Bone Morphogenetic Protein Receptor Type 2 Mutation Research Articles

BMPR2 variants in pulmonary arterial hypertension. Are they really worrisome?

Abstract Background Pulmonary arterial hypertension (PAH) is a rare and severe disease. The discovery of the gene encoding Bone Morphogenetic Protein Receptor Type 2 (BMPR2) in 2000 was the first evidence of an association between genetics and PAH. BMPR2 mutation carriers are younger and have higher haemodynamic severity, determining higher risk than sporadic cases. In the last few years, novel genetic variants have been identified. The risk of mortality of the currently known mutations is scarce. Purpose To describe the role of gene variants regarding long-term survival in a cohort of PAH patients. Methods We included patients diagnosed with PAH between January 2011-December 2020, following the ESC/ERC Guidelines recommendations. At least one genetic study was available in included individuals. Pulmonary venooclusive disease, PAH associated with congenital heart disease, or connective tissue disorders were excluded. Three groups were compared: no mutation, BMPR2 carriers and other genetic variants. Comparison of qualitative and quantitative variables was done by Chi-square test and ANOVA test, respectively. Crude and adjusted Log-rank test was performed for the evaluation of mortality. Results 361 were finally included. The most frequent gene variant was BMPR2. Among the eight other gene variants, there were 2 cases of KCKN3, 2 of ACVRL1, and 1 case of KCNA5, TBX4, CPS1, and GDF2. BMPR2 and the rest of mutation carriers were younger at diagnosis and had worse haemodynamic parameters than non-carriers. Nevertheless, these patients tended to perform higher distances in the 6-minute walk test. Interestingly, BMPR2 patients had higher DLCO values at diagnosis (table). After 104.1±77.2 months of follow-up, there was a tendency for BMPR2 carriers toward lower crude free survival of mortality or lung transplantation. Nevertheless, this survival benefit disappears when adjusted by age (Table, figure). Conclusions The diagnostic yields of genetic analysis for pathogenic or likely pathogenic variants in idiopathic PAH are approximately 11%. BMPR2 is the most frequent causal gene. These patients are associated with marked haemodynamic impairment. Nevertheless, its younger age probably determines the better long-term results regarding mortality or lung transplantation observed when comparing these results with sporadic patients or those carrying other mutations. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Rio Hortega grant. Instituto de Salud Carlos III (ISCIII), Ministry of Science and Innovation, Spanish Government.

Clinical characteristics and prognosis analysis of idiopathic and hereditary pulmonary hypertension patients with ACVRL1 gene mutations.

Pulmonary arterial hypertension is a kind of heart and lung vascular disease with low incidence and poor prognosis. Genetic variants are the important factors of pulmonary arterial hypertension. The mutations of activin receptor-like kinase-1 (ACVRL1) could cause pulmonary arteriole obstruction and occlusion in pulmonary arterial hypertension patients. The ACVRL1 gene mutation and clinical characteristics of Chinese idiopathic or hereditary pulmonary hypertension (IPAH/HPAH) patients are still unclear. This study aimed to retrospectively study the mutation characteristics of ACVRL1 gene in Chinese IPAH/HPAH patients and its effect on clinical prognosis. We analyzed the clinical, functional, hemodynamic and mutation characteristics of 12 IPAH/HPAH patients with ACVRL1 mutations and compared with 94 IPAH/HPAH patients (27 patients carried bone morphogenetic protein receptor type 2 (BMPR2) mutations and 67 without mutations). All ACVRL1 mutations of 12 patients were single nucleotide missense mutations. The ratio of male to female in 12 patients was 1:1. The diagnosis age of ACVRL1 mutation patients was younger than that of BMPR2 mutation patients (13.6 ± 11.3 years vs. 16.0 ± 12.9 years) but higher than that of patients without mutations (13.6 ± 11.3 years vs. 8.8 ± 8.5 years, p = 0.006). IPAH/HPAH patients with ACVRL1 mutation have rapid disease progresses, high overall mortality rate (approximately 50%) and no response to the acute pulmonary vasodilation test. In conclusion, this is the first study to analyze the ACVRL1 gene mutation and clinical characteristics of Chinese IPAH/HPAH patients. It is beneficial to screen ACVRL1 gene mutation for IPAH/HPAH patients to facilitate genetic counseling and early prevention and treatment.

