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This Week in PNAS: Mar 27, 2013

In the early, online version of the Proceedings of the National Academy of Sciences, an international team led by investigators at Pennsylvania State University describes how it used genome sequencing to explore population patterns for the aye-aye — a nocturnal lemur species — in Madagascar. Using whole-genome sequence data on a dozen aye-ayes from the northern, western, or eastern parts of Madagascar, the researchers saw signs of genetic differentiation between aye-aye populations. That differentiation was particularly pronounced for aye-ayes from Madagascar's north, they report, pointing ongoing gene flow barriers between this lemur population and those found in other parts of the country.

Researchers from the University of California, Davis, and the University of British Columbia take a look at DNA methylation profiles in the human placenta for another PNAS study. The group performed MethylC-sequencing on DNA from full-term placental tissue, uncovering evidence of partially methylated domains over more than one-third of the genome. So far, such partially methylated domains have mainly been found in cancer samples or cell lines, the study authors say. But the new study suggests that these partially methylated epigenetic marks are stable in the placental genome over gestation, apparently contributing to gene regulation.

Southern European cattle introduced to the New World by Spanish settlers in the late 1400s primarily belonged to the so-called taurine lineage, but likely carried some genes from indicine cattle as well, according to a genomics-based study by researchers at the University of Texas at Austin and the University of Missouri. The team used new and existing genotyping data on almost 1,500 cattle — representing dozens of New World breeds as well as animals from Europe, Africa, and Asia — to assess ancestry patterns and selection histories of New World cattle. The analysis uncovered signs of previously unappreciated introgression from African cattle into the ancestors of Texas Longhorns and other present-day New World breeds, for example, as well as clues to the role that natural selection may have played in shaping New World cattle traits.