm stimulated with 20 mM NH4Cl. Predicted domain structures of M. capitata homologs of (D) mcSLC9C1, (E) mcCatSpercomp, (F) mcGC-A, (G) mcCNGK, and (H) mcHCN. Conserved protein domains and amino acid signatures: K, kinase domain; S, transmembrane segment; NHE, sodium hydrogen exchange domain; *, includes NHE consensus sequence; VSD, voltage sensing domain; +, positively charged amino acids involved in voltage sensing; CNBD, cyclic nucleotide-binding domain; P, pore-forming domain; SF, selectivity filter; CC, coiled-coil domain; GC, guanylyl cyclase domain; KL, kinase-like domain; LB, ligand-binding domain.

The catalytic domain of PKA in M. capitata sperm was 90.6% similar to S. purpuratus PKA C, encoding a polypeptide of 40 kDa (Fig. 3B and SI Appendix, Table S1). Protein expression of PKA C in M. capitata sperm was further confirmed by Western blot (Fig. 3B). The band ran as a triplet, likely because of activating phosphorylation of the kinase activation loop (49). PKA substrate phosphorylation in sperm activated with 20 mM NH4Cl was also detected by Western using an antibody that recognized the consensus sequence of the enzyme (RRXS*/T*; Fig. 3C). Many proteins ranging in size from 15 to 250 kDa exhibited a pattern of increased phosphorylation upon motility stimulation.

The M. capitata homolog of SLC9C1 (i.e., sNHE), a sodium/hydrogen exchanger that elevates cytoplasmic pH upstream of sAC and PKA (Fig. 3A), was 69.8% similar to SLC9C1 from S. purpuratus (SI Appendix, Table S1). mcSLC9C1 contained an N-terminal sodiumproton exchanger (NHE) domain with the canonical cation-binding motif of 1:1 electroneutral exchangers embedded within the predicted S3-4 region, identical to echinoderms but distinct from mammals (Fig. 3D and SI Appendix, Fig. S7A). C-terminal to the NHE, mcSLC9C1 also had both a voltage-sensing domain (VSD) and a cyclic nucleotide-binding domain (CNBD; Fig. 3D). The mcSLC9C1 VSD displayed the four-transmembrane (S1-4) architecture, including the seven positively charged residues in S4 found in the Drosophila Shaker channel (SI Appendix, Fig. S7B) (50). While these charged residues are entirely conserved in echinoderms, they are only semiconserved in mammals, reflecting the divergence of the pathway from its invertebrate ancestors.

The four polypeptides that assemble to form the pore of the CatSper calcium ion channel [CatSper1-4 (51)] were identified in M. capitata sperm and shared up to 70.7% similarity with their S. purpuratus homologs but were 27.7 to 74.3% shorter, likely due to incomplete genome coverage (SI Appendix, Table S1 and Fig. S8A). When the partial sequences were overlaid, a consensus of the classic 6TM-type architecture common to CatSpers emerged (Fig. 3E). For example, mcCatSper2-4 each contained a VSD with four to five charged amino acids in transmembrane segment S4 as compared with the six to seven found in the sea urchin S. purpuratus and the two to four found in M. musculus (SI Appendix, Fig. S8B). In mcCatSper1, 2, and 4, segments S5 and S6 were linked by a short interconnecting helix, or selectivity filter, with the canonical [T/S]x[D/E]xW motif of Ca2+-selective channels (Fig. 3E and SI Appendix, Fig. S8C). mcCatSpers 2 and 3 contained short, cytoplasmic domains C-terminal to S6 that were predicted to form coiled-coil domains, important for subunit oligomerization in mammals (SI Appendix, Table S4 and Fig. S8A) (51, 52). Transcripts of CatSper2-4 were identified in M. capitata sperm (SI Appendix, Table S1), and while mcCatSper1 was not found, it is notable that the stable expression of the four bilaterian subunits is highly interdependent (53). Thus, the absence of mcCatSper1 is likely due to an inability to identify the C terminus of the protein via homology searches of the genome, which, combined with the inherent 3' bias of the poly-A selection method used to generate the RNA-seq library (48), likely obscured actual expression data.

Considering specific members of the sea urchin pathway (Fig. 3A), the M. capitata guanylyl cyclase receptor (mcGC-A) gene was 42.3% similar to S. purpuratus GC-A (synonymous with the Speract receptor) and 78.0% similar to that of the coral Euphyllia ancora (eaGC-A; SI Appendix, Table S1). mcGC-A contained an intracellular kinase-like homology (KL) domain and a guanylyl cyclase catalytic domain (CY) as well as an extracellular ligand-binding domain (LB; Fig. 3F), similar to both the Speract receptor and eaGC-A. Sea urchin sperm activation via GC-A also involves the ion channels CNGK and HCN. CNGK-dependent membrane hyperpolarization activates SLC9C1 to induce cytosolic alkalinization, whereas HCN-dependent membrane depolarization occurs downstream of sAC to facilitate CatSper activation (Fig. 3A) (2). Like CatSper, both CNGK and HCN assemble as a tetramer of 6TM-type subunits, however, with a C-terminal CNBD replacing the CatSper coiled-coil domain (Fig. 3 G and H, respectively). mcCNGK was 53.9% similar to CNGK characterized in the sea urchin Arabica punctulata (SI Appendix, Table S1), and its four subunits were encoded as domains within a single polypeptide (Fig. 3G). In contrast, HCN channels form from a homotetramer (54), and the single 6TM repeat of mcHCN (Fig. 3H) was 73.1% similar to the S. purpuratus homolog (spHCN;SI Appendix, Table S1). Like their echinoderm homologs, the selectivity filters of both mcCNGK and mcHCN contained a canonical cation-binding GYG motif of cation channels (SI Appendix, Figs. S9 and S10A). This region in mcHCN was nearly identical to spHCN (100% similarity; SI Appendix, Fig. S10A), a channel whose weak selectivity for K+ [PK/PNa = 4.7 (55)] causes a depolarizing inward Na+ current under physiological conditions (56). In contrast, the T/S-rich region in the mcCNGK filter (SI Appendix, Fig. S9) is indicative of highly K+-selective channels (56). Additionally, mcHCN transmembrane segment S4 contained eight positively charged amino acids, broken into two clusters of three to four residues, that comprise a predicted VSD (SI Appendix, Fig. S10B). mcCNGK, however, lacked a VSD, suggesting this channel responds solely to cGMP and not to changes in membrane polarization.

