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This Week in PNAS: Jul 21, 2015

In a study appearing online this week in the Proceedings of the National Academy of Sciences, researchers from the US and Brazil demonstrate the feasibility of finding cell-free DNA in the cerebrospinal fluid that stems from tumors in the brain or spinal cord. The team started by using targeted sequencing and/or exome sequencing to find cancer-specific mutations in tumor samples from 35 individuals with primary gliomas or medulloblastomas. In almost three-quarters of the cases, investigators identified the same mutations through PCR amplification of cerebrospinal fluid samples, though they didn't pick up any of this 'CSF-tDNA' in fluid samples from individuals whose tumors didn't neighbor the cerebrospinal fluid space. GenomeWeb has more on this study here.

A team from Germany, the US, and UK explore the consequences of tinkering with methylcytosine oxidizing enzymes in developing mouse embryos. Using RNA sequencing, the researchers tracked transcriptional patterns in two- and eight-cell mouse embryos missing the Tet1 and Tet3 enzymes. Without these enzymes, the embryos had altered epigenetic features, including lower-than-usual levels of 5-hydroxymethylcytosine, enhanced 5-methylcytosine levels, and variable gene expression, the study's authors note, arguing that "TET enzymes and DNA cytosine modifications could directly or indirectly modulate transcriptional noise."

Finally, a Harvard Medical School-led group searches for genetic factors influencing bodily features that make it possible for humans to cool off with sweat, a process known as evapotranspiration. In particular, the researchers searched for genes determining the density of eccrine sweat glands and hair follicles, using whole-genome quantitative trait locus mapping in mice falling at each end of the sweat gland- and hair follicle-density spectrum. Their analysis suggests expression of a transcription factor called En1 is key to regulating the relative densities of eccrine sweat glands and hair follicles in mice, perhaps offering evolutionary clues to sweat gland density and development in humans.