Meeting Abstract
Tetratricopeptide repeat domain 39c (Ttc39c) was identified as a novel gene that is differentially regulated under conditions of neurogenic skeletal muscle atrophy in wild-type mice compared to Muscle-specific RING Finger 1 (MuRF1) knockout mice. MuRF1 is a ubiquitin E3 ligase that has previously been shown to be an important mediator of muscle wasting, however recent evidence suggests that MuRF1 may also function as a regulator of atrophy-induced gene expression. The transcriptional regulation of Ttc39c was examined by cloning the promoter region of this gene and fusing it to the secreted alkaline phosphatase (SEAP) reporter gene. This reporter construct was then transfected into muscle cells along with an expression plasmid for MuRF1. MuRF1 overexpression repressed Ttc39c reporter activity, while overexpression of a MuRF1 RING domain mutant failed to repress the Ttc39c reporter. Furthermore, overexpression of myogenin, which is a myogenic regulatory factor (MRF) that regulates the expression of muscle-specific genes by binding to elements called E-boxes, also repressed Ttc39c reporter gene activity. A conserved E-box element in the Ttc39c proximal promoter was identified, mutated and analyzed for its role in the regulation of Ttc39c expression. The mutation of the conserved E-box rendered the Ttc39c reporter gene inactive, demonstrating that the element is necessary for Ttc39c expression. The identification of Ttc39c as a novel gene that is activated under neurogenic atrophy conditions and the characterization of how this gene is transcriptionally regulated helps improve our understanding of the molecular genetic events that lead to skeletal muscle atrophy.