Alteration of Extracellular Superoxide Dismutase in Idiopathic Pulmonary Arterial Hypertension

Background: Superoxide dismutases (SODs) are an important family of antioxidant enzymes that modulate reactive oxygen species levels. It is largely unknown which SOD isoform(s) change in vivo in idiopathic pulmonary arterial hypertension (IPAH) patients.Methods: A total of 133 consecutive adult IPAH patients who underwent bone morphogenetic protein receptor type 2 (BMPR2) genetic counseling were enrolled in this prospective study. The plasma activities of three subtypes of SOD [copper–zinc (Cu/Zn-SOD), manganese (Mn-SOD), and extracellular SOD (Ec-SOD)] were examined.Results: The activities of SODs were significantly lower in IPAH patients than in healthy subjects. However, only Ec-SOD activity in BMPR2 mutation patients was significantly decreased compared to those in patients without a mutation. The reduced Ec-SOD activity was markedly associated with mean pulmonary arterial pressure, pulmonary vascular resistance (PVR), and 6-min walking distance (6MWD). The reduction of Mn-SOD activity was only associated with 6MWD. There was no association between Cu/Zn-SOD and hemodynamics. Patients with a lower Ec-SOD level had a worse survival compared to those with a higher baseline. The reduced Ec-SOD activity and the raised PVR increased the mortality risk.Conclusions: Ec-SOD was correlated with BMPR2 mutation, hemodynamic dysfunction, and poor outcomes. Circulating Ec-SOD could be a potentially vital antioxidant enzyme in the pathogenesis of IPAH.

Prognostic Value of Gamma-Glutamyltransferase in Male Patients With Idiopathic Pulmonary Arterial Hypertension.

Background: The elevated gamma-glutamyltransferase (GGT) activity is regarded as an indicator of cardiovascular disease, with males having higher values than females. The greater incidence of idiopathic pulmonary arterial hypertension (IPAH) is observed in women, whereas prognosis is poor in men. The present study aims to investigate the potential association of GGT on male patients.Methods: Serum GGT levels were measured in 338 consecutive adult IPAH patients, who underwent bone morphogenetic protein receptor type 2 (BMPR2) genetic counseling, and matched with healthy subjects by sex and age. The followed interval was 48 ± 34 months.Results: Increased serum GGT levels were more common in patients with IPAH than controls (p < 0.001). GGT values were significantly higher in male patients than those of females (p < 0.001). Compared with female patients with BMPR2 mutation, GGT level in male patients with BMPR2 mutation was further increased (p = 0.002). Higher GGT levels were associated with worse hemodynamics and Nterminal pro B-type natriuretic peptide in all patients. However, males with a GGT concentration ≥ 53 U/L had a worse survival than those of females. Contrarily, if GGT concentration <53 U/L, there was no survival difference between male and female patients. After adjustment for relevant variables of clinical features and hemodynamics, baseline higher GGT levels remained increased risks of all-cause mortality in males rather than females. During rehospitalization follow-up, male patients still had significantly higher values of GGT than females.Conclusions: Increased GGT levels were correlated with BMPR2 mutation, hemodynamic dysfunction, and poor outcomes in male patients with IPAH. Further studies are needed to explain the origin of abnormal GGT and its potential pathogenesis in men.

Prevalence and clinical features of bone morphogenetic protein receptor type 2 mutation in Korean idiopathic pulmonary arterial hypertension patients: The PILGRIM explorative cohort.

BackgroundPulmonary arterial hypertension (PAH) is a progressive chronic disease with poor outcomes. One reason for poor prognosis is the lack of understanding regarding individual variability in response to treatment. Idiopathic PAH (IPAH) patients with bone morphogenetic protein receptor type 2 (BMPR2) mutations have distinct phenotypes that are crucial for individualized therapy but evidence regarding their prevalence and clinical features in the Korean population is lacking. Therefore, the present study aimed to screen Korean IPAH patients for BMPR2 mutations and analyze their clinical phenotypes.MethodsWe enrolled 73 unrelated IPAH patients for BMPR2 mutation screening between March 2010 to November 2015 from 11 hospitals in Korea. Thirty-three lineal family members from 6 families of BMPR2 mutation carriers were also screened.ResultsAmong 73 patients, 16 (22%) had BMPR2 mutations. Mutation carriers were younger (27 vs. 47 years; p = 0.02) and had a higher mean pulmonary arterial pressure (mPAP) than non-carriers (64 vs. 51 mmHg; p<0.05). Of the 16 individuals with mutations, 5 deletion, 2 splice-site, 6 nonsense, and 3 missense mutations were found, among which, 9 were newly identified mutation types. Patients less than 30 years old had more BMPR2 mutations (44 vs. 14%; p = 0.04) and a higher mPAP (64 vs. 50 mmHg; p = 0.04) compared with those equaled to or over 30 years old. There were no differences in hemodynamic profiles or the proportion of BMPR2 mutation carriers between groups according to sex.ConclusionThe prevalence of BMPR2 mutations in Korean IPAH patients was 22%. Mutation carriers were younger and had a poorer hemodynamic profile compared with the non-carriers.Clinical trial registrationClinicaltrials.gov NCT01054105

Targeting translational read-through of premature termination mutations in BMPR2 with PTC124 for pulmonary arterial hypertension.

