In a paper published online in advance in Science this week, investigators at the University of Pennsylvania School of Medicine and the University of North Carolina School of Medicine report widespread RNA-DNA differences in the human transcriptome and suggest that these "provide a yet-unexplored aspect of genome variation." By comparing human B cell RNA sequences from 27 individuals to their corresponding DNA sequences, the Penn-UNC team found "more than 10,000 exonic sites where the RNA sequences do not match that of the DNA," and further, that these differences are non-random "as many sites were found in multiple individuals and in different cell types, including primary skin cells and brain tissues."
Jeffrey Gordon and his colleagues at the Washington University School of Medicine in St. Louis report in a Science advance online publication on a model community of 10 sequenced human gut bacteria into gnotobiotic mice. By measuring the effects of four randomized experimental dietary perturbations, Gordon et al. were able to generate "a statistical model that predicted over 60 percent of the variation in species abundance evoked by diet perturbations, and were able to identify which factors in the diet best explained changes seen for each community member."
In this week's issue, another team led by researchers at the University of Pennsylvania School of Medicine presents evidence to suggest "a functional prepattern of chromatin states within multipotent [mouse] progenitor cells." More specifically, in isolated murine embryonic endoderm cells, the researchers found histone modifications that are activated upon liver or pancreas fate choices.
Researchers at Pennsylvania State University and Germany's Universität München describe "a packing mechanism for nucleosome organization reconstituted across a eukaryotic genome" in this week's Science. The team says that adenosine triphosphate-dependent trans-acting factors are behind the "biochemical reconstitution of proper nucleosome positioning, spacing, and occupancy levels across the 5' ends of most yeast," adding that "these transcription-independent activities override DNA-intrinsic positioning."