Mechanisms of TGFbeta inhibition of LUNG endodermal morphogenesis: the role of TbetaRII, Smads, Nkx2.1 and Pten.
Transforming growth factor-beta is a multifunctional growth factor with roles in normal development and disease pathogenesis. One such role is in inhibition of lung branching morphogenesis, although the precise mechanism remains unknown. In an explant model, all three TGFbeta isoforms inhibited FGF10-induced morphogenesis of mesenchyme-free embryonic lung endoderm. Inhibition of budding by TGFbeta was partially abrogated in endodermal explants from Smad3(-/-) or conditional endodermal-specific Smad4(Delta/Delta) embryonic lungs. Endodermal explants from conditional TGFbeta receptor II knockout lungs were entirely refractive to TGFbeta-induced inhibition. Inhibition of morphogenesis was associated with dedifferentiation of endodermal cells as documented by a decrease in key transcriptional factor, NKX2.1 protein, and its downstream target, surfactant protein C (SpC). TGFbeta reduced the proliferation of wild-type endodermal cells within the explants as assessed by BrdU labeling. Gene expression analysis showed increased levels of mRNA for Pten, a key regulator of cell proliferation. Conditional, endodermal-specific deletion of Pten overcame TGFbeta's inhibitory effect on cell proliferation, but did not restore morphogenesis. Thus, the mechanisms by which TGFbeta inhibits FGF10-induced lung endodermal morphogenesis may entail both inhibition of cell proliferation, through increased Pten, as well as inhibition or interference with morphogenetic mediators such as Nkx2.1. Both of the latter are dependent on signaling through TbetaRII.
Xing
Yiming
Y
Department of Pediatrics, Division of Neonatology, University of Southern California, Keck School of Medicine, Los Angeles, CA 90033, USA.
Li
Changgong
C
Hu
Lingyan
L
Tiozzo
Caterina
C
Li
Min
M
Chai
Yang
Y
Bellusci
Saverio
S
Anderson
Stewart
S
Minoo
Parviz
P
D000818:Animals; D004707:Endoderm / Q000196:embryology*; D006801:Humans; D008168:Lung / Q000196:embryology*; D051379:Mice; D008817:Mice, Mutant Strains; D009024:Morphogenesis; D009687:Nuclear Proteins / Q000502:physiology*; D051059:PTEN Phosphohydrolase / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000502:physiology*; D051896:Smad Proteins, Receptor-Regulated / Q000502:physiology; D051900:Smad3 Protein; D051901:Smad4 Protein; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000502:physiology*; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*
C000614414:Nkx2-1 protein, mouse; D009687:Nuclear Proteins; D018125:Receptors, Transforming Growth Factor beta; D051896:Smad Proteins, Receptor-Regulated; D051900:Smad3 Protein; D051901:Smad4 Protein; C508960:TGFB1 protein, human; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors; D053773:Transforming Growth Factor beta1; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II; D051059:PTEN Phosphohydrolase; C487757:Pten protein, mouse