The researchers discovered that the genetic activity of mouse skeletal muscles is particularly intense during the first two weeks after birth; a number of genes alter the amount of proteins produced, while other genes go through alternative splicing and produce different proteins.

Among the genes going through alternative splicing, those involved in calcium-handling functions predominated. Calcium is very important for skeletal and heart muscle because the influx of calcium into the cell stimulates contraction and other functions.

First author Dr. Amy Brinegar, who was a graduate student in the Cooper lab while she was working on this project and recently graduated from the doctoral program in molecular and cellular biology at Baylor, selected three calcineurin A genes, which are involved in calcium-handling functions, and reversed their natural process of alternative splicing in adult mouse muscles. Then, Dr. George Rodney, associate professor of molecular physiology at Baylor, and a graduate student in his lab, James Loehr, who are co-authors on this paper, determined the effect of switching back alternative splicing on functions of isolated adult mouse skeletal muscle in the lab.

They discovered that muscles in which the adult forms of the calcineurin A genes had been switched back to the newborn forms showed a change in calcium flow and were less strong than muscles that retained the adult forms of calcineurin A.

We showed that just by changing three of about 11,000 genes that are estimated to be expressed in adult mouse muscle, we were able to change physiological parameters of those muscles, said Brinegar. This work supports the growing evidence in favor of a physiological role of alternative splicing.

Importantly, about 50 percent of the genes we discovered to undergo alternative splicing are conserved, meaning that the genes go through the same changes both in mice and humans, which opens the possibility of modeling human muscle disorders in the mouse, Cooper said.

Other contributors top this work include Zheng Xia and Wei Li, both from Baylor.

Financial support was provided by National Institutes of Health grants R01AR045653, R01HL045565, R01AR060733, T32 HL007676, R01HG007538, R01CA193466 and R01AR061370. Further support was provided by the Muscular Dystrophy Association grant RG4205.

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Change in protein production essential to muscle function - Baylor College of Medicine News (press release)