TGFβ3 is expressed in differentiating muscle of the embryonic mouse tongue

The purpose of the present study was to elucidate the involvement of transforming growth factor betas (TGF beta s) in the differentiation of tongue striated muscles by analyzing the expression of TGF beta s, their receptors and factors of TGF beta signal transduction in the mouse tongue between embryonic days 11 (E11) and E15. The expression levels of TGF beta 3 mRNA and protein were much higher than those of TGF beta 1 and TGF beta 2, and the immunolocalization of TGF beta 3 was more consistent with the differentiating muscle cells in comparison with those of TGF beta 1 and 2 between E12 and E15. TGF beta RI and II were localized to the differentiating muscle cells between E11 and E15. Phosphorylated-smad2/3 was localized to the nucleus of muscle cells which just began to differentiate. These results suggest that the signal of TGF beta 3, but not that of beta 1 or beta 2, may be involved in the early stages (particularly the beginning) of differentiation of mouse tongue muscle cells through TGF beta RI, TGF beta RII, and smad2/3.