Here, we demonstrate in an early-branching metazoan that sperm motility is initiated via a pH- and cAMP-dependent signaling pathway. Chemical alkalinization of inactive Montipora capitata sperm was sufficient to induce 100% motility. A subsequent reacidification of the cytosol began 2.5 min after alkalinization, with pHi eventually passing below the initial setpoint. This overcompensation is consistent with the presence of active acidbase compensatory mechanisms in coral sperm. In addition, once pHi declined below pH 7.8, sperm motility also began to decline, indicating that coral sperm may have a threshold for motility around pHi 7.8, similar to echinoderm sperm (24). While the mechanistic link between declining pHi and reduced coral sperm motility remains uncharacterized, data from other marine invertebrate models suggest that the dynein ATPase, the key motor protein driving flagellar beating, is most active when pHi is 7.5 and may be directly inhibited by reacidification (22, 57). Cytosolic alkalinization in coral sperm also coincided with rapid cAMP production that peaked within the first 30 s of activation, indicating that this universal second messenger molecule is involved in the onset of coral sperm motility. A similar burst of total cAMP occurs in both mammalian (58) and echinoderm sperm (59) and in those taxa initiates a signaling cascade that up-regulates flagellar beating and alters the flagellar waveform (2). Our data suggest that this pH-dependent cAMP signaling is not unique to bilaterian sperm but instead arose before the split of the cnidarian and bilaterian lineages.

The molecular pH sensor sAC is the primary source of cAMP driving the onset of sperm motility in bilaterians and it plays a central role in the regulation of sperm physiology (30, 60). We found here that sAC is expressed and active in coral sperm and is required for the onset of coral sperm motility in response to pH. Thus, our data extend the conservation of the sAC signaling node in sperm prior to divergence with bilaterians. While the role of tmAC in coral sperm cAMP production cannot be ruled out, these enzymes are insensitive to pH and bicarbonate and do not play a major role in flagellar motility in bilaterian sperm (27, 61, 62). In contrast, sAC is activated in response to local fluctuations in sperm cytoplasmic pH in both mammals (63) and echinoderms (64), and our data confirm that sAC in corals is both active in sperm and an important regulator of motility.

Coral sperm expressed sAC throughout the head, midpiece, and distal region of the flagellum, indicating that sAC may be involved in multiple aspects of coral sperm physiology. For example, abundant expression along the midpiece, a localization that is conserved in sea urchin (64) and mammalian sperm (30), suggests that coral sAC may influence cellular respiration. Sperm motility and respiration are tightly coupled through the dynein ATPase, which consumes the vast majority of cellular ATP (22). Studies of bilaterian somatic cells have uncovered a unique pool of sAC that resides within the mitochondrial matrix and promotes PKA-dependent up-regulation of oxidative phosphorylation (65). Here, we show that the onset of coral sperm motility coincides with an increase in PKA substrate phosphorylation throughout the cell. While the identity of coral PKA substrates remain unknown, many of the PKA targets in sea urchin sperm are mitochondrial proteins (66). It is possible that regulation of mitochondrial output via sAC-PKA signaling in invertebrate sperm is an additional means of tuning flagellar motility. Importantly, because mitochondrial function and sperm motility are both impaired under simulated ocean acidification in sea urchin, mussel, and ascidian sperm (21, 67), a description of the molecular mechanisms underlying sperm motility and their response to environmental conditions is critical for predicting the susceptibility of reproduction to climate change.

Localization of coral sAC along the entire length of the flagellum suggests an additional specialized role for this enzyme in motility. sAC also associates closely with the axoneme in sea urchins (64), where the large surface-area-to-volume ratio allows for rapid transmembrane signaling and direct contact with axonemal proteins (68). In addition, the other members of the motility pathway all localize almost exclusively to the sea urchin flagellum, including GC-A and CNGK (69), SLC9C1 (26), HCN (56), and CatSper (70), allowing for tight coupling of this signal transduction pathway. Although it remains to be determined where these proteins are expressed in coral sperm, it is likely that they similarly colocalize with coral sAC along the flagellum. In mouse sperm, sAC is expressed primarily in the midpiece but is not detected by immunocytochemistry in the principal piece (30). However, sAC activity has been observed in both of these compartments in mice, albeit with different kinetics (61), and the molecular mechanisms driving these differences remain to be described. Finally, the expression of coral sAC in the sperm head suggests it may play a role in the acrosome reaction, much like it does in sea urchins (64) and possibly in mammals (60). Interestingly, sea urchin sperm exhibit compartment-specific differences in sAC isoform expression, with sACT localizing to the head and sACFL along the flagellum (64). The functional significance of this partitioning remains unknown but could lead to differences in enzyme kinetics between the head and the flagellum that influence their disparate roles in the acrosome reaction and motility, respectively.

