title: The effects of a skeletal muscle titin mutation on walking in mice.
abstract: Titin contributes to sarcomere assembly, muscle signaling, and mechanical properties of muscle. The mdm mouse exhibits a small deletion in the titin gene resulting in dystrophic mutants and phenotypically normal heterozygotes. We examined the effects of this mutation on locomotion to assess how, and if, changes to muscle phenotype explain observed locomotor differences. Mutant mice are much smaller in size than their siblings and gait abnormalities may be driven by differences in limb proportions and/or by changes to muscle phenotype caused by the titin mutation. We quantified differences in walking gait among mdm genotypes and also determined whether genotypes vary in limb morphometrics. Mice were filmed walking, and kinematic and morphological variables were measured. Mutant mice had a smaller range of motion at the ankle, shorter stride lengths, and shorter stance duration, but walked at the same relative speeds as the other genotypes. Although phenotypically similar to wildtype mice, heterozygous mice frequently exhibited intermediate gait mechanics. Morphological differences among genotypes in hindlimb proportions were small and do not explain the locomotor differences. We suggest that differences in locomotion among mdm genotypes are due to changes in muscle phenotype caused by the titin mutation.
authors.affiliation: Department of Biological and Environmental Sciences, Le Moyne College, 1419 Salt Springs Road, Syracuse, NY, 13214, USA. pacecm@lemoyne.edu.
authors.forename: Cinnamon M
authors.identifier: http://orcid.org/0000-0002-5741-0081
authors.initials: CM
authors.lastname: Pace
authors.affiliation: Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, USA.
authors.forename: Sarah
authors.initials: S
authors.lastname: Mortimer
authors.affiliation: W.M. Keck Science Department, Claremont McKenna College, Claremont, CA, USA.|W.M. Keck Science Department, Pitzer College, Claremont, CA, USA.|W.M. Keck Science Department, Scripps College, Claremont, CA, USA.
authors.forename: Jenna A
authors.initials: JA
authors.lastname: Monroy
authors.affiliation: Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, USA.
authors.forename: Kiisa C
authors.initials: KC
authors.lastname: Nishikawa
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001696:Biomechanical Phenomena; D004195:Disease Models, Animal; D005121:Extremities / Q000473:pathology* / Q000503:physiopathology*; D005260:Female; D020233:Gait Disorders, Neurologic / Q000378:metabolism / Q000473:pathology; D008297:Male; D008822:Mice, Transgenic; D018482:Muscle, Skeletal / Q000378:metabolism*; D009154:Mutation; D010641:Phenotype; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D016059:Range of Motion, Articular / Q000502:physiology; D016138:Walking / Q000502:physiology*
chemical_list: D011494:Protein Kinases; C579730:titin protein, mouse
keywords: Locomotion; Mdm mouse; Morphometrics; Muscle; Titin