Overexpression of Activin Receptor-Like Kinase 1 in Endothelial Cells Suppresses Development of Arteriovenous Malformations in Mouse Models of Hereditary Hemorrhagic Telangiectasia

Circ Res. 2020 Oct 9;127(9):1122-1137. doi: 10.1161/CIRCRESAHA.119.316267. Epub 2020 Jul 31.


Rationale: Hereditary hemorrhagic telangiectasia (HHT) is a genetic disease caused by mutations in ENG, ALK1, or SMAD4. Since proteins from all 3 HHT genes are components of signal transduction of TGF-β (transforming growth factor β) family members, it has been hypothesized that HHT is a disease caused by defects in the ENG-ALK1-SMAD4 linear signaling. However, in vivo evidence supporting this hypothesis is scarce.

Objective: We tested this hypothesis and investigated the therapeutic effects and potential risks of induced-ALK1 or -ENG overexpression (OE) for HHT.

Methods and results: We generated a novel mouse allele (ROSA26Alk1) in which HA (human influenza hemagglutinin)-tagged ALK1 and bicistronic eGFP expression are induced by Cre activity. We examined whether ALK1-OE using the ROSA26Alk1 allele could suppress the development of arteriovenous malformations (AVMs) in wounded adult skin and developing retinas of Alk1- and Eng-inducible knockout (iKO) mice. We also used a similar approach to investigate whether ENG-OE could rescue AVMs. Biochemical and immunofluorescence analyses confirmed the Cre-dependent OE of the ALK1-HA transgene. We could not detect any pathological signs in ALK1-OE mice up to 3 months after induction. ALK1-OE prevented the development of retinal AVMs and wound-induced skin AVMs in Eng-iKO as well as Alk1-iKO mice. ALK1-OE normalized expression of SMAD and NOTCH target genes in ENG-deficient endothelial cells (ECs) and restored the effect of BMP9 (bone morphogenetic protein 9) on suppression of phosphor-AKT levels in these endothelial cells. On the other hand, ENG-OE could not inhibit the AVM development in Alk1-iKO models.

Conclusions: These data support the notion that ENG and ALK1 form a linear signaling pathway for the formation of a proper arteriovenous network during angiogenesis. We suggest that ALK1 OE or activation can be an effective therapeutic strategy for HHT. Further research is required to study whether this therapy could be translated into treatment for humans.

Keywords: activin receptor-like kinase 1; arteriovenous malformation; endoglin; endothelial cell; hereditary hemorrhagic telangiectasia; mice; signal transduction.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Activin Receptors, Type II / deficiency
  • Activin Receptors, Type II / genetics
  • Activin Receptors, Type II / metabolism*
  • Alleles
  • Animals
  • Apoptosis Regulatory Proteins / genetics
  • Apoptosis Regulatory Proteins / metabolism
  • Arteriovenous Malformations / genetics
  • Arteriovenous Malformations / prevention & control*
  • Disease Models, Animal
  • Endoglin / deficiency
  • Endoglin / genetics
  • Endoglin / metabolism
  • Endothelial Cells / metabolism*
  • Green Fluorescent Proteins / metabolism
  • Growth Differentiation Factor 2 / metabolism
  • Mice
  • Mitochondrial Proteins / genetics
  • Mitochondrial Proteins / metabolism
  • RNA, Untranslated
  • Receptors, Notch / genetics
  • Receptors, Notch / metabolism
  • Retinal Vessels / abnormalities
  • Signal Transduction
  • Skin / blood supply
  • Skin / injuries
  • Smad4 Protein / genetics
  • Smad4 Protein / metabolism
  • Telangiectasia, Hereditary Hemorrhagic / genetics
  • Telangiectasia, Hereditary Hemorrhagic / metabolism*
  • Transforming Growth Factor beta


  • Apoptosis Regulatory Proteins
  • Diablo protein, mouse
  • Endoglin
  • Eng protein, mouse
  • Growth Differentiation Factor 2
  • Gt(ROSA)26Sor non-coding RNA, mouse
  • Mitochondrial Proteins
  • RNA, Untranslated
  • Receptors, Notch
  • Smad4 Protein
  • Smad4 protein, mouse
  • Transforming Growth Factor beta
  • enhanced green fluorescent protein
  • Green Fluorescent Proteins
  • Activin Receptors, Type II
  • Acvrl1 protein, mouse