Expression of multiple sAC isoforms due to alternative splicing is common in metazoans (71), and corals are no exception (Fig. 2) (37). Coral sperm expressed multiple isoforms of sAC, including sACFL. That coral sACFL expression was restricted to the male germline, as it is in both mammals (30, 41) and echinoderms (64), suggests that there may be a conserved sperm-specific function of this isoform. However, the precise role of sACFL in cellular physiology remains enigmatic across all species examined to date. Interestingly, the autoinhibitory peptide described in mammalian sACFL (44) is absent in mcsAC and in sAC from all other coral species examined so far, which may contribute to the relatively high AC activity observed in corals (36) and highlights the need to understand more about the role of the sAC C-tail across metazoan species. Coral sperm also expressed several shorter isoforms, including an 100-kDa sAC isoform and two other small 45- to 55-kDa isoforms in low abundance. These smallest isoforms were also expressed in somatic coral tissues and may represent sACT, which is commonly expressed in both germline and somatic cells of bilaterians (41, 64). All together, these data suggest that sAC plays a conserved and complex role as a central regulator of sperm physiology across metazoa, and much work remains to unravel the many potential roles of this enzyme in sperm physiology of corals and other early-branching metazoans.

A comprehensive analysis of the molecular mechanisms underlying sperm activation in coral confirmed the expression and high structural conservation of the entire echinoderm sperm activation pathway in an early-branching metazoan. These results indicate that coral sperm activation couples environmental sensing to a cytoplasmic signaling pathway dependent on intracellular alkalinization and the central regulatory node of sAC-cAMP. The ability of sperm to remain in a quiescent state until they detect an egg nearby allows males to optimize their fertilizing capacity by saving their limited energy and increasing their chances of encountering eggs by using directional motility toward the cue (i.e., chemotaxis) (2). The majority of extant spawning marine invertebrates use chemotaxis, including corals, various other cnidarians, molluscs, echinoderms, and ascidians (72), and this capacity is critical for fertilization (Fig. 4). In each of these lineages, we find functional data supporting the conservation of the pH-sAC-cAMP pathway (Fig. 4) (2, 73). Genetic evidence for the coevolution of sAC, SLC9C1, and CatSper also links this pathway to even earlier branching phyla, including Ctenophora and Porifera (Fig. 4) (74). As copulation evolved in multiple lineages, this molecular mechanism was either lost (i.e., Nematoda) or it took on new roles, such as the sAC-dependent sperm maturation process in mammals (i.e., capacitation) (Fig. 4) (30). Characterizing the evolution of this pathway will allow us to better understand both the shared and divergent traits underlying male fertility in metazoans.

Evolutionary conservation of the sperm motility activation pathway across Metazoan phyla. (Left) Sperm release strategies among the phyla. Spawning refers to release of sperm into an external aquatic environment for internal or external fertilization. Copulation refers to direct sperm transfer and internal fertilization. (Middle) Phyla in which one or more species exhibit cAMP-dependent sperm motility. (Right) Phyla in which one or more species have sAC, SLC9C1, or CatSper expression confirmed in sperm (blue), encoded in the genome (teal), or absent from all available genomes (gray). White circles indicate that no data were found in the published literature.

Sexual reproduction is essential for the population growth, evolution, dispersal, and community dynamics of marine invertebrates (75). While climate change has impaired sexual reproduction across many marine taxa (76), the mechanisms driving these declines remain poorly understood. Ocean warming and acidification, two of the main climate change stressors affecting the ocean, may threaten sperm motility mechanisms that depend on precise intracellular pH by causing cytosolic acidification that may be prohibitively costly to overcome, thus preventing the signaling cascade necessary for motility. Cytosolic acidification may be especially costly to counteract for sperm, which have low cytoplasmic volume, limited energetic resources, and a brief lifespan (68). This could be an important bottleneck for population fitness, as sperm activation and motility are vital for fertilization across metazoan phyla. Importantly, the response of sperm to ocean acidification is nuanced, as both positive and negative shifts in sperm performance have been observed at the level of the individual male in molluscs and echinoderms (7780). This phenotypic diversity highlights the need to better understand the fundamental mechanisms that regulate sperm performance in order to predict how the fitness of corals and other marine invertebrates will be affected by a changing marine environment.

Eggsperm bundles were collected from Montipora capitata and allowed to break apart naturally in NaFSW (reference SI Appendix, Supplemental Methods for details). Sperm were loaded with 10 M SNARF-1-AM for 15 min in the dark at room temperature, and fluorescence was imaged using a confocal microscope with 561 nm excitation and dual emission (585 and 640 10 nm) at 25C. Sperm were imaged before and after addition of 20 mM NH4Cl every 20 to 40 s over the next 7 min, and at least 14 cells and up to 149 cells were analyzed per time point. Sperm pHi was calculated from the ratio (R) of SNARF1 fluorescence and an invivo calibration curve generated as previously described (81). A binary (motile versus nonmotile) motility score was also quantified from the fluorescence images, as nonmotile sperm appeared round with smooth edges (SI Appendix, Fig. S1A), whereas motile sperm had an oblong shape with an irregular border (SI Appendix, Fig. S1B). Sperm motility was also quantified following inhibition of sAC with 50 M KH7 relative to DMSO controls using phase contrast microscopy of 1) sperm in seawater, 2) sperm in NaFSW, and 3) sperm in NaFSW immediately following stimulation with NH4Cl.

