Immunodetection of the transforming growth factors beta 1 and beta 2 in the developing murine palate

The expression of some members of the TGF beta family of genes in embryonic craniofacial tissue suggests a functional role for these molecules in orofacial development. In other systems, TGF beta 1 and TGF beta 2 have been shown to regulate cell proliferation and extracellular matrix metabolism, processes critical to normal development of the secondary palate. We have thus determined the amount and tissue distribution of both TGF beta 1 and TGF beta 2 in embryonic palatal tissue. Cellular extracts of murine embryonic palatal tissue from days 12, 13 and 14 of gestation were assayed for the presence of TGF beta 1 and TGF beta 2 by immunoprecipitation. Physiological levels, ranging from 0.05-20 ng/micrograms protein, of both growth factors were detected in all tissues examined. Immunostaining with antibodies directed against either TGF beta 1 or TGF beta 2 demonstrated the presence of these growth factors in palatal epithelium and mesenchyme early during palatal development (gestational day [GD] 12) a period characterized by tissue growth. On GDs 13 and 14, characterized by palate epithelial differentiation, immunostaining for both growth factors predominated in epithelial tissue. Immunostaining for TGF beta 1 and TGF beta 2 was also intense in mesenchyme surrounding tooth germs and in perichondrium. Chondrocytes and cartilage extracellular matrix did not stain for either TGF beta 1 or beta 2. Combined with existing evidence for the presence of functional receptors for the transforming growth factor-beta s in the developing palate, these results provide rationale for studies designed to clarify a specific role for these signalling molecules in palate epithelial differentiation and/or epithelial-mesenchymal interactions.