Project description: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. Experiment Overall Design: Immortalized B-cells from BMPR2 mutation carriers with and without disease are compared to search for modifier genes
Project description: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
Project description:BMPR2 mutation causes pulmonary arterial hypertension (PAH); ACE2 treatment can resolve established BMPR2-mediated PAH. The purpose of this study was to uncover the molecular mechanism behind this. Four groups: +/- ACE2 and +/- BMPR2 transgene, two arrays each, each array a pool of three animals.
Project description:BMPR2 mutation causes pulmonary arterial hypertension (PAH); ACE2 treatment can resolve established BMPR2-mediated PAH. The purpose of this study was to uncover the molecular mechanism behind this.
Project description:Pulmonary arterial hypertension (PAH) is thought to be driven by dysfunction of pulmonary vascular microendothelial cells (PMVEC). Most hereditary PAH is associated with BMPR2 mutations. However, the physiologic and molecular consequences of expression of BMPR2 mutations in PMVEC are unknown. PMVEC were isolated from triple transgenic mice carrying the immortomouse gene, a transactivator, and either control, Bmpr2delx4+ or Bmpr2R899X mutation
Project description:Vascular remodeling in pulmonary arterial hypertension (PAH) involves proliferation and migration of endothelial and smooth muscle cells, leading to obliterative vascular lesions. Previous studies have indicated that the endothelial cell proliferation is quasi-neoplastic, with evidence of monoclonality and instability of short DNA microsatellite sequences. To assess whether there is larger scale genomic instability, we performed genome-wide microarray copy number analysis on pulmonary artery endothelial (PAEC) and smooth muscle cells isolated from the lungs of PAH patients. Mosaic chromosomal abnormalities were detected in five of nine PAEC cultures from PAH lungs and zero of four controls. Fluorescent in situ hybridization analysis confirmed the presence of these abnormalities in vivo in two of three cases. One patient harbored a germline mutation of BMPR2, the primary genetic cause of PAH, and a somatic loss of chromosome-13, which constitutes a second hit in the same pathway by deleting Smad-8. In two female cases with mosaic loss of the X-chromosome, methylation analysis showed that the active X was deleted. Remarkably, one also showed completely skewed X-inactivation in the non-deleted cells, suggesting the PAEC population was clonal prior to the acquisition of the chromosome abnormality. Our data indicate a high frequency of genetically abnormal sub-clones within the lung vessels of patients with PAH and provide the first definitive evidence of a second genetic hit in a patient with a germline BMPR2 mutation. We propose that these chromosome abnormalities may confer a growth advantage and thus contribute to the progression of PAH. Cross-sectional study of genomic copy number in cells cultured from the lungs of PAH patients.
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.
Project description:Vascular remodeling in pulmonary arterial hypertension (PAH) involves proliferation and migration of endothelial and smooth muscle cells, leading to obliterative vascular lesions. Previous studies have indicated that the endothelial cell proliferation is quasi-neoplastic, with evidence of monoclonality and instability of short DNA microsatellite sequences. To assess whether there is larger scale genomic instability, we performed genome-wide microarray copy number analysis on pulmonary artery endothelial (PAEC) and smooth muscle cells isolated from the lungs of PAH patients. Mosaic chromosomal abnormalities were detected in five of nine PAEC cultures from PAH lungs and zero of four controls. Fluorescent in situ hybridization analysis confirmed the presence of these abnormalities in vivo in two of three cases. One patient harbored a germline mutation of BMPR2, the primary genetic cause of PAH, and a somatic loss of chromosome-13, which constitutes a second hit in the same pathway by deleting Smad-8. In two female cases with mosaic loss of the X-chromosome, methylation analysis showed that the active X was deleted. Remarkably, one also showed completely skewed X-inactivation in the non-deleted cells, suggesting the PAEC population was clonal prior to the acquisition of the chromosome abnormality. Our data indicate a high frequency of genetically abnormal sub-clones within the lung vessels of patients with PAH and provide the first definitive evidence of a second genetic hit in a patient with a germline BMPR2 mutation. We propose that these chromosome abnormalities may confer a growth advantage and thus contribute to the progression of PAH. Cross-sectional study of genomic copy number in cells cultured from the lungs of PAH patients. This study used three Affy SNP chip types: 250kNSP, 250kSTY, and 6.0
Project description:Vascular remodeling in pulmonary arterial hypertension (PAH) involves proliferation and migration of endothelial and smooth muscle cells, leading to obliterative vascular lesions. Previous studies have indicated that the endothelial cell proliferation is quasi-neoplastic, with evidence of monoclonality and instability of short DNA microsatellite sequences. To assess whether there is larger scale genomic instability, we performed genome-wide microarray copy number analysis on pulmonary artery endothelial (PAEC) and smooth muscle cells isolated from the lungs of PAH patients. Mosaic chromosomal abnormalities were detected in five of nine PAEC cultures from PAH lungs and zero of four controls. Fluorescent in situ hybridization analysis confirmed the presence of these abnormalities in vivo in two of three cases. One patient harbored a germline mutation of BMPR2, the primary genetic cause of PAH, and a somatic loss of chromosome-13, which constitutes a second hit in the same pathway by deleting Smad-8. In two female cases with mosaic loss of the X-chromosome, methylation analysis showed that the active X was deleted. Remarkably, one also showed completely skewed X-inactivation in the non-deleted cells, suggesting the PAEC population was clonal prior to the acquisition of the chromosome abnormality. Our data indicate a high frequency of genetically abnormal sub-clones within the lung vessels of patients with PAH and provide the first definitive evidence of a second genetic hit in a patient with a germline BMPR2 mutation. We propose that these chromosome abnormalities may confer a growth advantage and thus contribute to the progression of PAH.