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This Week in Cell: Jun 4, 2014

A group from China and the US used a combination of sequencing strategies to look at maternally and paternally inherited DNA methylation patterns and reprogramming in developing mice. To do this, the researchers mapped both DNA methylation as well as the hydroxymethyl-, formyl-, and carboxyl-cytosine modifications formed as 5-methylcytosine is oxidized. Their single-base, allele-specific DNA methylation data in mouse reproductive cells, embryos, and primordial germ cells — together with oxidized cytosine maps in early mouse embryos — pointed to active demethylation at a slew of paternally methylated sites (and at least some maternally methylated sites) during development.

The helicase enzyme gene RECQL5 has a regulatory role in transcription elongation that seems to mute transcriptional stress-related genomic instability, according to a study by researchers from the UK and Germany. Through chromatin immunoprecipitation sequencing and other experiments, the researchers determined that the RECQL5 gene product, already known for its interactions with RNA polymerase II, acts as a genome stability-maintaining elongation factor.

An international team led by investigators in the US, Denmark, and China turned to population genomic approaches to explore polar bear evolution and adaptations. After sequencing and assembling a polar bear reference genome, the researchers re-sequenced 79 polar bears and 10 brown bears from various populations living in different parts of the world. The sequence data suggested that the polar and brown bear lineages split from one another between 343,000 and 479,000 years ago, while the investigators' search for signs of positive selection in the polar bear highlighted several genes homologous to human heart- and lipid-related genes.