All ETDs from UAB

Advisory Committee Chair

Peggy R Biga

Advisory Committee Members

Mark Sheridan

Stephen McCormick

Thane Wibbels

Douglas Watson

Document Type

Dissertation

Date of Award

2014

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

The relationship between the muscle growth inhibitor, myostatin, and the stress response has been extensively studied in mammals, and myostatin is now known to partially mediate the degradative effects of stress in skeletal muscle. In fish, this relationship has not yet been clearly described. Herein, the effects of two stress mimetics, cortisol treatment and crowding, on myostatin-1a, -1b, and -2a expression in rainbow trout (Oncorhynchus mykiss), cutthroat trout (Oncorhynchus clarki), Chinook salmon (Oncorhynchus tshawytscha), brook trout (Salvelinus fontinalis), and Atlantic salmon (Salmo salar) are described. In study I, no clear effects on myostatin mRNA expression were detected in rainbow trout following cortisol treatment; however, myostatin-1b responded to cortisol in a dose-dependent manner in primary rainbow trout myoblasts. Study II was conducted to further investigate the effects of cortisol treatment on myostatin expression in Chinook salmon, cutthroat trout, brook trout, and Atlantic salmon. The resulting expression profiles were highly variable among species, and the myostatin paralogs were regulated in a fiber type-specific manner. Significant changes in myostatin expression were also detected in response to the vehicle treatment alone and the addition of cortisol generated both additive and inhibitor effects depending on the paralog. Overall, the species-specific effects suggest that the regulation of the myostatin paralogs by cortisol has diverged among these salmonids. The final study found further interspecies variation and muscle-type specific regulation in animals exposed to a 48 hr crowding stress. Interestingly, the Atlantic salmon myostatin paralogs were the most responsive to this treatment with all three paralogs being upregulated, whereas, no changes in expression were detected in rainbow trout. Overall, the treatment responses were not consistent between experiments, which suggests that different `types' of stressors differentially regulate myostatin expression. This dissertation demonstrates that the relationship between myostatin and the stress response is paralog dependent, highly species-specific, and may be more complex than in mammals. Collectively, these novel findings provide a foundation for further work characterizing the mechanisms regulating myostatin in salmonids and contribute important knowledge towards understanding the biology of myostatin in fishes.

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