Meeting Abstract
67.3 Sunday, Jan. 6 Myostatin down-regulation in pectoralis muscle is associated with winter acclimatization in house sparrows Passer domesticus SWANSON, David L*; SABIRZANOV, Boris; CLARK, Timothy G; University of South Dakota ; University of South Dakota ; University of South Dakota david.swanson@usd.edu
Winter acclimatization in small birds overwintering in cold climates is associated with improved cold tolerance and elevated summit metabolic rates (Msum = maximum cold-induced metabolic rates) compared to summer birds. Accompanying the elevated Msum is an increase in pectoralis muscle mass. Myostatin is a potent autocrine/paracrine inhibitor of skeletal muscle growth in mammals and appears to function similarly in birds. As a first step toward examining a potential role for myostatin in regulating seasonal phenotypic flexibility in muscle mass and summit metabolic rates in small birds, we measured cold tolerance, Msum and gene expression of myostatin and its potential metalloproteinase activators, TLL-1 and TLL-2, in summer and winter house sparrows (Passer domesticus), a species showing winter increases in pectoralis muscle mass, from southeastern South Dakota. Msum increased significantly (11%) in winter relative to summer sparrows and this was associated with improved cold tolerance. Gene expression of myostatin decreased significantly in winter, with summer values exceeding winter values by 1.52-fold. Moreover, gene expression of TLL-1 was also significantly reduced in winter, with summer values exceeding winter values by 1.55-fold, whereas TLL-2 values were seasonally similar. These data are consistent with the hypothesis that the winter increase in pectoralis muscle mass in house sparrows, which is associated with elevated Msum and cold tolerance, is mediated by reduced levels of myostatin and its activator TLL-1 and suggest the possibility that myostatin might be a common mediator of phenotypic flexibility of muscle mass in birds.
