Developmentally regulated expression of Smad3, Smad4, Smad6, and Smad7 involved in TGF-beta signaling

Transforming growth factor-beta (TGF-beta ) signaling is mediated from seri ne/threonine kinase receptors to transcriptional responses via Smad protein s. Here comparison of mRNA expression of Smad3-7 in mouse embryos (E9-E15) revealed developmentally regulated distinct expression patterns for Smad3, 4, 6, and 7. Smad3 was prominently expressed in the differentiating (from E 10) central nervous system, but also in developing bones, branchial arches and epithelium of various tissues. Smad4 mostly showed ubiquitous expressio n, but in E15 embryos, a pronounced signal appeared in epithelial crypts of the gut. Inhibitory Smad6 and Smad7 were coexpressed at high levels in dev eloping cardiovascular system from the earliest stages studied. In contrast . Smad6 was selectively expressed at high levels, e.g. in intramembranous b one whereas Smad7 was prominent in seminiferous tubules of the testis, demo nstrating distinct expression of these genes in non-cardiovascular tissues. (C) 2001 Elsevier Science ireland Ltd. All rights reserved.