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Background  Genes that decline in expression with age and are thought to coordinate growth cessation have been identified in various organs, but their expression in skeletal muscle is unknown. Therefore, our objective was to determine expression of these genes ( Ezh2 ,  Gpc3 ,  Mdk ,  Mest ,  Mycn ,  Peg3 , and  Plagl1 ) in skeletal muscle from birth to maturity. We hypothesized that expression of these genes would decline with age in skeletal muscle but differ between sexes and between wild type and myostatin null mice.    Results  Female and male wild type and myostatin null mice (C57BL/6J background) were sacrificed by carbon dioxide asphyxiation followed by decapitation at d -7, 0, 21, 42, and 70 days of age. Whole bodies at d -7, all muscles from both hind limbs at d 0, and bicep femoris muscle from d 21, 42 and 70 were collected. Gene expression was determined by quantitative real-time PCR. In general, expression of these growth-regulating genes was reduced at d 21 compared with day 0 and d -7. Expression of  Gpc3 ,  Mest , and  Peg3  was further reduced at d 42 and 70 compared with d 21, however the expression of  Mycn  increased from d 21 to d 42 and 70. Myostatin null mice, as expected, were heavier with increased biceps femoris weight at d 70. However, with respect to sex and genotype, there were few differences in expression. Expression of  Ezh2  was increased at d 70 and expression of  Mdk  was increased at d 21 in myostatin null mice compared with wild type, but no other genotype effects were present. Expression of  Mdk  was increased in females compared to males at d 70, but no other sex effects were present.    Conclusions  Overall, these data suggest the downregulation of these growth-regulating genes with age might play a role in the coordinated cessation of muscle growth similar to organ growth but likely have a limited role in the differences between sexes or genotypes.

Reductions in expression of growth regulating genes in skeletal muscle with age in wild type and myostatin null mice