Meeting Abstract

P1.140  Saturday, Jan. 4 15:30  The Regulation of Myostatin by Cortisol in Three Closely Related Salmonids GALT, NJ*; FROEHLICH, JM; BIGA, PR; University of Alabama at Birmingham, Birmingham nicholasgalt@uab.edu

Glucocorticoids are strong positive regulators of myostatin (mstn) in mammals, and the glucocorticoid response elements (GREs) appear to be well conserved within the promoter of mstn in vertebrates, including many fishes. However, putative GREs have not been identified in the promoters of the three functional mstn genes (mstn-1a, -1b, and -2a) present in rainbow trout (Oncorhynchus mykiss). Interestingly, this is contrary to what has been observed in other salmonids, including Atlantic salmon and brook trout. We hypothesize that promoter region differentiation allows for greater diversity in local tissue control, and could explain stress tolerance differences observed across Salmonids. The goal of this study was to determine the effects of cortisol, the endogenous glucocorticoid in fishes, on mstn gene expression in rainbow trout and two close relatives, cutthroat trout (Oncorhynchus clarki) and Chinook salmon (Oncorhynchus tshawytscha). To this end, fish received a single intraperitoneal injection of either cortisol (50 ug/g, n=10), RU-486 (200 ug/g, n=10), both cortisol and RU-486 (n=10) or the vehicle (10 ul/g vegetable oil:shortening, n=10). Tissue samples were collected 48 hours following the injection and analyzed for myostatin mRNA expression by qPCR. Our results demonstrate that the regulation of mstn in these fishes, unlike mammals, is not highly regulated by glucocorticoids, but instead is extremely complex. Further research is needed to functionally characterize and annotate the mstn promoters in these and other fishes.