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This Week in Cell: Feb 7, 2018

Researchers from the Chinese Academy of Sciences report on cynomolgus macaque (Macaca fascicularis) monkeys born to surrogate mothers after somatic cell nuclear transfer (SCNT) cloning. When the adult monkey cumulus cells were used as the DNA source for SCNT, the team achieved 22 pregnancies across 42 surrogate monkeys, though the two cloned monkey babies died of respiratory failure within three hours or 30 hours of birth. On the other hand, the two cynomolgus macaque clones produced with SCNT from fetal fibroblast cells appeared to be healthy and reportedly survived to the time of manuscript submission. "In both cases, genetic analyses confirmed that the nuclear DNA and mitochondria DNA of the monkey offspring originated from the nucleus donor cell and the oocyte donor monkey, respectively," the authors write, noting that they saw a boosts in cloned blastocyst development and pregnancy rates after doing epigenetic modulation at the one-cell stage. The Scan has more on this here.

A team from Japan and the UK takes a look at DNA-DNA interactions mediated by the cohesin complex during DNA replication in dividing fission yeast cells. Using a purified fission yeast cohesin complex assay and other approaches, the researchers retraced cohesin ring DNA binding and capture of a second single-stranded DNA, which appeared to rely on ATP hydrolysis. "Once [a] second ssDNA capture is followed by DNA synthesis, cohesin stably and topologically entraps two [double-stranded DNAs]," they say. "These results provide a molecular model of how cohesin engages in sister chromatid cohesion and maybe other chromosomal interactions."

Investigators from Stanford University present a high-resolution causal variant map that they generated in the yeast model organism Saccharomyces cerevisiae using inbred strain crosses and a computational model for more accurately narrowing in on individual variants from linkage and expression quantitative trait locus data. After spelling out the theoretical framework for this approach, the team applied it to S. cerevisiae, mapping 370 causal variants that appeared to mediate azole antifungal drug resistance and/or dozens of other quantitative traits. "We found that numerous missense, synonymous, and cis-regulatory mutations collectively gave rise to phenotypic diversity," the authors write, adding that "most traits we examined were genetically complex and were driven by both coding and non-coding variants."