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This Week in PNAS: Oct 8, 2014

In the early edition of the Proceedings of the National Academy of Sciences, a Massachusetts General Hospital- and Broad Institute-led team take a look at autism spectrum disorder symptoms and severity in relation to inherited and de novo risk variants in affected individuals. The researchers considered 2,000 ASD cases for the study, focusing on individuals with no affected siblings. When they considered de novo loss-of-function mutations by exome sequencing on a subset of parent and affected child trios — together with information on the individuals' behavior, language skills, cognitive performance, family history, and more — the researchers saw that high functioning ASD cases often involved familial influence, whereas cases with more severe cognitive, language, and/or behavioral impairments frequently stemmed from de novo loss-of-function mutations.

Another group of investigators from Massachusetts General Hospital, the Broad, and elsewhere focus on functional consequences of ASD-related truncating mutations in the chromodomain helicase enzyme-coding gene CHD8, which was already linked to ASD. The researchers identified almost 1,800 differentially expressed genes through RNA sequencing on neural progenitor cells with lower-than-usual CHD8 levels, including shifts in expression for some genes linked to ASD in the past. Meanwhile, their CHD8 targeted chromatin immunoprecipitation sequencing on similar cells revealed CHD8 binding sites adjacent to nearly 5,700 genes.

A team from the UK, US, and Russia argue that the apparent heritability of educational attainment level is due to several traits with genetic underpinnings, rather than solely reflecting intelligence levels. The researchers assessed test scores for more than 13,300 twins who'd taken a standardized test given to individuals in the UK at the age of 16, along with information on the individuals' other behavioral traits and personality features. While intelligence did have a significant effect on the individuals' test scores, several other heritable features such as personality and an individual's confidence in his or her abilities contributed as well, the study's authors say, suggesting "high heritability of educational achievement reflects many genetically influence traits, not just intelligence."