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This Week in PNAS: Feb 26, 2019

Researchers from the University of Missouri and other centers in the US and UK present a model for early-onset preeclampsia (EOPE) based on dozens of independent, induced pluripotent stem cells produced with umbilical cord cells from women with or without the pregnancy condition. With these induced pluripotent stem cells, the team went on to generate placental trophoblast cells that were subsequently profiled by marker gene analyses, RNA sequencing, and invasion assays under distinct growth conditions and oxygen contents. "Under low [oxygen], both sets of cells behaved similarly, but, under the more stressful [20 percent oxygen] conditions, the invasiveness of EOPE trophoblast was markedly reduced," the authors say, noting the gene expression data point to invasion dysregulation in the trophoblast under high oxygen conditions. 

A team from the University of Toronto and the Whitehead Institute for Biomedical Research explore the genetic modifiers that distinguish Saccharomyces cerevisiae from distinct genetic backgrounds, comparing two budding yeast lab strains subjected to systematic gene deletions. With hybrid crosses, whole-genome sequencing, and other approaches, the researchers identified non-chromosomal elements, single-modifier loci, and complex modifiers contributing to conditional essentiality in the each of the strains. From there, the authors focused on modifiers influencing cysteine biosynthetic pathway essentiality in natural yeast isolates, uncovering independent modifiers involving the OPT1 and MET1 genes. "[W]hile conditional gene essentiality is usually driven by genetic interactions associated with complex modifier architectures," they write, "our analysis also highlights the role of functionally related, genetically independent, and rare variants."

Members of an international team led by investigators at the University of Sheffield describe lateral gene transfer events, and their effects, in grasses. After putting together a chromosome-level genome assembly for the grass species Alloteropsis semialata, the researchers set it alongside genome sequences for 146 more grass species, uncovering dozens of previously unappreciated lateral gene transfer events in A. semialata. Their analyses hinted that at least nine donor species contributed to the two known and 57 new lateral gene transfer events, while nearly two dozen events involved the transfer of large gene fragments. "The majority of the 59 [lateral gene transfers] in A. semialata are expressed, and we show that they have added functions to the recipient genomes," the authors report, noting that still more lateral gene transfer events turned up in five of the other grass species considered.