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PNAS Studies Look at Diabetes Susceptibility, S. Aureus Subpopulations, More

Researchers at Columbia University and the University of Pennsylvania describe an apparent role for the chromosome 15 gene C2CD4A in insulin secretion from pancreatic beta-cells and related susceptibility to type 2 diabetes (T2D). Starting with a locus associated with T2D in prior genome-wide association studies, the team searched for overlapping super-enhancers of FoxO1, which has been implicated in beta-cell dysfunction. In the process, the investigators picked up a FoxO1 super-enhancer falling in C2CD4A — a largely uncharacterized gene with enhanced beta-cell expression. Follow-up mouse experiments suggested that the absence of C2CD4A dials down insulin secretion by beta cells, prompting the authors to speculate that "[a]s a regulator of insulin secretion, C2cd4a may be an attractive new target for diabetes therapies."

An Australian team takes a look at the unstable chromosomes and chromosome rearrangements behind so-called "small colony variants" (SCVs) — S. aureus sub-populations implicated in infections that persist or recur. The researchers did genome sequencing on a spontaneous SCV that arose from S. aureus bugs carrying a rifampicin resistance mutation, uncovering chromosome rearrangements involving type 1 restriction modification system genes that appeared to contribute to lower-than-usual virulence — but enhanced immune evasion — in infected host cells. With genome sequences from 29 more S. aureus isolates, quantitative PCR, and long-read amplicon sequencing, the authors saw signs that SCVs may stem from "asymmetric chromosome inversion and the activation of prophage-encoding genes used for immune evasion."

University of Florida, Stanford University, and University of California, Davis, researchers uncover waning phylogenetic diversity in a California grassland community after almost two decades of diminishing, less-consistent moisture, known as a 'precipitation whiplash.' Using information from the Open Tree of Life and standardized species names, team tracked phylogenetic diversity over time, space, precipitation patterns, and more at the University of California McLaughlin Reserve site, documenting a phylogenetic diversity dip over small areas, coupled with more stable phylogenetic diversity over broader areas. "Our study represents one of the first demonstrations that climate-induced loss of diversity may extend beyond the level of the species," they write, while pointing to "the positive value of physically and biologically complex landscapes as refuges for maintaining biodiversity in a changing world."