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Poor vessel formation in embryos from knock-in mice expressing ALK5 with L45 loop mutation defective in Smad activation

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Author

  • Fumiko Itoh
  • Susumu Itoh
  • Rita L. C. Carvalho
  • Tomomi Adachi
  • Masatsugu Ema
  • Marie-Jose Goumans
  • Jonas Larsson
  • Stefan Karlsson
  • Satoru Takahashi
  • Christine L. Mummery
  • Peter ten Dijke
  • Mitsuyasu Kato
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Summary, in English

Transforming growth factor (TGF)-beta regulates vascular development through two type I receptors: activin receptor-like kinase (ALK) 1 and ALK5, each of which activates a different downstream Smad pathway. The endothelial cell (EC)-specific ALK1 increases EC proliferation and migration, whereas the ubiquitously expressed ALK5 inhibits both of these processes. As ALK1 requires the kinase activity of ALK5 for optimal activation, the lack of ALK5 in ECs results in defective phosphorylation of both Smad pathways on TGF-beta stimulation. To understand why TGF-beta signaling through ALK1 and ALK5 has opposing effects on ECs and whether this takes place in vivo, we carefully compared the phenotype of ALK5 knock-in (ALK5(KI/KI)) mice, in which the aspartic acid residue 266 in the L45 loop of ALK5 was replaced by an alanine residue, with the phenotypes of ALK5 knock-out (ALK5(-/-)) and wild-type mice. The ALK5(KI/KI) mice showed angiogenic defects with embryonic lethality at E10.5-11.5. Although the phenotype of the ALK5(KI/KI) mice was quite similar to that of the ALK5(-/-) mice, the hierarchical structure of blood vessels formed in the ALK5(KI/KI) embryos was more developed than that in the ALK5(-/-) mutants. Thus, the L45 loop mutation in ALK5 partially rescued the earliest vascular defects in the ALK5(-/-) embryos. This study supports our earlier observation that vascular maturation in vivo requires both TGF-beta/ALK1/BMP-Smad and TGF-beta/ALK5/activin-Smad pathways for normal vascular development. Laboratory Investigation (2009) 89, 800-810; doi:10.1038/labinvest.2009.37; published online 27 April 2009

Publishing year

2009

Language

English

Pages

800-810

Publication/Series

Laboratory Investigation

Volume

89

Issue

7

Document type

Journal article

Publisher

Nature Publishing Group

Topic

  • Hematology

Keywords

  • TGF-beta
  • endothelium
  • ALK1
  • ALK5
  • vasculature
  • yolk sac

Status

Published

ISBN/ISSN/Other

  • ISSN: 1530-0307