The Study About The Effects Of BAMBI In C2C12 Myogenic Differentiation

Bone morphogenic protein and activin membrane-bound inhibitor(BAMBI) is a transmembrane protein, which shares the extracellular domain with transforming growth factor-β(TGF-β) family type I receptor while lacking an intracellular kinase domain. BAMBI was regarded as an essential regulator for cell proliferation, migration and differentiation via represseing transforming growth factor-β(TGF-β) or enhanceing Wnt/β-catenin signaling in various cell types. Wnt/β-catenin signaling was also known as canonical Wnt signaling. The conjunction of Wnt ligands, Fzd, and LRP5/6 leads to the inactivation of destruction complex. Subsequently, β-catenin accumulates in cytoplasm and translocates into nucleus. BAMBI facilitates the interaction between Frizzled5, LRP6, and Dishevelled2, thus promoting canonical Wnt activity.Canonical Wnt signaling plays an essential role during embryonic muscle development, adult muscle regeneration, as well as the proliferation and differentiation of myogenic cell lines in vitro. Given the relationship between BAMBI and Wnt/β-catenin, we proposed that BAMBI might also regulate C2C12 differentiation through Wnt/β-catenin. In our studies, we measured the expression profile of BAMBI during C2C12 myogenic differentiation. Subsequently, we detected the influence of BAMBI knockdown on C2C12 and Wnt/β-catenin signaling. Lastly, we activated Wnt/β-catenin signaling using Li Cl to further test whether BAMBI affected myogenic differentiation through Wnt/β-catenin signaling. The main results are as follows: 1. BAMBI m RNA expression increased by 3-fold on Day 1 of myogenesis compared with1. BAMBI mRNA expression increased by 3-fold on Day 1 of myogenesis compared with undifferentiated condition(0 day), and then its expression gradually declined in the following days. 2. Knockdown of BAMBI inhibited myogenic differentiation. BAMBI si RNA reduced the expression levels of Myo D, Myo G and My HC. Meanwhile, the population of myotubes, differentiation index and fusion index were also decreased. 3. Knockdown of BAMBI inhibited Wnt/β-catenin activity. BAMBI si RNA reduced the Axin2 transcription and the nuclear translocation of β-catenin. 4. Li Cl rescued the influence of BAMBI interference on Wnt/β-catenin signaling and C2C12 differentiation. In the presence of Li Cl, BAMBI si RNA did not significantly reduce Axin2transcription, nuclear translocation of β-catenin, the expression of myogenic markers, the population of myotubes, differentiation index and fusion index.Altogether, BAMBI is an essential and positive regulator of C2C12 differentiation, and Wnt/β-catenin signaling mediates its role during myogenesis.