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This Week in PLOS: Apr 17, 2017

In PLOS Genetics, researchers from Norway and Sweden describe forms of selective constraint involving connectivity between co-expression networks. Using RNA sequencing and genome re-sequencing, the team profiled gene expression in buds from a natural aspen (Populus tremula) tree population as they transitioned from winter buds to flushing buds. With these data, the group also narrowed in on almost 164,300 expression quantitative trait loci affecting more than 6,200 genes, teased out apparent co-expression networks, and gauged selective constraints associated with various genes. "Our results suggest that purifying selection plays an important role in buffering the transcriptional network against large perturbations," the authors note, "and that natural variation in gene expression is more prevalent in genes of low network connectivity as a result of relaxed selective constraint." 

Bird phylogenetic diversity follows a gradient that varies by latitude, according to a paper in PLOS Biology. A team from the American Museum of Natural History, Louisiana State University, and elsewhere tapped mitochondrial sequence data for nearly 17,600 individual birds from 210 New World species for its analysis, demonstrating that average phylogeographic diversity tended to wane with rising latitude in ways that could not be explained by factors such as species ecology, life history, or habitat alone. "Tropical species are older and harbor more phylogeographic structure," the researchers say, "whereas temperate species are younger and have signatures of lineage loss, suggestive of pervasive impacts of environmental instability at high latitudes."

Finally, investigators from Germany, Italy, and Sweden present findings from an association study aimed at assessing inherited germline in genes previously reported as somatically mutated in sporadic forms of the thyroid cancer. As it reports in PLOS One, the team started by comparing genotype patterns in more than 1,500 individuals with sporadic, well-differentiate thyroid cancer from Italy, and 1,610 unaffected control individuals from the same population, identifying five potential protective SNPs and three rare variants with potential ties to disease risk. After a validation and meta-analyses using data for another 691 cases and 498 controls, the researchers verified a risk SNP in the GNAS gene and protective SNP in APC.