Sex-Specific Differential Gene Expression during Muscle Development in the Turkey

Turkey muscle development requires expression and regulation of myogenic regulatory factors, cell death mediators, and fiber and ECM proteins, among other factors. Details of this cascade have aided in the selection for fast-growth characteristics resulting in today’s heavily muscled commercial turkey, where males are more muscled than females. Differential expression of muscle-related genes was previously investigated in experimental lines selected for breast muscle growth at Ohio State University.  In comparison to genetically similar random-bred controls, phenotypic sex differences were evident. However, sex-specific differential gene expression during muscle development has not been thoroughly investigated.  Myogenin, MyoD, Death-associated protein, Versican, and Matrix Gla protein have known roles in muscle development and were differentially expressed between the OSU experimental lines. We hypothesized that genetically unrelated commercial turkeys selected for similar growth characteristics would show differential gene expression in these same genes.  To test this hypothesis, skeletal muscle was collected at day of hatch and weekly until 4 weeks of age from male and female birds obtained from a commercial breeding company.  Gene transcripts were evaluated using quantitative real-time PCR (qRT-PCR). Results show an overall trend of decreasing expression in the test genes during post-hatch development (except MYOG in males) reflecting the shift from hyperplasia and hypertrophy to skeletal muscle maintenance as the bird ages. While myogenic commitment between sexes did not differ, the myotubular stage of muscle development was prolonged in males as compared to females.