Poor vessel formation in embryos from knock-in mice expressing ALK5 with L45 loop mutation defective in Smad activation.
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.
Itoh
Fumiko
F
Department of Experimental Pathology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
Itoh
Susumu
S
Carvalho
Rita L C
RL
Adachi
Tomomi
T
Ema
Masatsugu
M
Goumans
Marie-José
MJ
Larsson
Jonas
J
Karlsson
Stefan
S
Takahashi
Satoru
S
Mummery
Christine L
CL
Dijke
Peter Ten
PT
Kato
Mitsuyasu
M
D030201:Activin Receptors, Type I / Q000378:metabolism; D030301:Activin Receptors, Type II; D019943:Amino Acid Substitution; D000818:Animals; D001483:Base Sequence; D001808:Blood Vessels / Q000002:abnormalities* / Q000196:embryology / Q000378:metabolism; D003114:Colony-Forming Units Assay; D017931:DNA Primers / Q000235:genetics; D005260:Female; D006330:Heart Defects, Congenital / Q000196:embryology / Q000235:genetics / Q000378:metabolism; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008817:Mice, Mutant Strains; D008822:Mice, Transgenic; D016297:Mutagenesis, Site-Directed; D018919:Neovascularization, Physiologic / Q000235:genetics; D010641:Phenotype; D011247:Pregnancy; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000172:deficiency / Q000235:genetics* / Q000502:physiology*; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000737:chemistry / Q000172:deficiency / Q000235:genetics* / Q000502:physiology*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D051785:Smad Proteins / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism; D015017:Yolk Sac / Q000002:abnormalities / Q000098:blood supply / Q000196:embryology / Q000378:metabolism
D017931:DNA Primers; D018125:Receptors, Transforming Growth Factor beta; D011994:Recombinant Proteins; D051785:Smad Proteins; D016212:Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D030201:Activin Receptors, Type I; D030301:Activin Receptors, Type II; C498931:Acvrl1 protein, mouse; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625841:TGFBR1 protein, human; C000625842:Tgfbr1 protein, mouse