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This Week in PNAS: Oct 1, 2013

The evolution of haloarchaea in at least one super salty Antarctic lake has been helped along by rampant gene swapping between species from the same and different genera, according to a study in the early, online edition of the Proceedings of the National Academy of Sciences. The University of New South Wales' Ricardo Cavicchioli and colleagues from Australia and the US performed metagenomic- and 16S ribosomal RNA sequencing on samples collected from different depths in Antarctica's Deep Lake. Together phylogenetic and other assessments of that data, the study authors' analysis of four haloarchea isolates in the samples prompted them to conclude that the Deep Lake ecosystem "sustains a high level of inter-genera gene exchange while selecting for ecotypes that maintain sympatric speciation."

Researchers from the US and Switzerland describe various genetic loci that have contributed to convergent feeding postures in different populations of the Mexican cavefish Astyanax mexicanus. Along with assays designed to determine cavefish angles during feeding, the team turned to quantitative trait loci mapping and comparative genomics to look for genetic factors influencing these postures in three independent cavefish populations, which tend to approach food differently than fish that feed at the surface of a river. Two of the populations had developed comparable feeding postures with the help of different genetic loci, the study's authors say, suggesting "independently evolved populations of cavefish can evolve the same behavioral traits to adapt to similar environmental changes by modifying different sets of genes."

A University of Texas Health Science Center and Baylor College of Medicine team consider the clinical applicability of sequencing for another PNAS study. By doing exome sequencing, collecting medical histories and family information for 81 volunteers, and applying a bioinformatics analysis, the researchers detected alterations that appear to explain 24 individuals' medical conditions. Together with family history profiles, the study also turned up variants linked to half a dozen inherited conditions. "Our report demonstrates that when genome results are carefully interpreted and integrated with an individual's medical records and pedigree data, [next-generation sequencing] is a valuable diagnostic tool for genetic disease risk," authors of the study conclude.