Pulmonary arterial hypertension is a fatal disorder of the lung circulation in which accumulation of vascular cells progressively obliterates the pulmonary arterioles. This results in sustained elevation in pulmonary artery pressure leading eventually to right heart failure. Approximately, 80% of familial and 20% of sporadic idiopathic pulmonary arterial hypertension cases are caused by mutations in the bone morphogenetic protein receptor type 2 (BMPR2). Nonsense mutations in BMPR2 are amongst the most common mutations found, where the insertion of a premature termination codon causes mRNA degradation via activation of the nonsense-mediated decay pathway leading to a state of haploinsufficiency. Ataluren (PTC124), a compound that permits ribosomal read-through of premature stop codons, has been previously reported to increase BMPR2 protein expression in cells derived from pulmonary arterial hypertension patients harbouring nonsense mutations. In this study, we characterised the effects of PTC124 on a range of nonsense BMPR2 mutations, focusing on the R584X mutation both in vitro and in vivo. Treatment with PTC124 partially restored BMPR2 protein expression in blood outgrowth endothelial cells isolated from a patient harbouring the R584X mutation. Furthermore, a downstream bone morphogenetic protein signalling target, Id1, was rescued by PTC124 treatment. Mutant cells also exhibited increased lipopolysaccharide-induced permeability, which was reversed by PTC124 treatment. Increased proliferation and apoptosis in R584X blood outgrowth endothelial cells were also significantly reduced by PTC124. Moreover, oral PTC124 increased lung BMPR2 protein expression in mice harbouring the R584X mutation (Bmpr2+/R584X). Our findings provide support for future experimental medicine studies of PTC124 in pulmonary arterial hypertension patients with specific nonsense BMPR2 mutations.

BMPR2 dysfunction impairs insulin signaling and glucose homeostasis in cardiomyocytes.

Insulin resistance and right ventricular (RV) dysfunction are associated with lipotoxicity in heritable forms of pulmonary arterial hypertension (PAH), commonly due to mutations in bone morphogenetic protein receptor type 2 (BMPR2). How BMPR2 dysfunction in cardiomyocytes alters glucose metabolism and the response of these cells to insulin are unknown. We hypothesized that BMPR2 mutation in cardiomyocytes alters glucose-supported mitochondrial respiration and impairs cellular responses to insulin, including glucose and lipid uptake. We performed metabolic assays, immunofluorescence and Western analysis, RNA profiling, and radioactive isotope uptake studies in H9c2 cardiomyocyte cell lines with and without patient-derived BMPR2 mutations (mutant cells), with and without insulin. Unlike control cells, BMPR2 mutant cardiomyocytes have reduced metabolic plasticity as indicated by reduced mitochondrial respiration with increased mitochondrial superoxide production. These mutant cells show enhanced baseline phosphorylation of insulin-signaling protein as indicated by increased Akt, AMPK, and acetyl-CoA carboxylase phosphorylation that may negatively influence fatty acid oxidation and enhance lipid uptake, and are insulin insensitive. Furthermore, mutant cells demonstrate an increase in milk fat globule-EGF factor-8 protein (MFGE8), which influences the insulin-signaling pathway by phosphorylating AktSer473 via phosphatidylinositol 3-kinase and mammalian target of rapamycin. In conclusion, BMPR2 mutant cardiomyocytes have reduced metabolic plasticity and fail to respond to glucose. These cells have enhanced baseline insulin-signaling pattern favoring insulin resistance with failure to augment this pattern in response to insulin. BMPR2 mutation possibly blunts glucose uptake and enhances lipid uptake in these cardiomyocytes. The MFGE8-driven signaling pathway may suggest a new mechanism underlying RV lipotoxicity in PAH.

Genetic linkage analysis of a large family identifies FIGN as a candidate modulator of reduced penetrance in heritable pulmonary arterial hypertension

BackgroundMapping the genetic component of molecular mechanisms responsible for the reduced penetrance (RP) of rare disorders constitutes one of the most challenging problems in human genetics. Heritable pulmonary arterial hypertension...

FHIT, a Novel Modifier Gene in Pulmonary Arterial Hypertension.

