42.2 Saturday, Jan. 5 The effects of a titin mutation on tremor frequency during shivering thermogenesis TAYLOR, KR*; NISHIKAWA, KC; Northern Arizona University; Northern Arizona University email@example.com
Muscular springs, such as titin, play an important role in determining muscle properties. The muscular dystrophy with myositis (mdm) mouse model is characterized by a deletion in the N2A region of titin. Previous work suggests that muscles from mdm mutants are stiffer when passive and more compliant when activated than wild type muscles. Shivering frequency is an ideal way to measure the in vivo consequences of muscle stiffness because frequency of tremor (f) should be directly proportional to (k/m)1/2 where k is stiffness and m is body mass. Because mutants have more compliant active muscles (i.e., decreased k), we expected that mutant mice would exhibit lower frequency tremors during shivering than predicted based on body mass. Further, we predicted that wild type and heterozygous mice would exhibit tremor frequencies expected based on body mass. Shivering was elicited by reducing ambient temperature, and tremor frequency was measured using an accelerometer attached dorsally to the trunk. The predicted tremor frequencies and the observed frequencies were not significantly different for wild type (expected: 41.5 Hz +/- 0.5 Hz; observed: 40.5 Hz +/- 3.5 Hz) and heterozygous mice (expected: 40.8 Hz +/- 0.8 Hz; observed: 39.5 Hz +/- 3.0 Hz). However, the observed tremor frequency for mutant mice (19.2 Hz +/- 4.1 Hz) was significantly lower than predicted by body mass (50.5 Hz +/- 0.7 Hz). These results support the hypothesis that the mdm mutation results in reduced active muscle stiffness in vivo. Thus, the results of this study demonstrate the important role that muscle stiffness, provided by titin, has in setting shivering frequency. Supported by NSF IOS-1025806.