Coral sperm suspended in NaFSW were treated with either 20 mM NH4Cl or 0.1% DMSO control, and cAMP production was stopped with the addition of HCl (0.17 N final concentration) at 0, 5, 30, 60, 120, and 500 s postexposure. Sperm were lysed by sonication, and cAMP content was quantified by enzyme-linked immunosorbent assay and normalized to total protein.

The presence of key components of the sperm motility activation pathway (sAC, PKA, SLC9C1, CatSper, GC-A, CNGK, and HCN) in corals was investigated by querying two M. capitata genomes (40, 47) using echinoderm or cnidarian homologs (reference SI Appendix, Supplemental Methods for more details). Each predicted gene coding sequence was then used as a query in a tBLASTn algorithm search of a sperm-specific RNA-seq database from M. capitata sperm (48). In silico comparisons of protein structure were carried out using the Clustal Omega multiple sequence alignment tool (82), prediction of transmembrane segments using the TMHMM server (83), and prediction of coiled-coil domains using the DeepCoil server (52).

Sperm total protein was extracted, and protein expression of mcsAC and mcPKA were detected by Western blotting using custom anti-coral sAC antibodies (37) and commercial anti-PKA antibodies (Cell Signaling 4782), respectively. To detect phosphorylated PKA substrates, sperm in NaFSW were stimulated with 20 mM NH4Cl and flash frozen after 0, 30, 60, or 120 s poststimulation and subjected to Western blotting with a phospho-PKA substrate antibody (RRXS*/T*; Cell Signaling 9642). Subcellular localization of mcsAC was determined by immunocytochemistry. Freshly collected sperm were fixed in 4% paraformaldehyde for 60 min at 4C, permeabilized in 0.3% Triton-X in phosphate-buffered saline for 3 min, and incubated with primary antibodies overnight at 4C. Cells were incubated with secondary antibodies for 1 h at room temperature in the dark, stained with NucBlue to label nuclei, and imaged using confocal microscopy.

A comparison of the reproductive strategies, sperm motility mechanisms, and sAC/sNHE/CatSper gene conservation was carried out through a search of the literature. Sources used in the compilation of the phylogenetic tree in Fig. 4 are described in SI Appendix, Fig. S5. All gene expression data were derived from ref. 74.

All study data are accessible as they are included in the article and/or supporting information.

We thank Crawford Drury, Hollie Putnam, Ariana Huffmyer, and the staff at the Hawaii Institute of Marine Biology for logistical support during coral spawning and Martin Tresguerrues for sharing coral sAC antibodies. The monoclonal antibodies, JLA-20 and E7, developed by the University of Iowa and the University of Colorado at Boulder, respectively, were obtained from the Developmental Studies Hybridoma Bank, created by the National Institute of Child Health and Human Development of the NIH and maintained at The University of Iowa, Department of Biology, Iowa City, IA. Sperm were collected under Special Activity Permits 2020-41 and 2021-41. All cartoons were created using BioRender.com and licensed for publication. This work was supported by the NSF Postdoctoral Research Fellowship in Biology 1812191 to K.F.S., NIH T32 Predoctoral Training Grant in Cell and Molecular Biology GM-07229 to L.A.-W., NSF-OCE 1923743 to K.L.B., and the Charles E. Kaufman Foundation New Investigator Award to K.L.B.

Author contributions: K.F.S. and K.L.B. designed research; K.F.S., L.A.-W., D.R.N., and K.L.B. performed research; K.F.S., L.A.-W., D.R.N., and K.L.B. analyzed data; and K.F.S., L.A.-W., and K.L.B. wrote the paper.

The authors declare no competing interest.

This article is a PNAS Direct Submission.

This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.2109993118/-/DCSupplemental.

Physiology

Bees with a taste for rotting flesh evolved to have guts like vultures, researchers find – USA TODAY

December 2, 2021 medical

Murder hornet nest found in Washington state

Officials in Washington state said Thursday they had destroyed the first Asian giant hornet nest of the season, which was located near the town of Blaine along the Canadian border. The Asian giant hornets are sometimes called murder hornets because they prey on other bees. (Aug. 26)

While most bees feed on pollen and nectar, scientists say some bees havedeveloped a taste for rotting flesh.

Researchers have learned that a stingless, tropical bee has evolved to have an extra tooth for biting and a gut that more closely resembles those of vultures in order to munch on meat, according to a studypublished last week in the American Society of Microbiologists journal mBio.

The reason? Likely due to intense competition for nectar, study co-author Laura Figueroa told USA TODAY.

"When asked where to find bees, people often picture fields of wildflowers.While true for almost all species, there is a group of specialized bees, also known as the vulture bees, that instead can be found slicing chunks of meat from carcasses in tropical rainforests," the authors wrote in the study titled, "Why Did the Bee Eat the Chicken?"

Only three bee specieshave evolved to exclusively eatmeat, though other speciesthat forage for pollen and nectar may also consume animal carcasses when they are available, according to the study.

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To study these species, researchers visited Costa Rica, where they hung raw chicken from branches to attract vulture bees.

They dodged bullet ants and problem solved when the chicken was stolen by other animals, said Figueroa, a postdoctoral research fellow at Cornell University. Researchers fromColumbia Universityand the University of California, Riverside also participated.

While stingless bees usually collect pollen in small baskets on their hind legs, the researchers saw vulture bees use the baskets to carry their meat, according to the study.

"They had little chicken baskets,"said Quinn McFrederick, a UC Riverside entomologist, in a statement to UC Riverside.

Researchers also noticed the bees preferred fresh meatthat was just starting to decompose and would avoid fully rotted meat.

