Peter J. Reiser, MS, PhD
We are exploring differences in muscle properties between species which are, in some cases, closely related phylogenetically and, in others, between species that are distantly related. The comparative approach is yielding new information on aspects of muscle physiology and contractile protein expression that are shared among a broad range of species, illustrating common, evolutionarily-conserved themes, while also highlighting striking differences between members of the same phylogenetic family, even differences between genera of the same family. We are also studying mammalian craniofacial muscles which have highly specialized motor functions, relative to functions of limb muscles that serve primarily locomotion. These functions include eye rotations around three independent axes by extraocular muscles, protection of the airway to prevent aspiration by intrinsic laryngeal muscles, and generation of bite forces by jaw-closing muscles. We are also combining out comparative interests by studying differences in craniofacial muscles between multiple mammalian species to determine how craniofacial muscle properties subserve species-specific motor functions. The research is focused on the roles of sarcomeric protein isoforms in regulating contractile properties of muscle. The approach is based primarily on analyses of contractile properties and protein composition of single, isolated muscle cells.
Recent discoveries in my laboratory are (1) the expression of masticatory myosin, an evolutionarily ancient protein, in jaw-closing muscles of several rodent species, (2) the expression of the embryonic/atrial isoform of myosin light chain 1 as a subunit of masticatory myosin in all species (reptilian, eutherian mammals, marsupials) in which the latter is expressed, and (3) a fundamental difference, between members of Carnivora and Rodentia that express masticatory myosin, in thin filament proteins of jaw-closing muscles that have pivotal roles in muscle activation by calcium and that might determine between carnivores and rodents.