03/13/2025
By Irma Silva
Candidate: Nicholas LaFave
Date: Thursday, March 27, 2025
Time: 10 a.m. – 12 p.m.
Location: Olney 218
Committee members:
Jeffrey Moore (Advisor), Professor, Biological Sciences, UMass Lowell
Nicolai Konow, Associate Professor, Biological Sciences, UMass Lowell
Matthew Gage, Professor, Chemistry. UMass Lowell
Title: "Unraveling Myosin Isoform Complexity in Rodents: Insights from Injury Adaptation and Specialized Jaw Systems"
Abstract:
Skeletal muscle is a complex, hierarchical structure requiring research using a multiscale approach to understand the interplay of mechanisms at each scale. Muscle function at the finer scales relies on the interactions and properties of various sarcomeric proteins, including myosin, the motor protein responsible for hydrolyzing ATP and producing the force required for muscle contraction. Myosin exists as numerous different isoforms with various contractile properties, such as velocity of contraction and force production, which relate to the function of the muscle that it makes up. To further study the effects myosin isoform composition has on muscle, two projects focusing on skeletal muscle in rodents were completed, with one focusing on limb muscle and the other on jaw muscles. It has been shown that eccentric, or lengthening, muscle contractions create a protective effect against further injury, known as the SBE phenomenon, although the exact mechanism at which this occurs is not well understood. Therefore, it was hypothesized that SBE is mediated by a shift in myosin isoform composition. The first project tests this hypothesis by eccentrically stretching mouse tibialis anterior muscle and testing for changes in myosin isoform composition and in function. No significant changes in myosin isoform composition or in velocity of contraction were observed. In another skeletal muscle system, the jaw, there exists a unique myosin isoform, named masticatory myosin (MHC-M). MHC-M is found in vertebrate species that require a strong bite, including in some species of rodents. Previous literature has shown possible links between MHC-M expression and muscle function, diet and skull type in rodents but were limited in scope. Therefore, it was hypothesized that in rodent species that express MHC-M, only jaw-closing muscles express the isoform. The myosin isoform composition of the jaw muscles of six rodent species were observed and averaged, showing that MHC-M is expressed almost entirely in jaw-closing muscles exclusively, with one exception. Additionally, species within and across skull types, as well as species of different sizes, showed distinct myosin isoform diversity within the jaw muscles. The results of both projects demonstrate the complexity of myosin isoforms with respect to the function of the muscles they compose, as well as the necessity of interdisciplinary, multiscale research that this work is just one part of.