Pulmonary arterial hypertension (PAH) is characterized by progressive narrowing of pulmonary arteries, resulting in right heart failure and death. BMPR2 (bone morphogenetic protein receptor type 2) mutations account for most familial PAH forms whereas reduced BMPR2 is present in many idiopathic PAH forms, suggesting dysfunctional BMPR2 signaling to be a key feature of PAH. Modulating BMPR2 signaling is therapeutically promising, yet how BMPR2 is downregulated in PAH is unclear. We intended to identify and pharmaceutically target BMPR2 modifier genes to improve PAH. We combined siRNA high-throughput screening of >20,000 genes with a multicohort analysis of publicly available PAH RNA expression data to identify clinically relevant BMPR2 modifiers. After confirming gene dysregulation in tissue from patients with PAH, we determined the functional roles of BMPR2 modifiers in vitro and tested the repurposed drug enzastaurin for its propensity to improve experimental pulmonary hypertension (PH). We discovered FHIT (fragile histidine triad) as a novel BMPR2 modifier. BMPR2 and FHIT expression were reduced in patients with PAH. FHIT reductions were associated with endothelial and smooth muscle cell dysfunction, rescued by enzastaurin through a dual mechanism: upregulation of FHIT as well as miR17-5 repression. Fhit-/- mice had exaggerated hypoxic PH and failed to recover in normoxia. Enzastaurin reversed PH in the Sugen5416/hypoxia/normoxia rat model, by improving right ventricular systolic pressure, right ventricular hypertrophy, cardiac fibrosis, and vascular remodeling. This study highlights the importance of the novel BMPR2 modifier FHIT in PH and the clinical value of the repurposed drug enzastaurin as a potential novel therapeutic strategy to improve PAH.

Whole-exome sequencing improves genetic testing accuracy in pulmonary artery hypertension.

Sanger sequencing, the traditional “gold standard” for mutation detection, has been wildly used in genetic testing of pulmonary artery hypertension (PAH). However, with the advent of whole-exome sequencing (WES), few studies have compared the accuracy of WES and Sanger sequencing in routine genetic testing of PAH. PAH individuals were enrolled from Fu Wai Hospital and Shanghai Pulmonary Hospital. WES was used to analyze DNA samples from 120 PAH patients whose bone morphogenetic protein receptor type 2 (BMPR2) mutation statuses had been previously studied using Sanger sequencing. The Sanger sequencing and WES agreement was 98.3% (118/120) with near-perfect agreement (κ coefficient = 0.848). There was no significant difference between the two methods on the McNemar–Bowker test (P > 0.05). Twenty-one BMPR2 mutation carriers and 99 non-carriers were detected by Sanger sequencing. Among the 21 BMPR2 carriers detected by Sanger sequencing, one variant (c.1040 T > A) was not found by WES. Among the 99 BMPR2 non-carriers, WES detected an extra mutation carrier (c.76 + 1 G > C) missed by Sanger sequencing. Both false-positive and false-negative results were highly conserved and were re-analyzed by Sanger sequencing. WES improved the accuracy of Sanger sequencing and detected 1% (1/99) false-positive and 4.8% (1/21) false-negative results of Sanger sequencing. No false-positive and false-negative results of WES were identified in our analysis. WES is non-inferior to Sanger sequencing and may play a more important role in genetic testing of PAH patients in the future.

Modulation of Endothelial Bone Morphogenetic Protein Receptor Type 2 Activity by Vascular Endothelial Growth Factor Receptor 3 in Pulmonary Arterial Hypertension.

Bone morphogenetic protein (BMP) signaling has multiple roles in the development and function of the blood vessels. In humans, mutations in BMP receptor type 2 (BMPR2), a key component of BMP signaling, have been identified in the majority of patients with familial pulmonary arterial hypertension (PAH). However, only a small subset of individuals with BMPR2 mutation develops PAH, suggesting that additional modifiers of BMPR2 function play an important role in the onset and progression of PAH. We used a combination of studies in zebrafish embryos and genetically engineered mice lacking endothelial expression of Vegfr3 to determine the interaction between vascular endothelial growth factor receptor 3 (VEGFR3) and BMPR2. Additional in vitro studies were performed by using human endothelial cells, including primary lung endothelial cells from subjects with PAH. Attenuation of Vegfr3 in zebrafish embryos abrogated Bmp2b-induced ectopic angiogenesis. Endothelial cells with disrupted VEGFR3 expression failed to respond to exogenous BMP stimulation. Mechanistically, VEGFR3 is physically associated with BMPR2 and facilitates ligand-induced endocytosis of BMPR2 to promote phosphorylation of SMADs and transcription of ID genes. Conditional, endothelial-specific deletion of Vegfr3 in mice resulted in impaired BMP signaling responses, and significantly worsened hypoxia-induced pulmonary hypertension. Consistent with these data, we found significant decrease in VEGFR3 expression in pulmonary arterial endothelial cells from human PAH subjects, and reconstitution of VEGFR3 expression in PAH pulmonary arterial endothelial cells restored BMP signaling responses. Our findings identify VEGFR3 as a key regulator of endothelial BMPR2 signaling and a potential determinant of PAH penetrance in humans.

