In the PNAS Early Edition this week, researchers at the J. Craig Venter Institute and their colleagues report the genome sequences of Pediculus humanus humanus — the human body louse — and its primary bacterial endosymbiont, Candidatus Riesia pediculicola, which have implications for the study of human epidemic typhus, relapsing fever, and trench fever. The body louse, the authors write, "has the smallest known insect genome, spanning 108 Mb," and, when "compared with other insect genomes, the body louse genome contains significantly fewer genes associated with environmental sensing and response…" The researchers suggest that their study "offers unique information and tools to use in advancing understanding of coevolution among vectors, symbionts, and pathogens."
In another Early Edition article, an international research team reports that the PI3K-related kinase "Smg1 is required for embryogenesis and regulates diverse genes via alternative splicing coupled to nonsense-mediated mRNA decay." Specifically, using a gene-trap model of Smg1 deficiency, the team was able to show that the kinase is "essential for mouse embryogenesis, such that Smg1 loss is lethal at embryonic day 8.5." Using RNA-seq in Smg1-deficient cells, the researchers found that "Smg1 depletion led to pronounced accumulation of PTC-containing splice variant transcripts from approximately 9 percent of genes predicted to contain AS [alternative splicing] events capable of eliciting NMD [nonsense-mediated mRNA decay].
A collaborative effort among researchers at the Ohio State University School of Medicine and their colleagues at the University of California, San Diego, models B-cell chronic lymphocytic leukemia in a miR-29 expression-targeted mouse in PNAS this week. In creating Eμ-miR-29 transgenic mice overexpressing miR-29 in mouse B cells, the team found that, "on average, 50 percent of B cells in these transgenic mice were CD5 positive." The authors write that their data suggest that "dysregulation of miR-29 can contribute to the pathogenesis of indolent B-CLL."
Also in PNAS this week, researchers in Israel show that transcriptome diversity in primates is shaped by adenosine-to-inosine RNA editing. By sequencing the transcribed Alu sequences in humans, chimpanzees, and rhesus monkeys, the team found that, in general, "the editing level in the transcripts analyzed is higher in human brain compared with nonhuman primates, even where the genomic Alu structure is unmodified," and suggest that "the enhanced editing level in the human brain and the association with neuronal functions both hint at the possible contribution of A-to-I editing to the development of higher brain function."