In this week's PNAS Early Edition, researchers at Tufts University School of Medicine, along with their colleague at Harvard Medical School, show that "minimization of the Legionella pneumophila genome reveals chromosomal regions involved in host range expansion." By screening for genes necessary for optimal growth in nutrient-rich medium, the team found that the "L. pneumophila chromosome has a modular architecture consisting of several large genomic islands that are dispensable for growth in bacteriological culture," it says.
Elsewhere in the Early Edition, investigators at the University of Colorado, Denver, show that a transgenic mouse strain that generates the interleukin 37, or IL-37, shows reduced inflammation and an associated decreased leukocyte recruitment into the colonic lamina propria during experimental colitis. "Mechanistically, IL-37 originating from hematopoietic cells was sufficient to exert anti-inflammatory effects because WT mice reconstituted with hIL-37tg [human IL-37] bone marrow were protected from colitis," the authors write in PNAS, adding: "Thus, IL-37 emerges as key modulator of intestinal inflammation."
Using mRNA sequencing, researchers at the Yale University School of Medicine were able to define "five transcriptional programs that represent each transient embryonic zone and the progression between these zones" throughout the development and evolution of the cerebral cortex. In a PNAS paper published online in advance this week, the team says that those five programs "contain largely uncharacterized genes in addition to transcripts necessary for stem cell maintenance, neurogenesis, migration, and differentiation," and add that "intergenic transcriptionally active regions … possibly encode unique zone-specific transcripts." In its paper, the team also reports a high-resolution transcriptome map of transient zones in the murine embryonic forebrain.
Harvard University's Chris Organ et al. report their application of phylogenetic analyses to characterize rate shifts in feeding time throughout the evolution of the Homo genus. The researchers assessed "the inferred evolutionary consequences of food processing in the human lineage by applying a Bayesian phylogenetic outlier test to a comparative data set of feeding time in humans and nonhuman primates," finding that "modern humans spend an order of magnitude less time feeding than predicted by phylogeny and body mass — 4.7 percent versus [the] predicted 48 percent of daily activity." The team also discusses the phylogenetic consequences related to a reduction in molar size observed across species in the genus. "Together, our results indicate that the behaviorally driven adaptations of food processing — reduced feeding time and molar size — originated after the evolution of Homo but before or concurrent with the evolution of H. erectus," the authors write.