Together, these findings suggest that the BMP receptor type II/ALK-1/SMAD/ATOH8 axis may attenuate hypoxic responses in ECs in the pulmonary circulation and may help prevent the development of PAH.
Hereditary hemorrhagic telangiectasia (HTT) is an autosomal dominant disease, most frequently caused by a mutation in either ENG or ACVRL1, which can be associated with pulmonary arterial hypertension (PAH).
These results indicate that ALK-1 and Smad1 participate in the formation of PAH and the process of PVR, and suggest that NAC may inhibit PAH by inhibiting the expression of ALK-1 and Smad1 in the pulmonary artery.
However, current guidelines, clinical practices, and available gene panels focus the diagnosis of PAH on a relatively low number of genes and variants associated with the bone morphogenic proteins and transforming Growth Factor-β pathways, such as the BMPR2, ACVRL1, CAV1, ENG, and SMAD9.
Heritable pulmonary arterial hypertension (PAH) is an autosomal dominant disease with incomplete penetrance because of mutations in bone morphogenetic protein receptor-II (BMPR2), activin A receptor type II-like kinase 1, endoglin, caveolin-1, potassium channel subfamily K, member 3, and T-box gene 4 genes.
Therefore, our findings demonstrated that missense mutations of ACVRL1 identified in the present study significantly affected the bone morphogenetic protein 9 (BMP-9) pathway, implicating PAH pathogenesis.
Genetic causes of pulmonary arterial hypertension (PAH) and pulmonary veno-occlusive disease (PVOD) have been identified, leading to a growing need for genetic counselling.Between 2003 and 2014, genetic counselling was offered to 529 PAH and 100 PVOD patients at the French Referral Centre for Pulmonary Hypertension.Mutations in PAH-predisposing genes were identified in 72 patients presenting as sporadic PAH (17% of cases; 62 mutations in BMPR2, nine in ACVRL1 (ALK1) and one in ENG) and in 94 patients with a PAH family history (89% of cases; 89 mutations in BMPR2, three in ACVRL1 (ALK1) and two in KCNK3).
Specifically, studies have confirmed activin A receptor type II-like 1 (ACVRL1), endoglin (ENG), and members of the SMAD family as contributing to PAH both with and without associated clinical phenotypes.
The aim of this study was to analyze the Bone Morphogenetic Protein Receptor 2 (BMPR2), Activin A type II receptor like kinase 1 (ALK1/ACVRL1) and potassium voltage-gated channel, shakerrelated subfamily, member 5 (KCNA5) genes in patients with idiopathic and associated PAH.
To determine whether the TGF-β/ALK1/ENG pathway was involved in PAH, we investigated pulmonary TGF-β, ALK1, ALK5, and ENG expressions in human lung tissue and cultured pulmonary-artery smooth-muscle-cells (PA-SMCs) and pulmonary endothelial cells (PECs) from 14 patients with idiopathic PAH (iPAH) and 15 controls.
Since the landmark discovery that bone morphogenetic protein receptor type II (BMPR2) mutations cause the majority of cases of familial PAH, investigators have discovered mutations in genes that cause PAH in families without BMPR2 mutations, including the type I receptor ACVRL1 and the type III receptor ENG (both associated with hereditary hemorrhagic telangiectasia), caveolin-1 (CAV1), and a gene (KCNK3) encoding a two-pore potassium channel.
Among them, the identification of bone morphogenetic protein receptor type 2 (BMPR2) as the major predisposing gene and activin A receptor type II-like kinase-1 (ACVRL1, also known as ALK1) as the major gene when PAH is associated with hereditary hemorrhagic telangiectasia.
We studied a family in which multiple members had pulmonary arterial hypertension without identifiable mutations in any of the genes known to be associated with the disease, including BMPR2, ALK1, ENG, SMAD9, and CAV1.
Heritable and idiopathic pulmonary arterial hypertension (PAH) are phenotypically identical and associated with mutations in several genes related to transforming growth factor (TGF) beta signaling, including bone morphogenetic protein receptor type 2, activin receptor-like kinase 1, endoglin, and mothers against decapentaplegic 9.
We report a remarkable ACVRL1 germinal and somatic mosaicism characterized by the presence of two distinct mutant alleles and a non-mutant ACVRL1 allele in a woman diagnosed with PAH at the age 40.
ACVRL1 mutations in exon 10 were more frequently observed in patients with PAH, as compared with what was observed in the HHT Mutation Database (33.3 vs. 5%; P < 0.0001).
This report highlights ALK1 mutations associated with a variable PAH phenotype, including pulmonary arteriovenous malformations and severe PAH presenting early in life.
Since both the BMPR2 and ALK1 belonging to the transforming growth factor (TGF)-beta superfamily are known to predispose to PAH, mutations in other genes of the TGF-beta/BMP signalling pathways may also predispose to PAH.
Furthermore, asymptomatic carriers with the ALK1 mutation within the serine - threonine kinase domain are at risk of developing PAH and hereditary hemorrhagic telangiectasia, so close follow-up is recommended for those individuals.