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This Week in PNAS: Jul 19, 2016

A study of phylogenetic and population genetic patterns in mouse lemurs gives insight into geographic change in Madagascar, according to a paper appearing in the Proceedings of the National Academy of Sciences this week. Madagascar is currently marked by rainforests in the east and dry deciduous forests, separated by a grassland savanna that's thought to have been created by human activity. The phylogenetic and population genetic patterns of five species of mouse lemurs from various sites in Madagascar suggest that the lemurs dispersed longitudinally across Madagascar during the Pleistocene. Further inter- and intraspecific genetic diversity analyses indicate that the natural environment of that current savanna was likely mosaic and formed a transitional zone, the researchers add.

A Florida State University and Baylor College of Medicine-led team reports that the deletion of the macrosatellite repeat DXZ4 in inactive X chromosomes affects higher-order genomic architecture. The researchers used 3D mapping, microscopy, and genome editing to study the inactive X chromosome. Through mapping they found that superloops tend to occur at the same time, and when DXZ4 is deleted, those superloops are disrupted, as are superdomain, and chromatin modifications are altered. This suggests "DXZ4 is essential for proper Xi packaging," the researchers write.

Researchers from Washington University School of Medicine linked a LOX gene variant with aortic rupture and aneurysm by sequencing the whole genomes of two affected first cousins. The researchers then used a CRISPR/Cas9 approach to introduce the mutation into a mouse model and found that mice heterogeneous for the mutation had disorganized aortic walls, while mice homozygous for the mutation died shortly after being born, suggesting that the LOX variant might be causal. GenomeWeb has more on this study, here.