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This Week in PNAS: Jul 31, 2018

A University of Utah-led team characterizes a muscle-specific histone methyltransferase called Smyd1 in the adult mouse heart. Using metabolomic, proteomic, targeted gene expression profiling, mitochondrial assay, and other approaches in cultured heart muscle cells and mouse models missing cardiac forms of Smyd1, the researchers uncovered apparent connections between Smyd1 histone methyltransferase function and heart energy metabolism, via regulation of oxidative phosphorylation proteins such as PGC-1-apha in the mitochondria. "Overall," the study's authors say, "these results provide a heretofore unrecognized function for Smyd1 as a potent positive regulator of mitochondrial metabolism in the heart."

Researchers from Italy and Japan explore the effects of helicase enzyme-coding mutations previously implicated in a developmental disorder known as Warsaw breakage syndrome — a condition with genome instability features resembling those in Fanconi anemia. After producing avian cell lines missing the DDX11 helicase involved in Warsaw breakage syndrome, the team traced cell survival, genome stability, and DNA interstrand crosslink repair patterns. From these and other experiments, the authors conclude that "DDX11 functions as backup to the [Fanconi anemia] pathway and facilitates, jointly with the checkpoint clamp 9-1-1, a homologous recombination pathway of DNA bulky lesion repair that does not affect replication fork speed and stalled fork stability."

A team from Denmark and Norway explore the history of acid-sensing ion channels (ASICs) over evolutionary time using genetic, phylogenetic, and electrophysiological recordings in acorn worms, starfish, sea urchins, lancelets, and tunicates. The researchers note that these ion channels, involved in the function of neurons and other components of the vertebrate nervous system, appear to show conservation across deuterostome animals. And that, in turn, hints that ASICs may go back some 600 million years or more, arising since the split between protostome and deuterostome animals. "Our results show that ASICs evolved much earlier than previously thought, suggest that proton-gated current may contribute to neuronal signaling throughout deuterostome animals, and point toward a mechanism of proton sensing involving several parts of the channel," they write.