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This Week in PNAS: Jan 5, 2016

Editor's Note: Some of the articles described below are not yet available at the PNAS site, but they are scheduled to be posted some time this week.

In the early, online edition of the Proceedings of the National Academy of Sciences, an Albert Einstein College of Medicine- and New York University-led team explores the roles the type VII secretion system ESX-3 plays in the tuberculosis-causing pathogen Mycobacterium tuberculosis using growth studies of the pathogen paired with genetic and proteomic approaches. Based on their in vitro and in vivo growth assays on mutant M. tuberculosis strains lacking ESX-3 component coding sequences and other genes, coupled with proteomic profiling of compounds secreted by such pathogens, the researchers found hints that ESX-3 is not only involved in iron acquisition, but also participates in M. tuberculosis pathogenesis through both iron-dependent and iron-independent processes.

Researchers from the US and Singapore consider the nature of genes that are enriched in expanded surfaces of the human brain's cortex in another study slated to appear in PNAS. With the help of information from the Allen Institute Human Transcriptional Atlas, existing data on the brain's lamina, functional connectivity magnetic resonance imaging experiments, and microarray-based gene expression data on six post-mortem brains, the team looked at the relationship between genes enriched in the upper cortical layers of the human brain and those involved in various cortical functions and networks. "The results suggest that molecular innovations of upper layer cortical architecture may be an important component in the evolution of long-range corticocortical projections in humans," the study's authors write.

Chinese Academy of Sciences researchers describe differences in expression of the microRNA miR-276 in social and solitary forms of the biologically synchronous migratory locust Locusta migratoria. Using high-throughput small RNA sequencing and other approaches, the team saw differences in miR-276 expression in the ovaries and eggs of the gregarious migratory locusts — those showing more synchronized sexual maturation, egg-hatching, and migration behaviors — compared to their so-called solitarious counterparts. Through a series of follow-up experiments, the investigators found that dialing down miR-276 levels in gregarious female locusts led to less synchronous hatching of their offspring, while enhanced activity of the miRNA in solitarious females had the opposite effect — patterns that appear to reflect miR-276's regulation of a transcription coactivator gene called brahma.