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This Week in PLOS: Nov 3, 2014

In PLOS Genetics, Canadian researchers explore contributions that de novo mutations make to cases of severe or more moderate intellectual disability. Through exome sequencing on 41 individuals with intellectual disability and their unaffected parents, the team narrowed in on 81 de novo mutations that appear to impact protein-coding sequences or splice sites. The analysis highlights alterations in a dozen genes implicated in intellectual disability and indicates that affected individuals tend to carry higher-than-usual burdens of new nucleotide substitutions or de novo mutations that interfere with the function of resulting proteins.

North American house sparrows have been co-evolving with West Nile virus since the virus was first detected on the continent in 1999, according to a study in PLOS Neglected Tropical Diseases. Investigators from the Centers for Disease Control and Prevention in Fort Collins, Colorado, and other centers in the US looked at West Nile virus infectiousness, genotype, and blood concentration in house sparrows caught in a Colorado county in 2012 and 2013. For instance, the study suggests that the sparrows may be developing resistance to a West Nile virus genotype called NY99 — the form of the virus identified during the earliest US outbreak of the virus. On the other hand, the analysis hints that the viruses may be ratcheting up their pathogenicity in the house sparrows.

A PLOS One paper describes microRNAs identified in tissues from the marine medaka fish under normal or low oxygen conditions. By sequencing small RNAs from male and female medaka brain, liver, and gonad tissue, Chinese researchers detected hundreds of medaka miRNAs showing widespread or tissue-specific expression. Under the low oxygen conditions, for example, female fish showed lower-than-usual levels of three miRNA, while hypoxic male fish had higher testis expression of at least one miRNA. "Because miRNA expression is highly conserved between marine medaka and other vertebrates," the study's authors say, "marine medaka may serve as a good model for studies on the functional roles of miRNAs in hypoxia stress response and signaling in marine fish."