TGF-β3-dependent SMAD2 phosphorylation and inhibition of MEE proliferation during palatal fusion

Xiao Mei Cui, Yang Chai, Jucheng Chen, Tadashi Yamamoto, Yoshihiro Ito, Pablo Bringas, Charles F. Shuler

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56 Citations (Scopus)


Transforming growth factor (TGF)-β3 is known to selectively regulate the disappearance of murine medial edge epithelium (MEE) during palatal fusion. Previous studies suggested that the selective function of TGF-β3 in MEE was conducted by TGF-β receptors. Further studies were needed to demonstrate that the TGF-β signaling mediators were indeed expressed and phosphorylated in the MEE cells. SMAD2 and SMAD3 were both present in the MEE, whereas SMAD2 was the only one phosphorylated during palatal fusion. SMAD2 phosphorylation was temporospatially restricted to the MEE and correlated with the disappearance of the MEE. No phosphorylated SMAD2 was found in MEE in TGF-β3-/- mice, although nonphosphorylated SMAD2 was present. The results suggest that TGF-β3 is required for initiating and maintaining SMAD2 phosphorylation in MEE. Phospho-SMAD3 was not detectable in palate during normal palatal fusion. Previous results suggested TGF-β-induced cessation of DNA synthesis in MEE cells during palatal fusion in vitro. The present results provide evidence that inhibition of MEE proliferation in vivo was controlled by endogenous TGF-β3. The number of 5-bromo-2′-deoxyuridine (BrdU)-labeled MEE cells was significantly reduced in TGF-β3+/+ compared with TGF-β3-/- mice when the MEE seam formed (t-test, P < 0.05). This finding suggests that TGF-β3 is required for inhibiting MEE proliferation during palatal fusion. The inhibition of MEE proliferation may be mediated by TGF-β3-dependent phosphorylation of SMAD2.

Original languageEnglish
Pages (from-to)387-394
Number of pages8
JournalDevelopmental Dynamics
Issue number3
Publication statusPublished - Jul 1 2003
Externally publishedYes


  • Epithelial-mesenchymal transformation
  • Medial edge epithelium
  • Palatogenesis
  • Proliferation
  • SMAD2
  • SMAD3
  • TGF-β3

ASJC Scopus subject areas

  • Developmental Biology


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