A new study led by UC Davis MIND Institute researchers found a distinct DNA methylation signature in the cord blood of newborns who were eventually diagnosed with autism spectrum disorder (ASD). This signature mark spanned DNA regions and genes linked to early fetal neurodevelopment. The findings may hold clues for early diagnosis and intervention.

"We found evidence that a DNA methylation signature of ASD exists in cord blood with specific regions consistently differentially methylated," saidJanine LaSalle, lead author on the study and professor of microbiology and immunology at UC Davis.

The studypublished Oct. 14 inGenome Medicinealso identified sex-specific epigenomic signatures that support the developmental and sex-biased roots of ASD.

The U.S. Centers for Disease Control and Prevention (CDC) estimates that one in 54 children are diagnosed with ASD, a complex neurological condition linked to genetic and environmental factors. It is much more prevalent in males than females.

The epigenome compounds do not change the DNA sequence but affect how cells use the DNA's instructions. These attachments are sometimes passed on from cell to cell as cells divide. They can also be passed down from one generation to the next. The neonatal epigenome has the potential to reflect past interactions between genetic and environmental factors during early development. They may also influence future health outcomes.

The researchers also analyzed the umbilical cord blood samples taken at birth from the delivering mothers. They performed whole-genome sequencing of these blood samples to identify an epigenomic signature or mark of ASD at birth. They were checking for any patterns of DNA-epigenome binding that could predict future ASD diagnosis.

They split the samples into discovery and replication sets and stratified them by sex. The discovery set included samples from 74 males (39 TD, 35 ASD) and 32 females (17 TD, 15 ASD). The replication set was obtained from 38 males (17 TD, 21 ASD) and eight females (3TD, 5 ASD).

Using the samples in the discovery set, the researchers looked to identify specific regions in the genomes linked to ASD diagnosis. They tested the DNA methylation profiles for DMRs between ASD and TD cord blood samples. They mapped the DMRs to genes and assessed them in gene function, tissue expression, chromosome location and overlap with prior ASD studies. They later compared the results between discovery and replication sets and between males and females.

"Findings from our study provide key insights for early diagnosis and intervention," LaSalle said. "We were impressed by the ability of cord blood to reveal insights into genes and pathways relevant to the fetal brain."

The researchers pointed out that these results will require further replication before being used diagnostically. Their study serves as an important proof of principle that the cord blood methylome is informative about future ASD risk.

Reference: Mordaunt CE, Jianu JM, Laufer BI, et al. Cord blood DNA methylome in newborns later diagnosed with autism spectrum disorder reflects early dysregulation of neurodevelopmental and X-linked genes. Genome Medicine. 2020;12(1):88. doi:10.1186/s13073-020-00785-8.

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