Cerebellum size shows tenuous genetic link to autism | Spectrum

Cerebellar control: The cerebellum, an ancient and understudied brain region, may be less linked to autism than previously thought.

According to a new study, certain genomic areas that help determine the size of the cerebellum are associated with autism, schizophrenia and bipolar disorder. But inherited genetic variants across the genome that also influence the size of the cerebellum are not.

The cerebellum sits at the base of the skull, below and behind the much larger brain. It coordinates movement and may also play a role in social cognition and autism, according to previous research.

The new work analyzed genetic information and structural brain scans from more than 33,000 people from the UK Biobank, a biomedical and genetic database of adults aged 40-69 living in the UK. A total of 33 genetic sequence variants, known as single nucleotide polymorphisms (SNPs), have been associated with cerebellar volume differences.

Only one SNP overlapped with those linked to autism, but the association should be explored further in other cohorts, says lead researcher Richard Anney, senior lecturer in bioinformatics at Cardiff University in Wales.

“There are a lot of caveats as to why it might be worth following,” says Anney. “But from these data alone, it does not tell us that there is a major link between [autism] and cerebellar volume.

Until now, cognitive neuroscientists have largely ignored the cerebellum, says Jesse Gomez, assistant professor of neuroscience at Princeton University, who was not involved in the work. The new study represents a first step in better understanding genetic influences on the brain region and its role in neurodevelopmental conditions, he says.

“It’s a fun journal,” Gomez says. “This is the start of what is an exciting revolution in the field.”

OOf the 33 inherited variants found by Anney’s team, 5 had not been significantly associated with cerebellar volume. They estimated that the 33 variants account for about 50% of the observed cerebellar volume differences between participants.

Anney and her team then compared their analysis with previous genome-wide association studies of SNPs linked to autism, schizophrenia, bipolar disorder, depression and hyperactivity disorder. attention. Of the 33 variants they reported, 1 had previously been associated with autism, 5 with schizophrenia, 2 with bipolar disorder and 1 with attention deficit hyperactivity disorder.

Overall, however, genetic variants associated with cerebellar volume were not significantly related to any of these conditions.

The findings were published in Molecular psychiatry in January.

The sample size is small for a genome-wide association study, which challenges some of the findings, says Tinca Polderman, associate professor of child and adolescent psychiatry at UMC. from Amsterdam in the Netherlands, who did not participate in the work. . Genetic correlations between the volume of the cerebellum and other brain lobes were unusually weak, for example, she says.

“I am not completely convinced by the results of this study,” Polderman wrote in an email to Spectrumadding that replicating the results in a larger cohort would help.

And the analysis doesn’t rule out a role for the cerebellum in autism or other conditions, Gomez says. There could be many genetic factors that influence the function of the cerebellum without affecting its overall volume, he says.

“I’m sure the cerebellum plays a role in many disorders. It is strongly connected to the brain,” says Gomez. “How you can analyze this data set is potentially a bit limited.”

Anney and her team plan to repeat the analysis in cohorts with different demographic characteristics than the UK biobank, such as a group including children.

Cite this article: https://doi.org/10.53053/FACT9868

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