Children affected by Batten disease are born with no symptoms and develop normally, learning to walk, talk, and interact with others.Between 5 and 8years of age, however, they start to regress."The first symptom that leads parents to seek medical attention for their child is a loss of vision caused by retinal degeneration.This is followed by cognitive regression characterized by speech and mobility impairment.The life expectancy for people with the disease is usually around 30 years," explains Lefranois, who has been working on Batten disease for more than ten years.

A key protein

Professor Lefranois and his team in Laval are delving into the cellular biology of the CLN3 protein, which has been synthesized with the help of its namesake gene, in order to better understand the protein's function and identify therapeutic targets.They recently published findings about a key role played by CLN3 in the Journal of Cell Science.In the absence of the disease, CLN3 ensures a constant supply of proteins to the endosome, an intracellular compartment that serves as a sorting centre for proteins within the cell.

"Under this cellular process, a receptor acts as a truck that carries proteins from the Golgi apparatus, the production factory, to the sorting centre.Thanks to CLN3, this truck normally returns to the Golgi to pick up another load of proteins in an ongoing cycle," the researcher explains."In the presence of the mutations, however, the truck doesn't make the return trip.Instead, it is redirected to the lysosomes, where it's broken down as cellular waste."

Because the receptor is degraded, the proteins vital to lysosome function can't reach their destination.In consequence, these organelles are no longer able to break down cellular waste, so they accumulate and cause cellular degeneration."We think that children with the disease develop normally in their early years because their cells compensate by making more trucks.It's possible that the cells can't keep up, so the system becomes dysfunctional and starts to degrade," adds Professor Lefranois.

Professor Lefranois is working with a team of European researchers to re-establish normal CLN3 function with a promising drug. The aim is to prevent degradation of the receptor so it can continue carrying proteins.

Worldwide, it is estimated thatone person in 100,000has Batten's disease in all its forms.

About the study

The article entitled CLN3 regulates endosomal function by modulating Rab7A effector interactions, by Seda Yasa, Graziana Modica, Etienne Sauvageau, Abuzar Kaleem, Guido Hermey, Stephane Lefrancois, was published in the Journal of Cell Science. The research was supported by the Joint Programme on Neurodegenerative Diseases Grant, the Canadian Institutes of Health Research, the Canadian Foundation for Innovation, the National Contest for Life Foundation Germany and by the Deutsche Forschungsgemeinschaft, the Fondation Armand-Frappieret du Fonds de recherche du Qubec Sant (FRQS).DOI : 10.1242/jcs.234047

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SOURCE Institut National de la recherche scientifique (INRS)

For further information: Audrey-Maude Vzina, Communications, INRS, 418-254-2156 (cell), [emailprotected]

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Rare disease in children: the key role of a protein revealed - Canada NewsWire