Meeting Abstract
P1.103 Saturday, Jan. 4 15:30 Interspecific and intermuscular differences in myosin heavy chain isoform expression: a case study using teleost jaw adductors STAAB, KL*; REISER, PJ; HERNANDEZ, LP; McDaniel College; Ohio State; George Washington kstaab@mcdaniel.edu
When asking questions about physiological properties of muscles, functional morphologists typically use electromyography or measurements of muscle mass or cross sectional area to derive meaningful metrics. Protein content of muscle is left for biochemists who often focus on model organisms, particularly mammals. Yet differences in sarcomeric protein isoforms could help explain functional diversity that characterizes teleost fishes. Specifically, disparities in myosin heavy chain (MyHC) isoforms largely determine contractile speed and force; thus differential expression of MyHCs underlies properties of whole muscles. We present a technique that has been ignored by functional morphologists with which large amounts of information can be obtained quickly without major investment in equipment. Using dot blots of extracted myosin and antibodies for different MyHC isoforms, we tested the hypothesis that divisions of jaw adductors in nine teleosts display patterns of MyHC expression correlated with functional diversity. The adductor mandibula is comprised of three divisions (A1, A2, & A3) and concomitant functions (A1-explosive upper jaw protrusion, A2-scraping and/or biting, A3-cyclic respiratory movements). This case study provides a framework for testing hypotheses of correlated MyHC expression and muscular function. We find that A1 shows a general correspondence between feeding mode and MyHC expression. While A3 contains the greatest proportion of slow MyHC, as expected given its function, there is greater diversity in predominant MyHC isoform among the examined species than predicted. We propose that this method can improve comparative studies of muscle function by addressing form-function from various levels of biological hierarchy.
