All ETDs from UAB

Advisory Committee Chair

Peggy R Biga

Advisory Committee Members

Eugene S Berry

Julia H Bowsher

Mickie L Powell

Sarah Wagner

R Douglas Watson

Document Type

Dissertation

Date of Award

2014

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

During the course of vertebrate evolution, two major growth paradigms have appeared: determinate, one in which an animal's final size is largely governed by predisposed genetic potential; and indeterminate, a paradigm involving life-long, largely environmentally governed somatic growth. Of the tissues constituting an adult vertebrate, skeletal muscle comprises ≥60% of that organism's mass, making it an important factor in overall body growth. To better understand the process by which many teleost fishes grow throughout their natural lifespans, the clade Danioninae and the model rainbow trout (Oncorhynchus mykiss) were utilized in a comparative manner. Contrary to current hypotheses, fish with indeterminate growth possessed remarkably few myogenic precursor cells (MPCs) compared to their related determinate-like counterparts. However, upon stimulation with a growth promotants (GH), MPCs from indeterminate fishes appeared to expand by >300% (versus 100-200% in determinate danionins), suggesting a more `potent' proliferative nature of these cells. Upon in vitro culture and differentiation, MPCs from an indeterminate danionin, the giant danio (Devario aequipinnatus), express many of the factors known to govern myogenesis in mammals in a similar temporal manner except for two: paired-box factor-3 (Pax3) and myogenin. Similarly to Pax3 in the giant danio, rainbow trout express Pax7 transcripts even as cells appear to differentiate. At the epigenetic level, posttranslational modification of histone H3 correlate well with both Pax7 and myogenin expression, even in nascent myotubes. Using de novo myotubes derived from primary zebrafish myoblasts as a model, serum and amino acid withdrawal results in the transcription of genes associated with the autophagic and proteosomal responses. Of these, the Lamp1, Atg4b, p62/Sqstm1, and LC3b loci appear to be primed for autophagy, even in control cells. The studies contained herein are the first to use a truly comparative approach to gain key insights into the evolution of skeletal muscle in Vertebrata while guiding researchers and clinicians toward new treatments for myopathies and muscle wasting disorders and animal producers to more feed-efficient, faster growing livestock.

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