Year

2022

Season

Summer

Paper Type

Master's Thesis

College

College of Arts and Sciences

Degree Name

Master of Science (MS)

Department

Biology

NACO controlled Corporate Body

University of North Florida. Department of Biology

First Advisor

Dr. David Waddell

Second Advisor

Dr. Frank Smith

Third Advisor

Dr. John Hatle

Abstract

Skeletal muscle atrophy is defined as a decrease in muscle size and occurs due to disparate physiological conditions, including aging, immobilization, and corticosteroid exposure. TSSK6 activating co-chaperone (TSACC) was identified as a gene that is significantly upregulated in skeletal muscle in response to denervation. To confirm Tsacc expression in skeletal muscle, the Tsacc cDNA was cloned from cultured myoblast cells leading to the discovery of a novel alternative splice-variant that is 49 amino acids shorter than the known full-length transcript. Quantitative PCR (qPCR) confirmed that Tsacc is expressed in skeletal muscle with expression increasing as muscle cells undergo differentiation. Characterization of Tsacc transcriptional activity revealed that Tsacc gene activity is modulated by myogenic regulatory factors (MRFs) and is significantly induced by MyoD. Moreover, sub-cellular localization was assessed by confocal microscopy, which showed that the two Tsacc proteins produced by the two alternatively spliced transcripts had distinct localization patterns. Tsacc-FL localized exclusively to the cytoplasm of muscle cells while Tsacc-novel localized diffusely within the cell, appearing in both the nucleus and cytoplasm of muscle cells. Finally, Western blot analysis revealed that ectopic expression of the full-length Tsacc transcript in C2C12 resulted in significant inhibition of conical markers of muscle differentiation, including MyHC and myogenin while the novel Tsacc transcript did not. The impact of Tsacc on the AKT signaling pathway, which is known to participate in the regulation of muscle size, was also assessed. Overexpression of either the full-length or novel Tsacc transcript was found to modulate the AKT signaling pathway in cultured muscle cells. Understanding the role of Tsacc will further our understanding of the molecular and genetic mechanisms of the muscle wasting and potentially provide new therapeutic targets for mitigating the negative outcomes associated with muscle atrophy.

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