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This Week in Genome Biology: Feb 21, 2018

An international team led by investigators in Italy explores peopling patterns in the Sahara during a fertile period in the Holocene. Using targeted sequencing on 3.3 million bases of Y chromosome sequencing in more than 100 participants, the researchers identified almost 6,000 potential mutations, including 142 markers that appeared to be informative for population history. They used those markers to genotype another 8,000 or so African, Eurasian, or African-American individuals spanning 145 populations, retracing population expansion and dispersal in the relatively fertile "Green Sahara" based on haplogroup patterns. "Our data suggest that the favorable climatic conditions and the fertile environment established in the Sahara during the last African humid period promoted the occupation and dispersal of human groups," the authors write, "and contributed to the present distribution of Y lineages in northern and sub-Saharan Africa." 

Swiss and Australian investigators report on results from an epigenetic reprogramming analysis of the liverwort plant, Marchantia polymorpha. The team used whole-genome bisulfite sequencing to follow DNA methylation dynamics in eight male or female tissues collected across the liverwort's life cycle, identifying distinct epigenetic states at four main liverwort life cycle stages that pointed to at least two epigenetic reprogramming events in M. polymorpha. "We do not know whether resetting of DNA methylation is complete or if certain positions evade erasure," the authors noted. "An experiment including more generations and a sequencing depth saturation would be required to answer these questions."

Researchers from the Queen Mary University of London and elsewhere assess age-associated DNA methylation dynamics in half a dozen mammals: mice, dogs, naked mole rats, rhesus macaques, humpback whales, and humans. Focusing on age-associated differentially methylated positions (aDMPs) previously found in humans and mice, the team analyzed targeted bisulphite PCR and/or Illumina 450K array profiles for various tissues from the six mammalian species at hand. The authors identified inverse ties between aDMP methylation rate change and lifespan, including differences in aDMP dynamics in distinct dog breeds. "[W]e define the first dynamic molecular readout of lifespan differences among mammalian species," they write, "and propose that aDMPs will be an invaluable molecular tool for future evolutionary and mechanistic studies aimed at understanding the biological factors that determine lifespan in mammals."