Transforming growth factor-beta3-induced Smad signaling regulates actin reorganization during chondrogenesis of chick leg bud mesenchymal cells.

Endochondral ossification is characterized by a significant interdependence between cell shape and cytoskeletal organization that accompanies the onset of chondrogenic signaling. However, the mechanisms mediating these interactions have not been well studied. Here, treatment with transforming growth factor (TGF)-beta3 at a later stage of chondrogenesis led to activation of Smad-2 signaling and the formation of intense stress fibers, which resulted in suppressing chondrogenic differentiation of leg bud mesenchymal cells. Moreover, specific siRNA knockdown of Smad-2 reduced TGF-beta3-induced stress fibers via physical interactions with beta-catenin. In conclusion, our results indicate that TGF-beta3-induced Smad signaling, in conjunction with beta-catenin, is involved in the reorganization of the actin cytoskeleton into a cortical pattern with a concomitant rounding of cells. J. Cell. Biochem. (c) 2009 Wiley-Liss, Inc.This article was published online on 28 May 2009. An error was subsequently identified. This notice is included in the online and print versions to indicate that both have been corrected 8 June 2009.