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This Week in PNAS: May 10, 2016

In the early, online edition of the Proceedings of the National Academy of Sciences, researchers from the US and Canada explore potential ties between DNA methylation and persistent effects of intensive or standard treatment — dubbed metabolic memory — in individuals with type 1 diabetes. The team initially profiled genome-wide methylation patterns in blood samples collected more than a decade apart from dozens of individuals with type 1 diabetes who had developed vascular complications such as retinopathy after receiving conventional therapy. The search uncovered lasting methylation shifts compared with vascular complication-free type 1 diabetes patients who had undergone intensive glycemic control-based therapy, which the study's authors call "direct evidence of a relationship between epigenetic (DNA methylation variations) and human metabolic memory."

Brandeis University researchers describe a microRNA called mir-276a that appears to contribute to circadian rhythm control in the fruit fly Drosophila melanogaster. The team found that the miRNA — identified using a screen for circadian rhythm alterations in flies overexpressing individual miRNAs — varies in its abundance over the course of a day in Drosophila clock neurons. When they meddled with the regulation of this process, the investigators led to a decline in circadian rhythm regularity and a rise in levels of the protein encoded by a key clock gene known as timeless (tim). "Taken together," the study authors write, "our data indicate a previously unidentified post-transcriptional pathway that regulates tim expression."

Finally, an international team led by investigators in Austria and the UK presents a population study of dromedaries from around the world. The researchers retraced dromedary phylogenetic relationships using mitochondrial and nuclear satellite sequences for nearly 1,110 wild and domestic dromedaries, along with sequences from seven ancient samples from early on in the animal's domestication. Their results pointed to extensive gene flow between dromedary populations from most parts of the world, apart from isolated populations in East Africa and genetically distant dromedaries from the Arabian Peninsula. As reported by GenomeWeb, the results offer a peek at dromedary domestication patterns, including a brief period of gene flow between wild and domestic populations.