title: Enhanced responses to angiogenic cues underlie the pathogenesis of hereditary hemorrhagic telangiectasia 2.
abstract: Hereditary Hemorrhagic Telangiectasia (HHT) is a genetic vascular disease in which arteriovenous malformations (AVMs) manifest in skin and multiple visceral organs. HHT is caused by heterozygous mutations in endoglin (ENG), activin receptor-like kinase 1 (ALK1), or SMAD4. ALK1 regulates angiogenesis, but the precise function of ALK1 in endothelial cells (ECs) remains elusive. Since most blood vessels of HHT patients do not produce pathological vascular lesions, ALK1 heterozygous ECs may be normal unless additional genetic or environmental stresses are imposed. To investigate the cellular and biochemical phenotypes of Alk1-null versus Alk1-heterozygous ECs, we have generated pulmonary EC lines in which a genotype switch from the Alk1-conditional allele (Alk1 (2f)) to the Alk1-null allele (Alk1 (1f)) can be induced by tamoxifen treatment. Alk1-null (1 f/1 f) ECs displayed increased migratory properties in vitro in response to bFGF compared with Alk1-het (2 f/1 f) ECs. The 1 f/1 f-ECs formed a denser and more persistent tubular network as compared with their parental 2 f/1 f-ECs. Interestingly, the response to BMP-9 on SMAD1/5 phosphorylation was impaired in both 2 f/1 f- and 1 f/1 f-ECs at a comparable manner, suggesting that other factors in addition to SMADs may play a crucial role for enhanced angiogenic activity in 1 f/1 f-ECs. We also demonstrated in vivo that Alk1-deficient ECs exhibited high migratory and invasive properties. Taken together, these data suggest that enhanced responses to angiogenic cues in ALK1-deficient ECs underlie the pathogenesis of HHT2.
authors.affiliation: Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Eun-Jung
authors.initials: EJ
authors.lastname: Choi
authors.forename: Yong Hwan
authors.initials: YH
authors.lastname: Kim
authors.forename: Se-woon
authors.initials: SW
authors.lastname: Choe
authors.forename: Yu Gyoung
authors.initials: YG
authors.lastname: Tak
authors.forename: Eva M
authors.initials: EM
authors.lastname: Garrido-Martin
authors.forename: Myron
authors.initials: M
authors.lastname: Chang
authors.forename: Young Jae
authors.initials: YJ
authors.lastname: Lee
authors.forename: S Paul
authors.initials: SP
authors.lastname: Oh
mesh_terms: D030201:Activin Receptors, Type I / Q000235:genetics*; D000818:Animals; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects / Q000235:genetics; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D055786:Gene Knockout Techniques; D023061:Gene Order; D018390:Gene Targeting; D005838:Genotype; D055427:Growth Differentiation Factor 2 / Q000378:metabolism; D006801:Humans; D018345:Mice, Knockout; D009389:Neovascularization, Pathologic / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D051785:Smad Proteins / Q000378:metabolism; D013683:Telangiectasia, Hereditary Hemorrhagic / Q000235:genetics* / Q000378:metabolism / Q000473:pathology
chemical_list: D055427:Growth Differentiation Factor 2; D051785:Smad Proteins; D016222:Fibroblast Growth Factor 2; D030201:Activin Receptors, Type I