Regulation of skeletal muscle development requires many of the regulatory networks that are fundamental to developmental myogenesis. ErbB3 binding protein-1 (Ebp1) is involved in the control of myoblasts development in chicken. However, the expression and biological functions of Ebp1 in the progress of myogenesis are unclear. This study focused on determining the effect of Ebp1 on myogenic proliferation and differentiation using a primary myoblasts culture model. Ebp1 was found to upregulate in proliferating myoblasts and decrease at the early stage of myogenic differentiation. The level of endogenous Ebp1 increased from E9 to E20 chicken leg muscles. Knockdown of Ebp1 had no effect on myoblasts proliferation. However, myogenic differentiation into multinucleated myotubes was significantly reduced. The mRNA and protein expression of MRFs was decreased when Ebp1 was knocked down. Downregulation of Ebp1, accompanied by elevated levels of pSMAD2/3, suggests that Ebp1 is involved in regulating myogenic differentiation via SMAD2/3 inhibition. The phosphorylation of SMAD2/3 was activated and the expression of MYOD and MYOG was reduced in Ebp1 knockdown myoblasts, but addition of LY2109761 (an inhibitor specified to SMAD2/3) blocked these effects. Collectively, these results indicate that Ebp1 promotes myoblast differentiation by inhibition of SMAD2/3 signaling pathway during chicken myogenesis. These data provide new insights into the biological role of Ebp1 in embryonic chicken skeletal muscle development.

During embryonic development, IGF-1 fulfils crucial roles in skeletal myogenesis. However, the involvement of IGF-1-induced myoblast proliferation in muscle growth is still unclear. In the present study, we have characterised the role of IGF-1 in myoblast proliferation both in vitro and in vivo and have revealed novel details of how exogenous IGF-1 influences myogenic genes in chicken embryos. The results show that IGF-1 significantly induces the proliferation of cultured myoblasts in a dose-dependent manner. Additionally, the IGF-1 treatment significantly promoted myoblasts entering a new cell cycle and increasing the mRNA expression levels of cell cycle-dependent genes. However, these effects were inhibited by the PI3K inhibitor LY294002 and the Akt inhibitor KP372-1. These data indicated that the pro-proliferative effect of IGF-1 was mediated in response to the PI3K/Akt signalling pathway. Moreover, we also showed that exogenous IGF-1 stimulated myoblast proliferation in vivo. IGF-1 administration obviously promoted the incorporation of BrdU and remarkably increased the number of PAX7-positive cells in the skeletal muscle of chicken embryos. Administration of IGF-1 also significantly induced the upregulation of myogenic factors gene, the enhancement of c-Myc and the inhibition of myostatin (Mstn) expression. These findings demonstrate that IGF-1 has strong activity as a promoter of myoblast expansion and muscle fiber formation during early myogenesis. Therefore, this study offers insight into the mechanisms responsible for IGF-1-mediated stimulation of embryonic skeletal muscle development, which could have important implications for the improvement of chicken meat production.

The mature adipocyte dedifferentiation is able to provide homogeneous preadipocyees for researching adpocyte differentiation. In this study, mature adipocytes were isolated and cultured from adipose tissue, and then dedifferentiated to achieve preadipocytes. The subcutaneous adipose tissue from 3-day-old piglets(Sus scrofa) were digested by collagenase type Ⅱ, followed by centrifugation at different centrifugal force and then cultured by ceiling method. Morphological changes of adipocytes were observed under microscope, and the degree of adipogenesis and differentiation was assessed via oil red O staining. By inducing, adipose-derived progeny cells were redifferentiated into lipid-laden cells with accumulation of lipids. In terms of expression level, peroxisome proliferator-activated receptor-γ (PPARγ) and fatty acid binding protein 4 (FABP4) were detected by Real-time PCR. As we expected, the adipogenic markers, PPARγ and FABP4, increased along with the redifferentiation process. Particularly, a 2.8-fold increase of PPARγ expression, and a 62-fold of FABP4 were shown in the late phase of the redifferentiation process, demonstrating the significantly higher expression levels comparing with the unredifferentiated cells at 0 d(P0.05). Showing that the predipocytes obtained by dedifferentiation might effectively differentiate to mature adipocytes with adipogenic induction agent. In addition, our study optimized the mature adipocytes culture system as well. Using this system, mature adipocytes can revert into proliferative-competent progeny cells by inducing redifferentiate again into mature adipocytes, which contributes an in vitro model for adipocytes investigation.