Background:  Three studies published today in Nature demonstrate the genetic complexity of autism spectrum disorders (ASD). Each study analyzed genes of ASD families by sequencing their exomes, the sets of genes within the genome that encode proteins.  This allowed them to search for single-letter DNA mutations that arise spontaneously, or de novo, and are not inherited from either parent.  Together, the studies analyzed the exomes of 622 family trios (two unaffected parents and one affected child) and 250 unaffected sibling controls.

What’s New:  The three research teams found hundreds of mutated genes, independently replicating six (GRIN2B, LAMC3, SCN1A, SCN2A, KATNAL2, CHD8) by screening other populations of ASD patients and controls.  Additionally, they found that de novo autism-linked mutations are four times more likely to occur on the gene copies inherited from the father than from the mother.  They also confirmed that genes contributed from older fathers have higher rates of de novo mutations.

Why It’s Important:  Together, new estimates of autism risk genes reach as high as 1,000.   Many of these autism risk genes function similarly, suggesting identification of convergent molecular networks as one approach for tackling the enormous genetic heterogeneity of autism.

Genetics

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