Meeting Abstract

P2.109  Thursday, Jan. 5  Implications of hind limb scaling across mouse mdm genotypes MORTIMER, SA*; PACE, CM; NISHIKAWA, KC; Northern Arizona University; Northern Arizona University; Northern Arizona University

The mouse mdm genotypes are an excellent model to study effects of variation in titin on locomotion. Previous work from our lab has shown that mdm genotypes vary in their kinematics. However, mutant mice are identified by their smaller size and it is possible that changes in titin also affect growth and development. If mutant hind limb segments are not proportioned the same as the other genotypes this needs to be accounted for when interpreting locomotor data. Therefore, the goal of this project was to determine if the mdm genotypes vary in the lengths of their limb elements and if that variation persists as they grow. We measured hind limb segments of each genotype ranging in age from 24 to 100 days old. For all genotypes, the longest limb segment is the calf, followed by the thigh, the metarasals, and the toes. Differences between wildtypes and heterozygotes are small, whereas mutants differed more. Across the entire age range, mutant body lengths and limb segments are smaller than the other genotypes. However, when body size is accounted for the hindlimbs of mutants are slightly longer than the other genotypes and their feet are larger. As there is no difference between heterozygous and wildtype limb segments, differences in locomotion may be driven by differences in titin function in muscle. While there are small differences in mutant leg segments, the fact that their legs are relatively longer while their stride length is relatively shorter, indicates that differences in titin function drive these locomotor differences, not differences in limb scaling. Given the utility of the mdm genotypes for elucidating the role of titin in muscle, understanding how the limb elements may differ is an important step to fully understanding the effect of titin on locomotion in these animals. Supported by NSF IOS-1025806.