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PNAS Studies Cover ASD Gene Splicing, Nitrogen-Fixing Microbes, More

A Duke University-led team characterizes an autism spectrum disorder-associated, alternatively spliced version of the ANK2 gene, which produces a so-called giant ankyrin-B (ankB). Using CRISPR-Cas9 gene editing, the researchers produced mice with ASD-related splice changes affecting exon 37 of ANK2 before tracking mouse behavior and brain connectivity — analyses that highlighted enhanced neuronal axon branching and other brain connection changes in the giant ankB mice. From these and other results, the authors suggest that "gain of axon branching is a candidate cellular mechanism to explain aberrant structural connectivity and dominantly inherited behavior that are compatible with normal intelligence and potentially can contribute to ASD and other forms of neurodiversity."

Researchers from the US, Ethiopia, India, and elsewhere explore horizontal gene transfer in soil bacteria collected at sites around the world, focusing on chickpea crop symbionts capable of fixing nitrogen. The team generated more than 1,000 draft whole-genome sequences for Mesorhizobium bacteria populations collected from wild or cultivated chickpea-growing areas in North America, Australia, Morocco, Ethiopia, India, and Turkey, along with 14 high-quality Pacific Biosciences long read-based genomes. "Despite long-standing evolutionary divergence and geographic isolation," the authors write, "the diverse taxa observed to nodulate chickpea share a set of integrative conjugative elements that encode the major functions of the symbiosis." They note that these symbiotic elements are less closely tied to evolutionary distance between Mesorhizobium microbes than are features found in core bacterial genomes.

A team from Spain attempts to tease out potential relationships between telomere shortening and life span, using data from bird and mammal species ranging from griffin vultures to goats, mice, dolphins, reindeer, and Sumatran elephants. For their analyses, the researchers used high-throughput quantitative fluorescence in situ hybridization to measure telomere lengths in peripheral blood mononuclear cells from representatives of different ages from eight bird and mammal species. "We found that the telomere shortening rate, but not the initial telomere length alone, is a powerful predictor of species life span," they report, suggesting that telomere shortening and related DNA damage are, indeed, related to the life span of bird and mammal species.