Upon further study, they found the vulture bee gut microbiome is full of acid-loving bacteriasimilar to those found in vultures and hyenas, Figueroasaid. One of the bacteria types, calledLactobacillus, is also found in a lot of fermented foods like sourdough, while another bacteria found in vulture bee guts,Carnobacterium,is associated with flesh digestion.

Figueroasaid the bacteria helps protect the bees from pathogens found in rotting meat.

"For us, we can tell if we open our fridge and something has gone bad. And if you were to eat it, it's going to make you sick," she said. "So animals that are scavengers have evolved this microbiome and this physiology to deal with that bacteria and still be able to take advantage of that food source."

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Visual guide: Everything you need to know about the invasive 'murder hornet'

Figueroa said vulture bees still produce sweet, edible honey, though she has never tasted it herself.

But many carnivorousbees are not quite as sweet. Though they can't sting, some species can bite and a few "produce blister-causing secretions in their jaws, causing the skin to erupt in painful sores," entomologistDoug Yanega, one of the study authors, told UC Riverside.

Still,Figueroa sees the insects asbeautiful. When she was first introduced to the bees in 2015, she quickly "fell in love with them" and sought to do more research on the species, which was lacking studies.

"They're not scary even though they may sound a little bit scary," she said.

She said she hopes the study will encourageenvironmental conservation of the areas where the bees liveand that it"gets people excited about the diversity of animals in the world."

The research team plans to continue studying vulture bee microbiomes in hopes of documenting more of the bacteria, fungi and viruses in their bodies.

"There's still so much to learn about these bees," Figueroa said. "There's a lot of questions still to be answered."

Contact News Now Reporter Christine Fernando at cfernando@usatoday.com or follow her on Twitter at @christinetfern.

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Bees with a taste for rotting flesh evolved to have guts like vultures, researchers find - USA TODAY

Physiology

Warmer winter can cause problems for rice farmers with red rice, weedy rice – talkbusiness.net

December 2, 2021 medical

Capt. John Thurbers ship was badly damaged from a violent storm. It limped into the harbor in Charleston, South Carolina sometime in 1685. While the ship underwent repairs, Thurber met Dr. Henry Woodward and the two became friends.

As a token of gratitude, the captain gave the doctor a bag full of rice seeds he had acquired from Madagascar, just off the coast of southern Africa. It was the first time rice would be grown in the Western Hemisphere.

The Carolinas had a couple of advantages when it came to growing rice. Those colonies had fertile soil, plentiful water and African slaves that were experienced in growing rice on farms in their native continent.

Along with the rice also came another plant called red rice, a weed that often grows in rice paddies. Red rice in the field was a problem for rice growers, but at least it was easy to spot. But years of out-crossing with cultivated rice varieties has resulted in weedy rice, which appears in a spectrum of hues, some of which can blend in nicely with the crop.

But that camouflage is deceiving, and the result can be loss of both yield and rice quality, said Nilda Burgos, professor of weed physiology and molecular biology for the Arkansas Agricultural Experiment Station, the research arm of the University of Arkansas System Division of Agriculture.

The issue is that red rice is the same genus and species as cultivated rice, Burgos said. That leads to gene flow, when cultivated rice cross-pollinates with the weeds that survive from one year to the next. A problem may not manifest after a single rice season, but after repeated years of fraternization between weedy and domestic rice, the weeds present problems.

Burgos said she didnt expect to find a big problem with red rice at first because rice is self-pollinating. That slows the rate of cross-pollination, especially since the reproductive window of individual varieties is relatively narrow.

But we found that things begin to happen after multiple seasons, especially in fields where hybrids have been growing for many years, Burgos said.

Rice grains that fall out and are left in the field will grow up volunteers in following years. Outcrossing with weedy rice results in numerous offspring that manifest many hues of off-color rice, and varying maturity dates. This leads to a wider window for cross-pollination, which leads to more varieties of weedy rice.

The volunteers are bridges for outcrossing with weedy rice, Burgos said.

Because weedy rice often matures later than conventional varieties, its development is often stunted before grain maturity when cooler weather comes on in the fall. Second or third generations of weedy rice outcrosses only exist when it stays warm, Burgos said.

That makes weedy rice a bigger problem in countries with tropical climates, Burgos said. But its also a problem as warm weather stretches longer into fall in the U.S.

When it comes to global warming, weeds are going to love it, Burgos said. Outcrossing and herbicide resistance will become worse.

The rise of weedy rice is not anyones fault, she said. Its a combination of factors, including plants, weather, climate, economics, available agricultural technology, available knowledge and farming practices.

Hybrids have passed along herbicide resistance to weedy rice, Burgos said.

Hybrid rice is more compatible with red rice and the outcrossing rate is higher, Burgos said. The outcrossing rate in hybrids is double that of conventional rice varieties.

Thats still low, because of rice being self-pollinating, Burgos said. But it means that it takes fewer seasonal cycles before problems begin to mount up.

Besides causing headaches for weed control, the varying hues of weedy rice mar the consistent white color desired at the rice mills, Burgos said. That causes devaluation of the crop, and a discounted price paid to the farmers.

Being the same species as cultivated rice means that weedy rice is also competing with the crop for resources throughout the growing season, robbing the crop of nutrients and water, Burgos said.

The variability in maturity date also means the weedy rice may be overly mature or under-mature at harvest. Grains from overly mature weedy rice shatter in the field, leaving seed that will grow up as weeds in the following season, or during milling, damaging a crops milling yield.

