Meeting Abstract

59.6  Friday, Jan. 6  Vertical jumping among mdm mouse genotypes TAYLOR, KR*; PACE, CM; MORTIMER, SA; NISHIKAWA, KC; Northern Arizona University; Northern Arizona University; Northern Arizona University; Northern Arizona University kt375@nau.edu

Jumping is a ballistic locomotor behavior that can help elucidate how muscles work. During jumping, elastic components in the limbs store and recover energy to increase jump height. The protein titin contributes to the elastic properties of muscle. Mdm mice have a deletion in the N2A region of titin and exhibit different in vitro muscle properties compared to wildtype mice. Studying vertical jumping in the mdm genotypes is an interesting biomechanical test of whether variation in titin affects locomotion. The goal of this project was to determine whether mdm genotypes differ in vertical jumping ability. Each genotype was filmed jumping using a high-speed imaging system. Mice were age matched; however, wildtype and heterozygous mice are larger than mutants, so data were examined both in absolute terms and relative to body mass. There was no difference among the genotypes in take-off time. Jumps by mutant mice were shorter, slower, and produced less force than the other genotypes. However, when data were scaled to account for differences in body mass, the average jump velocity and height of the mutants were not different from the other genotypes. The lack of variation between genotypes when scaled for mass is surprising given that previous research found differences in walking among all genotypes. Lever experiments with mdm mutant and wildtype muscles have shown that mutant muscles are stiffer than wildtype muscles when passive but more compliant when active. Perhaps the increased passive stiffness is in some way compensating for the increased active compliance in jumping but not in walking. By studying whole animal locomotion in addition to mechanical studies of mdm muscle, we will broaden our understanding of how titin contributes to muscle function. Supported by NSF IOS-1025806.