Abstract
In the developing skeletal muscle, fusion of myoblasts and myotube formation is a process that involves Ca^2+^ influx through T‐type (Ca~V~3) channels. Treatment of myoblasts with transforming growth factor‐β1 (TGF‐β1) and bone morphogenetic protein‐2 (BMP‐2) decreases the number of Ca~V~3 channels in the plasma membrane and reduces myotube formation. In the current report, we examined whether the inhibitory actions of TGF‐β1 and BMP‐2 involve alterations in Ca~V~3 mRNA expression in the myoblast C2C12 cell line. Using RT‐PCR, we found that Ca~V~3.1 but not Ca~V~3.2 and Ca~V~3.3 transcripts are present in either undifferentiated or fusion competent C2C12 myoblasts. Semi‐quantitative analysis revealed a significant decrease of Ca~V~3.1 mRNA expression in cells treated with TGF‐β1 and BMP‐2. In contrast, patch‐clamp recordings on HEK‐293 cells stably expressing recombinant Ca~V~3.1 channels showed that T‐type currents were not affected by chronic exposure to the growth factors. These results suggest that muscle T‐channel downregulation by TGF‐β1 and BMP‐2 may be mediated by reduced transcription rather than through post‐transcriptional modifications of Ca~V~3.1 channels. J. Cell. Physiol. 209: 448–456, 2006. © 2006 Wiley‐Liss, Inc.