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BMPR2 mutation carriers with and without evidence of PAH

ABSTRACT: Background: While BMPR2 mutation strongly predisposes to pulmonary arterial hypertension (PAH), only 20% of mutation carriers develop clinical disease. This finding suggests that modifier genes contribute to FPAH clinical expression. Since modifiers are likely to be common alleles, this problem is not tractable by traditional genetic approaches. Further, examination of gene expression is complicated by confounding effects attributable to drugs and the disease process itself. Methods: To resolve these problems, B-cells were isolated, EBV-immortalized, and cultured from familial PAH patients with BMPR2 mutations, mutation positive but disease-free family members, and family members without mutation. This allows examination of differences in gene expression without drug or disease-related effects. These differences were assayed by Affymetrix array, with follow-up by quantitative RT-PCR and additional statistical analyses. Results: By gene array, we found consistent alterations in multiple pathways with known relationship to PAH, including actin organization, immune function, calcium balance, growth, and apoptosis. Selected genes were verified by quantitative RT-PCR using a larger sample set. Analysis of overrepresented gene ontology groups suggests that it is pathway-specific, not gene-specific changes that carry increased risk of disease. Conclusions: B-cell lines are a valuable and accessible tool for assaying alterations in gene expression free from drug and disease effects. Predisposition to disease within BMPR2 mutation carriers was linked to several pathways, including proliferation, GTP signaling, and stress response. Keywords: Search for modifier genes

ORGANISM(S): Homo sapiens

PROVIDER: GSE10767 | GEO | 2008/09/01

SECONDARY ACCESSION(S): PRJNA107557

REPOSITORIES: GEO

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Project description:Bmpr2 mutations are critical risk factors for hereditary pulmonary arterial hypertension (hPAH) with approximately 20% of carriers developing disease. There is an unmet medical need to understand how environmental factors, such as inflammation, render Bmpr2 mutants susceptible to PAH. Overexpressing 5-lipoxygenase (5-LO) provokes lung inflammation and transient PAH in Bmpr2+/- mice. Accordingly, 5-LO and its metabolite, leukotriene B4 (LTB4), are candidates for the ‘second hit’. The purpose of this study was to determine how 5-LO-mediated pulmonary inflammation synergized with phenotypically-silent Bmpr2 defects to elicit significant pulmonary vascular disease in rats. Monoallelic Bmpr2 mutant rats were generated and found phenotypically normal for up to one year of observation. To evaluate whether a second hit would elicit disease, animals were exposed to 5-LO-expressing adenovirus (AdAlox5), monocrotaline, SU5416 or chronic hypoxia and analyzed. Bmpr2-mutant hPAH patient samples were assessed for neointimal 5-LO expression. Pulmonary artery endothelial cells (PAECs) were cultured with lentivirus expressing short hairpin RNA (shRNA) targeting Bmpr2 (shBmpr2) to model the impaired BMPR2 signaling, and were then exposed to 5-LO-expressing adenovirus (AdAlox5), and were assessed for phenotypic and transcriptomic changes. In vitro, BMPR2 deficiency, compounded by 5-LO-mediated inflammation, generated apoptosis-resistant and proliferative PAECs with mesenchymal characteristics. These transformed cells expressed nuclear envelop-localized 5-LO consistent with induced LTB4 production, as well as a transcriptomic signature similar to clinical disease, including upregulated NF-kB, IL-6 and TGF-β signaling pathways. The reversal of PAH and vasculopathy in Bmpr2 mutants by TGF-β antagonism suggests that TGF-β is critical for neointimal transformation. Thus, in a new two-hit model of disease, lung inflammation induced severe PAH pathology in Bmpr2+/- rats. Endothelial transformation required the activation of canonical and noncanonical TGF-β signaling pathways and was characterized by 5-LO nuclear envelope translocation with enhanced LTB4 production. This study offers one explanation of how an environmental injury unleashes the destructive potential of an otherwise-silent genetic mutation.

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BMPR2 mutation carriers with and without evidence of PAH

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