Under-mature weedy rice at harvest means moisture content will be too high, complicating rice drying.

Plant height of weedy rice is consistent in the first generation, Burgos said. But it begins to vary in succeeding generations.

With all this going on, Burgos said, weedy rice wreaks havoc in the rice field. Burgos quantified yield loss for varying varieties and growing conditions. The weeds also result in lower rice quality and, in worst cases, can severely damage the whole crop.

Avoiding damage from weedy rice begins with zero tolerance weed management, Burgos said. Dont leave anything in your field. And dont forget the edges of the fields.

Many growers clean up their fields thoroughly, but neglect the edges and ditches, Burgos said. The following year, weedy rice sprouts up at the peripheries of rice fields and spreads in from the edges.

Rice is a top agricultural commodity in the Natural State.

Arkansas rice exports accounted for $722 million of the states total of $3.1 billion in agricultural exports. Despite the states position as the top rice producing and exporting state, farmers in 2021 dropped the number of rice acres in Arkansas. Decade high prices for corn and soybeans prompted the shift. Arkansas rice growers planted about 18% fewer acres this year, falling from about 1.46 million acres in 2020 to about 1.24 million acres. Nationally, rice acreage fell by about 10%, from 3 million acres planted in 2020 to about 2.7 million acres in 2021. This includes long, short and medium grain rice.

Rotating hybrid rice with conventional varieties can also slow gene flow and inhibit development of herbicide resistant weeds, Burgos said. Rotating rice with other crops, like soybeans, and the different weed control strategies used with those plants can help keep rice fields clean. She also advises rotating weed control strategies.

Make sure, whatever you use, you leave no weedy rice in the field. Farmers are seeing more resistant weedy rice, Burgos said. Any field that has had Clearfield in it for many years will be more likely to see it.

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Physiology

A Nobel Prize with a connection to UB research – UB Now: News and views for UB faculty and staff – University at Buffalo Reporter

November 4, 2021 medical

On Oct. 4, the Nobel Prize for Physiology or Medicine was awarded to two researchers for their work in identifying the proteins responsible for providing our ability to sense heat and touch.

These were milestones to commemorate, and well-deserved by the researchers who made the discoveries: Dr. David Julius at the University of California, San Francisco, and Dr. Ardem Patapoutian at Scripps Research in La Jolla, California.

With regard to sensing touch, Dr. Patapoutian won the prize for identifying Piezo proteins, which are a type of ion channel on the surface of cells that respond to pressure and stretching.

This can be the pressure or stretching felt as we slide our finger across the surface of a table, or the pressure in our arteries that occurs with each heartbeat. It can be the stretch felt in our lungs when we take a deep breath, or the pain felt by the inflammation caused by a mosquito bite.

The touch sensitivity award is significant to the UB community because the category of ion channels that provide this sensitivity were first observed right here in Buffalo.

Forty years ago, Dr. Frederick Sachs, SUNY Distinguished Professor in the Department of Physiology and Biophysics in the Jacobs School of Medicine and Biomedical Sciences at UB, used miniature glass pipettes to suck on the surface of skeletal muscle cells. And in so doing he recorded for the first time the tiny electrical currents that were produced by mechanosensitive ion channels that were most likely Piezo channels.

This seminal publication (Journal of Physiology, London, 1984, 352, 685-701) opened the door to the field of touch-pressure sensitivity. And this first paper was followed by many publications by Dr. Sachs and others over the next 25 years, using his technique to investigate how mechanosensitive ion channels provide many different cell types with the ability to feel their surroundings.

Additional publications by Dr. Sachs and colleagues showed the role of these ion channels in pathology for diseases like vascular disease, cardiac arrhythmias, muscular dystrophy, sickle cell anemia and cancer. Scientists soon realized that disease in any form can change the way tissues and cells respond to stretch and pressure in a variety of ways through pressure from a growing tumor pressing on the surrounding healthy tissue; through a heart arrhythmia that causes the heart muscle to contract with unsynchronized force; or through long-term stiffening of arteries that are under prolonged increased blood pressure from stress.

For many years these channels were being studied in normal physiology and disease using Dr. Sachs technique, but without knowing the identity of the protein that actually provided the ability to respond to stretch and pressure.

It wasnt until Dr. Patapoutian discovered the amino acid sequence of these channels that we knew their identity. And this discovery allowed researchers to investigate how expression of the channels in different tissues changes during normal development and their abnormal function contributes to disease. It also allowed more detailed studies of how the channels respond to stretch forces in different environments.

The role of these channels in disease led Dr. Sachs to search for blockers as a way to ameliorate negative effects of the overactivity of these channels.

Dr. Sachs teamed with me and Dr. Philip Gottlieb, also researchers in the Department of Physiology and Biophysics, to search for compounds that could block the channels. We hunted for compounds in spider and scorpion venom, and discovered an effective blocker of Piezo channels in the venom of the Chilean Rose tarantula and called it GsMTx4.

We then discovered the compounds unusual method of blocking, which so far has proven difficult to duplicate. To improve the lives of patients suffering from disease, we launched a biomedical company called Tonus Therapeutics to develop this blocker, which is now made as a synthetic version of the original tarantula venom compound.

The Sachs/Suchyna/Gottlieb lab continues to study pressure/touch sensitivity here at UB. We use a variety of novel techniques to provide new insights into the role of Piezo channels in living systems and into the development of therapeutic strategies to treat disease. The recognition of the Nobel award committee to pressure/touch sensitivity as a milestone in biology and medicine will bring welcomed exposure to the field for funding and help to attract young scientists into this important area of research.

