A new nonsense mutation of SMAD8 associated with pulmonary arterial hypertension

International Research and Educational Institute for Integrated Medical Sciences (IREIIMS), Tokyo Women's Medical University, Shinjuku-ku, Tokyo, Japan.
Journal of Medical Genetics (Impact Factor: 6.34). 02/2009; 46(5):331-7. DOI: 10.1136/jmg.2008.062703
Source: PubMed


Pulmonary arterial hypertension (PAH) is a progressive disorder characterised by raised pulmonary artery pressures with pathological changes in small pulmonary arteries. Previous studies have shown that approximately 70% of familial PAH and also 11-40% of idiopathic PAH (IPAH) cases have mutations in the bone morphogenetic protein receptor type II (BMPR2) gene. In addition, mutations in the activin receptor-like kinase 1 (ALK1) gene have been reported in PAH patients. 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.
We screened for mutations in ENDOGLIN(ENG), SMAD1, SMAD2, SMAD3, SMAD4, SMAD5, SMAD6 and SMAD8 genes, which are involved in the TGF-beta/BMP signallings, in 23 patients with IPAH who had no mutations in BMPR2 or ALK1.
A nonsense mutation in SMAD8 designated c.606 C>A, p.C202X was identified in one patient. The father of this patient was also identified as having the same mutation. Functional analysis showed the truncated form of the SMAD8 C202X protein was not phosphorylated by constitutively active ALK3 and ALK1. The SMAD8 mutant was also unable to interact with SMAD4. The response to BMP was analysed using promoter-reporter activities with SMAD4 and/or ca-ALK3. The transcriptional activation of the SMAD8 mutant was inefficient compared with the SMAD8 wild type.
We describe the first mutation in SMAD8 in a patient with IPAH. Our findings suggest the involvement of SMAD8 in the pathogenesis of PAH.

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Available from: Hisato Yagi
    • "However, these analyses did not investigate SMAD-independent pathways, implicated in disease pathogenesis, leaving open the possibility that the identified variants may deleteriously affect other BMP related systems. By contrast, SMAD9 mutations (PPH2; MIM# 615342) lead to a marked reduction of SMAD transcriptional activity and a downregulation of the BMP target gene Id1 [Shintani et al., 2009; Nasim et al., 2011]. Of interest, heterozygous SMAD9 mutations have been observed to perturb non-canonical downstream pathways, in particular, micro-RNA (miRNA) processing. "
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    ABSTRACT: Pulmonary arterial hypertension (PAH) is an often fatal disorder resulting from several causes including heterogeneous genetic defects. While mutations in the bone morphogenetic protein receptor type II (BMPR2) gene are the single most common causal factor for hereditary cases, pathogenic mutations have been observed in approximately 25% of idiopathic PAH patients without a prior family history of disease. Additional defects of the transforming growth factor beta (TGF-β) pathway have been implicated in disease pathogenesis. 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. Most recently, next-generation sequencing has identified novel, rare genetic variation implicated in the PAH disease spectrum. Of importance, several identified genetic factors converge on related pathways and provide significant insight into the development, maintenance and pathogenetic transformation of the pulmonary vascular bed. Together, these analyses represent the largest comprehensive compilation of BMPR2 and associated genetic risk factors for PAH, comprising known and novel variation. Additionally, with the inclusion of an allelic series of locus-specific variation in BMPR2, these data provide a key resource in data interpretation and development of contemporary therapeutic and diagnostic tools. This article is protected by copyright. All rights reserved.
    No preview · Article · Sep 2015 · Human Mutation
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    • "Other genes than BMPR2 have been implicated in rare cases of PAH. Mutations in bone morphogenetic protein receptor 1B (BMPR1B), activin-like kinase-type 1 (AC- VRL1; ALK1), endoglin (ENG), smad family member 9 (SMAD9), caveolin 1 (CAV1), potassium channel subfamily K, member 3 (KCNK3), and NOTCH3 have been described in the development of the disease (Austin et al. 2012; Chaouat et al. 2004; Chida et al. 2012a; Harrison et al. 2003; Li et al. 2009; Ma et al. 2013; Shintani et al. 2009). The role of these genes in the pathogenesis of IPAH and HPAH is suggested significantly smaller compared to BMPR2. "
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    ABSTRACT: The genetic basis of pulmonary arterial hypertension (PAH) among Finnish PAH patients is poorly understood. We adopted a novel-targeted next-generation sequencing (NGS) approach called Oligonucleotide-Selective Sequencing (OS-Seq) and developed a custom data analysis and interpretation pipeline to identify pathogenic base substitutions, insertions, and deletions in seven genes associated with PAH (BMPR2, BMPR1B, ACVRL1, ENG, SMAD9, CAV1, and KCNK3) from Finnish PAH patients. This study represents the first clinical study with OS-Seq technology on patients suffering from a rare genetic disorder. We analyzed DNA samples from 21 Finnish PAH patients, whose BMPR2 and ACVRL1 mutation status had been previously studied using Sanger sequencing. Our sequencing panel covered 100% of the targeted base pairs with >15× sequencing depth. Pathogenic base substitutions were identified in the BMPR2 gene in 29% of the Finnish PAH cases. Two of the pathogenic variant-positive patients had been previously tested negative using Sanger sequencing. No clinically significant variants were identified in the six other PAH genes. Our study validates the use of targeted OS-Seq for genetic diagnostics of PAH and revealed pathogenic variants that had been previously missed using Sanger sequencing.
    Full-text · Article · Apr 2015
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    • "Over the last 10 years, the importance of ALK1 and ENG in the pathogenesis of PAH has been established, notably by the identification of gene mutations [2], [16]. More recently, a nonsense mutation of Smad8, a component of the TGF-β/ALK1/ENG signaling pathway, was described in a patient with iPAH [17]. Data on the role for the TGF/ALK1 pathway in experimental models are conflicting. "
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    ABSTRACT: Mutations affecting transforming growth factor-beta (TGF-β) superfamily receptors, activin receptor-like kinase (ALK)-1, and endoglin (ENG) occur in patients with pulmonary arterial hypertension (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. Seeing that ENG was highly expressed in PEC, we assessed the effects of TGF-β on Smad1/5/8 and Smad2/3 activation and on growth factor production by the cells. Finally, we studied the consequence of ENG deficiency on the chronic hypoxic-PH development by measuring right ventricular (RV) systolic pressure (RVSP), RV hypertrophy, and pulmonary arteriolar remodeling in ENG-deficient (Eng+/-) and wild-type (Eng+/+) mice. We also evaluated the pulmonary blood vessel density, macrophage infiltration, and cytokine expression in the lungs of the animals. Compared to controls, iPAH patients had higher serum and pulmonary TGF-β levels and increased ALK1 and ENG expressions in lung tissue, predominantly in PECs. Incubation of the cells with TGF-β led to Smad1/5/8 phosphorylation and to a production of FGF2, PDGFb and endothelin-inducing PA-SMC growth. Endoglin deficiency protected mice from hypoxic PH. As compared to wild-type, Eng+/- mice had a lower pulmonary vessel density, and no change in macrophage infiltration after exposure to chronic hypoxia despite the higher pulmonary expressions of interleukin-6 and monocyte chemoattractant protein-1. The TGF-β/ALK1/ENG signaling pathway plays a key role in iPAH and experimental hypoxic PH via a direct effect on PECs leading to production of growth factors and inflammatory cytokines involved in the pathogenesis of PAH.
    Full-text · Article · Jun 2014 · PLoS ONE
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