Similar reductions in expression of proliferative genes are observed in skeletal muscle and organs with age

Abstract

Our objective was to observe skeletal muscle expression of 7 genes previously identified in the regulation of organ growth. With age, these genes involved in proliferation were down‐regulated. We hypothesized that these genes would be similarly down‐regulated with muscle growth, but expression would differ between sexes. C57BL/6J female and male mice were sacrificed at 0, 1, 3, 5, and 7 weeks of age. Hind limb muscles from 0 and 1 week old mice, and specific muscles (bicep femoris, gastrocnemius, tibialis anterior, and triceps brachii) from 3, 5, and 7 week old mice were collected along with hearts and livers. Expression of Ezh2, Gpc3, Mdk, Mest, Mycn, Peg3, and Plagl1 was determined by quantitative PCR and normalized to 18s rRNA. At 3 weeks of age, Gpc3, Mest, Peg3, and Plagl1 expression was reduced from newborn expression levels in all tissues (P<0.05 for age). Expression of Ezh2 and Mdk was reduced in heart and muscle at 3 weeks, but not in liver. Few differences in expression were observed between males and females; however, when males and females differed, expression was generally reduced in females. These differences may be related to females reaching mature size sooner than males. Overall, these data suggest that down‐regulation of these proliferative genes with age may coordinate the eventual decreased growth in both muscle and organs. This research was supported by the USDA/NIFA Multi‐State Project NC‐1184.