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A Nobel Prize with a connection to UB research - UB Now: News and views for UB faculty and staff - University at Buffalo Reporter

Physiology

Penn study illuminates the biology of common heart disorder – EurekAlert

November 4, 2021 medical

Researchers at Penn Medicine have made a major advance in understanding the biology of a common, puzzling, and often fatal heart disorder, dilated cardiomyopathy (DCM), which features the enlargement of the heart and a progressive decrease in its function, for reasons other than cardiovascular disease. DCM is estimated to affect at least hundreds of thousands of people in the United States. The largest single known cause, accounting for an estimated 10 to 20 percent of cases, involves the mutation of the gene that encodes a key heart-muscle protein called titin.

Titin (pronounced titan) is a giant among proteins, and unfortunately its enormity has made it hard to study. How titin mutations lead to DCM has therefore been largely a mystery. But the Penn Medicine researchers, who report their findings today in Science Translational Medicine[LB1], used an array of sophisticated methods to overcome the usual technical hurdles. They found that titin mutations in DCM patients lead to two key abnormalities in heart muscle cells: a shortage of normal-length titin, and the accumulation of mutant, truncated titin fragmentspointing to the possibility that both of these abnormalities drive heart dysfunction in DCM.

These findings change how we look at this genetic form of DCM and give us new directions to pursue for possible future therapies, said study co-senior author Zoltan Arany, MD, PhD, Samuel Bellet Professor of Cardiology at the Perelman School of Medicine at the University of Pennsylvania. Aranys co-senior author is Benjamin L. Prosser, PhD, an associate professor of Physiology.

There is a strong need for a disease-specific treatment for DCM, since the disorder is both common and lethal. It often leads, within a few years, to heart failure, and only about half of DCM patients live five years after their diagnosis. Many who survive do so by receiving heart transplants.

Developing an effective therapy has been a real challenge, however, given the lack of understanding of DCMs underlying biology. Pregnancy, the use of alcohol and other recreational drugs, certain types of infection, and gene mutations, have all been linked to DCMand there are hints that in many cases a combination of factors triggers this diseasebut the precise causes in most individual cases are obscure. Even the mechanism by which titin gene mutations cause DCM has been unclear.

In principle, these causative mutations offer researchers an opportunity to discover the details of how DCM arises. In practice, the size of the affected protein, titin, the largest known protein in biologyhundreds of times larger than many other common proteinshas made it uniquely hard to study. In particular, prior research has been unable to determine whether titin mutations in DCM patients cause heart disease through some direct toxic effect of mutant titin protein, or due to a shortage of normal titin protein.

In the new study, Arany and his colleagues tackled this question, and found evidence supporting both of these mechanisms.

A pathbreaking study

The titin mutations that are often linked to DCM are in the titin-encoding gene TTN, and are called truncatingshortenedvariants in TTN, or TTNtvs. Most genes in our genomes are inherited as a pair, one copy from the mother and one from the father, and DCM patients with TTNtvs typically have one normal copy of TTN to go with the abnormal copy.

Arany and his colleagues examined 184 failing hearts taken out of DCM patients during transplants by co-author Kenneth Margulies, MD, research director of Heart Failure/Transplantation and a professor of Medicine and Physiology at Penn. The researchers found TTNtvs in 22 of the hearts and, with an innovative set of techniques, detected abundant truncated titin fragments, even though prior studies of TTNtv hearts did not find them. That discovery reopens the possibility that these fragments are contributing to DCM by harming heart muscle cells.

In another novel finding, the researchers determined that levels of normal titin were about 30 percent lower in TTNtv-containing heart muscle, suggesting that a shortage of normal titin may also be a contributor to disease.

The study yielded many other findings, such as the observation that the severity of DCM doesnt seem to depend on the parts of titin affected by TTNtv mutations. Altogether, the study represents a leap forward in this fieldone that sends researchers along many new lines of investigation, which could ultimately yield the first DCM-specific treatments.

If it turns out that these chopped titin proteins are the chief cause of trouble, for example, wed want to design therapies to get rid of those proteins, Arany said. With these findings, were aiming in a different direction.

The research was supported by grants from the National Institutes of Health (R01-HL133080, R01-HL126797, AR 53461-12, R01 AG17022, R01 HL089847, R01 HL105993, R01 HL13308), the Gund Family Fund, and the Department of Defense (W81XWH18-1-0503).

Science Translational Medicine

Observational study

Human tissue samples

Truncated titin proteins in dilated cardiomyopathy

3-Nov-2021

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.

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Physiology

The trouble of being tall – Vet Candy

November 4, 2021 medical

The giraffe is a truly puzzling animal. With its exceptional anatomy and suite of evolutionary adaptations, the giraffe is an outstanding case of animal evolution and physiology. Now, an international team of researchers from the University of Copenhagen and Northwestern Polytechnical University in China have produced a high-quality genome from the giraffe and investigated which genes are likely to be responsible for its unique biological features.

The extraordinary stature of the giraffe has led to a long list of physiological co-adaptations. The blood pressure of the giraffe, for instance, is twice as high as in humans and most other mammals to allow a steady blood supply to the lofty head. How does the giraffe avoid the usual side effects of high blood pressure, such as severe damage to the cardiovascular system or strokes?

The team discovered a particular gene - known as FGFRL1 - that has undergone many changes in the giraffe compared to all other animals. Using sophisticated gene editing techniques they introduced giraffe-specific FGFRL1 mutations into lab mice. Interestingly, the giraffe-type mice differed from normal mice in two important aspects: they suffered less cardiovascular and organ damage when treated with a blood pressure increasing drug, and they grew more compact and denser bones.

