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PNAS Papers on Siberian Dog Ancestry, Insect Reproduction, Hippocampal Neurogenesis

Researchers from the University of Copenhagen, the University of London, the Ludwig Maximilian University, and elsewhere retrace the ancestry of Siberian dogs over thousands of years, uncovering signs of admixture with European and Eurasian Steppe dogs apparently introduced through trade networks that connected parts of Siberia with Eurasia. Based on ancient genome sequences for 20 dogs in Siberia and the Eurasian Steppe, analyzed in combination with 29 additional ancient genomes and genomes for 120 modern canid representatives, the team estimates that the genetic homogeneity of Siberian dogs from around 7,000 to 9,500 years ago was followed by more recent admixture with dogs from the Eurasian Steppe and Europe. "The analysis of 49 ancient dog genomes reveals that the ancestry of Arctic Siberia dogs shifted over the last 2,000 years due to an influx of dogs from the Eurasian Steppe and Europe," the authors report. "Combined with genomic data from humans and archeological evidence, our results suggest that though the ancestry of the human populations in Arctic Siberia did not change over this period, people there participated in trade with distant communities that involved both dogs and material culture."

A team from China and Germany explores juvenile hormone contributions to insect reproduction in Drosophila fruit flies carrying mutant versions of the juvenile hormone receptor-coding genes Met and Gce. Using a series of phenotypic and expression analyses, the researchers saw signs that such mutations may prompt a buildup of shorter-than-usual mature eggs in the fruit fly ovary. On the other hand, typical juvenile hormone signaling appeared to prompt extracellular matrix (ECM) assembly in ovarian muscle and in adult fat bodies through the induction of laminin in ovarian muscle cells and a form of collagen in body fat cells from the adult body. "The ECM components are indispensable for ovarian muscle contraction that externally generates a mechanical force to prompt ovulation and maintain egg shape in Drosophila," the authors report.

Investigators in Taiwan and the US describe a role for follistatin (FST) in synaptic plasticity and leaning in the mouse hippocampus. With a combination of genetic mapping experiments, mouse knockout experiments, RNA sequencing profiles, and chromatin immunoprecipitation analyses, the team saw lower-than-usual spatial learning abilities, memory, long-term potentiation, and hippocampal neurogenesis in animals missing FST — effects that could be overcome by overexpression the gene and appeared to involve a target protein called Asic4. "Our study demonstrates the power of combining genetic mapping with functional work," the authors note, "and we provide insights into the role of FST in the hippocampus and its influence on learning."