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This Week in PNAS: Feb 7, 2017

A National Human Genome Research Institute-led team considers sequence variations in clonal fibroblast cell lines and induced pluripotent stem cells generated from skin fibroblast cultures. The researchers used a combination of exome sequencing and SNP genotyping to identify variant differences between fibroblast subclones and induced pluripotent stem cell lines compared to those found in the fibroblast populations used to produce them. For the most part, their results suggest that rare variants found in the cell line could be traced back to those parental populations, though a handful of de novo mutations turned up in both fibroblast cell lines and induced pluripotent stem cell lines.

Using gene expression clues, University of Washington researchers explore cell population patterns in induced pluripotent stem cells differentiating into cardiomyocyte cells specialized to function in the heart. The team tracked single-cell levels of 96 gene markers in nearly 2,000 cells over six days, as human induced pluripotent stem cells edged closer to a cardiomyocyte cell fate, uncovering a split between cell populations from distinct lineages involving different sets of transcription factors. "The analysis of cell populations undergoing a critical state transition … affords a tool to forecast cell fate outcomes," the authors write, "and can be used to optimize differentiation protocols to obtain desired cell populations."

A team from the University of North Carolina takes a look at DNA repair in Escherichia coli with the help of high-throughput sequencing. The researchers followed DNA repair after ultraviolet light exposure by sequencing short single-stranded DNA oligos produced during the repair process. Their results revealed a role for the Mfd translocase in transcription-coupled repair, while the UvrD helicase enzyme appeared to contribute to mechanical processes behind excision repair.