Muscle fibers are the main component of skeletal muscle and undergo maturation through the formation of myotubes.  During early development, a population of skeletal muscle satellite cells (SSCs) proliferate into myoblasts.  The myoblasts then undergo further differentiation and fusion events, leading to the development of myotubes.  However, the mechanisms involved in the transition from SSCs to myotube formation remain unclear.  In this study, we characterized changes in the proteomic and transcriptomic expression profiles of SSCs, myoblasts (differentiation for 2 d) and myotubes (differentiation for 10 d).  Proteomic analysis identified SLMAP and STOM as potentially associated with myotube formation.  In addition, some different changes in MyoD, MyoG, Myosin7 and Desmin occurred after silencing SLMAP and STOM, suggesting that they may affect changes in the myogenic marker.  GO analysis indicated that the differentiation and migration factors SVIL, ENSCHIG00000026624 (AQP1) and SERPINE1 enhanced the transition from SSCs to myoblasts, accompanied by changes in the apoptotic balance.  In the myoblast vs. myotube group, candidates related to cell adhesion and signal transduction were highly expressed in the myotubes.  Additionally, CCN2, TGFB1, MYL2 and MYL4 were identified as hub-candidates in this group.  These data enhance our existing understanding of myotube formation during early development and repair.

MicroRNA (miRNA) has vital regulatory effects on the proliferation, differentiation and secretion of ovarian granulosa cells, but the role of miR-99a-5p in goat ovarian granulosa cells (GCs) is unclear.  Both miR-99a-5p and Frizzled-5 (FZD5) were found to be expressed in GCs in goat ovaries via fluorescence in situ hybridization and immunohistochemistry, respectively, and FZD5 was verified (P<0.001) as a target gene of miR-99a-5p by double luciferase reporter gene experiments.  Furthermore, FZD5 mRNA and protein expression were both found to be regulated (P<0.05) by miR-99a-5p in GCs.  Moreover, the overexpression of miR-99a-5p or knockdown of FZD5 suppressed (P<0.05) estradiol and progesterone secretion from the GCs, as determined by ELISA.  In summary, miR-99a-5p inhibits target gene FZD5 expression and estradiol and progesterone synthesis in GCs.  Our study thus provides seminal data and new insights into the regulatory mechanisms of follicular development in the goat and other animals.