PhD Exit Seminar – Brandy Velten (Welch lab)

PhD Exit Seminar

Friday August 26^th, 11:10 am – Room SW 403, University of Toronto at Scarborough

Brandy Velten (Welch lab)

“Comparative Identification and Characterization of Myosin Heavy Chain Isoforms in Avian Skeletal Muscle“

Abstract

Organisms require muscles capable of meeting the functional demands of locomotion. Many of the contractile properties of muscle are tightly correlated to the expression of specific myosin heavy chain (MHC) isoforms. While the identification and characteristics of mammalian MHC isoforms have been well documented, comparatively little is known about avian MHC expression. The diversity of locomotor styles and life histories observed in birds suggests that the locomotor muscles of these species must operate over a wide range of contractile conditions that may be achieved, in part, by the differential expression of MHC isoforms. Specifically, it was hypothesized that, due to their very rapid wingbeat frequencies, the MHC expression of hummingbird flight muscle would differ from that of larger-bodied species to enable rapid muscle shortening. Further, the unique contractile requirements associated with different locomotor and life history strategies across avian species would lead to varying MHC isoform expression both intra- and interspecifically. The aim of this thesis was to explore the MHC expression in avian skeletal muscle across species, muscle groups, and life history stages. While MHC expression appeared to vary across muscle groups tasked with performing different locomotor activities, the MHC expressed by the flight muscle initially appeared relatively conserved across species. However, analysis of pectoral MHC isoform(s) in a larger array of species revealed greater diversity, including the presence of several characteristically distinct avian isoforms. Analysis of characteristics that may influence MHC expression revealed that the migratory predisposition of a species corresponded with MHC expression in small-bodied passerine species. Examining the pectoral MHC expression of one migratory passerine species, the white-crowned sparrow (Zonotrichia leucophrys), across three life stages demonstrated that MHC expression of the flight muscle altered with the migratory status of the species. Thus, the avian MHC family of proteins appears to much more diverse than previously anticipated, with expression associated, in part, with meeting the mechanical demands associated with migration in some species. Continued research into the MHC expression and gene families of avian species will further our understanding of the evolutionary and functional implications of this observed diversity.