- "Both of these changes are directly related to the unique physiological features of the giraffe - coping with high blood pressure and maintaining compact and strong bones, despite growing them faster than any other mammal, to form the elongated neck and legs.", says Rasmus Heller from the Department of Biology, University of Copenhagen, one of the lead authors on the study.

Giraffe's can't get no sleep

While jumping out of bed for (some) humans might be an effortless and elegant affair, this is definitely not the case for the giraffe. Merely standing up is an a lengthy and awkward procedure, let alone getting up and running away from a ferocious predator. Therefore, giraffes have evolved into spending much less time sleeping than most other mammals.

- Rasmus Heller elaborates: "We found that key genes regulating the circadian rhythm and sleep were under strong selection in giraffes, possibly allowing the giraffe a more interrupted sleep-wake cycle than other mammals".

In line with research in other animals an evolutionary trade-off also seem to be determining their sensory perception, Rasmus continues:

- "Giraffes are in general very alert and exploit their height advantage to scan the horizon using their excellent eyesight. Conversely, they have lost many genes related to olfaction, which is probably related to a radically diluted presence of scents at 5m compared to ground level".

A model of evolutionary mechanisms--and perhaps even human medicine?

These findings provide insights into basic modes of evolution. The dual effects of the strongly selected FGFRL1 gene are compatible with the phenomenon that one gene can affect several different aspects of the phenotype, so called evolutionary pleiotropy. Pleiotropy is particularly relevant for explaining unusually large phenotypic changes, because such changes often require that a suite of traits are changed within a short evolutionary time. Therefore, pleiotropy could provide one solution to the riddle of how evolution could achieve the many co-dependent changes needed to form an animal as extreme as a giraffe. Furthermore, the findings even identifies FGFRL1 as a possible target of research in human cardiovascular disease.

- "These results showcase that animals are interesting models, not only to understand the basic principles of evolution, but also to help us understand which genes influence some of the phenotypes we are really interested in - such as those related to disease. However, it's worth pointing out that genetic variants do not necessarily have the same phenotypic effect in different species, and that phenotypes are affected by many other things than variation in coding regions.", says Qiang Qiu from Northwestern Polytechnical University, another lead author on the study.

The results have just been published in the prestigious scientific journal,Science Advances.

###

Physiology

Protein in the brain uses energy status to influence maturation, body size, new research shows – University of Michigan News

November 4, 2021 medical

Scientists have identified how a protein in the brain uses information about the bodys energy balance to regulate growth rate and the onset of puberty in children.

The research, published Nov. 3 in the journal Nature, centered on the melanocortin 3 receptor (MC3R), a member of a family of proteins that have long been known to play central roles in metabolism and energy balance.

University of Michian physiologist Roger Cone and colleagues discovered the MC3R gene more than 20 years ago and demonstrated that mice lacking this protein exhibit reduced linear growth, reduced lean mass and increased obesity. Subsequent studies published by Cones group also demonstrated a role for the receptor in regulating the interaction between reproduction and energy state, including the increased feeding and weight gain during pregnancy.

Now, an international team of scientists led by Sir Stephen ORahilly at the Wellcome-MRC Institute of Metabolic Science, University of Cambridge, has revealed for the first time how defects in the MC3R translate to humanswith results strikingly similar to the findings in mice.

The ORahilly team reports identification of the first individual with mutations in both copies of the MC3R gene, leaving the person with no functioning MC3R. Such cases are extremely rare, perhaps occurring in as little as one in a billion people. This individual showed phenotypes, or physical traits, that were nearly identical to mice with no MC3R.

Using data from UK Biobank and the Avon Longitudinal Study of Parents and Children, the team analyzed the phenotypes in volunteers with mutations in one copy of the gene that encodes the MC3R. These individuals displayed shorter body height and reduced lean mass compared with those who had no MC3R mutations.

In terms of melanocortins, every phenotype that we have observed in the mouse has ultimately been found to be replicated in humans, said Cone, director of the U-M Life Sciences Institute and an author of the new study. This direct correlation between animal models and humans is not always the case; but this research shows that mice are a near-perfect model for studying human syndromes related to melanocortin receptors.

Additionally, ORahilly discovered one new phenotype in people with MC3R mutations: a long delay in the onset of puberty in the patient lacking MC3R, and subtle but significant delays in volunteers from the UK Biobank with mutations in only one copy of the gene. Due to the discovery of only a single patient with loss of both copies of the MC3R gene, the researchers also used mouse gene knockout models to confirm and further understand the findings.

New data generated by the Cone lab and collaborator Richard Simerly at the Vanderbilt School of Medicine, and published in this latest study, verify this effect and also argue that MC3R plays a role in communicating nutritional deprivation to the reproductive axis.

When mice are fasted for 24 hours, the MC3R detects the lack of energy stores in the body and relays that information to the part of the brain that regulates reproductive cycles. In normal mice, the reproductive cycles halt until energy stores return to normal, post-fasting. In mice with no MC3R, however, there is no change to the reproductive axis following fasting, indicating that communication about the energy balance has stopped.

These types of experiments give us important new understanding of the bodys metabolic and reproductive pathways, but they obviously cannot be done in humans, said Cone, who is also a professor of molecular and integrative physiology at the U-M Medical School. This research illustrates the critical role of animal models for studying the fundamentals of physiology, which can then be translated to human health and disease.

The research was supported by the National Institutes of Health (United States), the UK Medical Research Council, Wellcome and the National institute for Health Research (United Kingdom).

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