Profiling nitric oxide metabolites in patients with idiopathic pulmonary arterial hypertension.

Intact nitric oxide (NO) signalling is critical to maintaining appropriate pulmonary vascular tone. NO bioavailability is reduced in patients with pulmonary arterial hypertension. This study aimed to examine the impact of NO plasma metabolites (NOx) relative to haemodynamic dysfunction and mortality in patients with idiopathic pulmonary arterial hypertension (IPAH).A total of 104 consecutive adult IPAH patients who had undergone genetic counselling when first diagnosed were enrolled in this prospective study.The median concentration of NOx (μmol·L-1) was significantly lower in IPAH patients compared with healthy subjects, and was decreased further in 19 carriers of the bone morphogenetic protein-receptor type-2 (BMPR2) mutation compared to non-carriers. Reduced concentrations of NOx were correlated with mean pulmonary arterial pressure (mPAP), pulmonary vascular resistance (PVR) and cardiac output. Compared with higher baseline NOx concentrations, patients with a NOx concentration of ≤10 μmol·L-1 had a markedly worse survival. After adjustment for clinical features, a BMPR2 mutation and haemodynamics, a lower NOx level remained an increased risk of mortality.Patients with IPAH had lower levels of plasma NOx, which correlated inversely with mPAP, PVR and survival. Plasma NOx may be an important biomarker and prognostic indicator, suggesting that reduced NO synthesis contributes to the pathogenesis of IPAH.

Mechanisms of Lipid Accumulation in the Bone Morphogenetic Protein Receptor Type 2 Mutant Right Ventricle.

In heritable pulmonary arterial hypertension with germline mutation in the bone morphogenetic protein receptor type 2 (BMPR2) gene, right ventricle (RV) dysfunction is associated with RV lipotoxicity; however, the underlying mechanism for lipid accumulation is not known. We hypothesized that lipid accumulation in cardiomyocytes with BMPR2 mutation occurs owing to alterations in lipid transport and impaired fatty acid oxidation (FAO), which is exacerbated by a high-lipid (Western) diet (WD). We used a transgenic mouse model of pulmonary arterial hypertension with mutant BMPR2 and generated a cardiomyocyte cell line with BMPR2 mutation. Electron microscopy and metabolomic analysis were performed on mouse RVs. By metabolomics analysis, we found an increase in long-chain fatty acids in BMPR2 mutant mouse RVs compared with controls, which correlated with cardiac index. BMPR2-mutant cardiomyocytes had increased lipid compared with controls. Direct measurement of FAO in the WD-fed BMPR2-mutant RV showed impaired palmitate-linked oxygen consumption, and metabolomics analysis showed reduced indices of FAO. Using both mutant BMPR2 mouse RVs and cardiomyocytes, we found an increase in the uptake of (14)C-palmitate and fatty acid transporter CD36 that was further exacerbated by WD. Taken together, our data suggest that impaired FAO and increased expression of the lipid transporter CD36 are key mechanisms underlying lipid deposition in the BMPR2-mutant RV, which are exacerbated in the presence of dietary lipids. These findings suggest important features leading to RV lipotoxicity in pulmonary arterial hypertension and may point to novel areas of therapeutic intervention.

Sequencing of mutations in the serine/threonine kinase domain of the bone morphogenetic protein receptor type 2 gene causing pulmonary arterial hypertension.

Objective:Germline mutations in the bone morphogenetic protein receptor type-2 (BMPR2) gene are considered to be a major risk factor for pulmonary arterial hypertension (PAH). BMPR2 mutations have been reported in 10%–20% of idiopathic PAH and in 80% of familial PAH cases. The aim of this study was to evaluate the frequency of mutations in the serine/threonine kinase domain of the BMPR2 gene in a group of patients from a single PAH referral center in Turkey.Methods:This cross-sectional study used a DNA-sequencing method to investigate BMPR2 mutations in the serine-threonine-kinase domain in 43 patients diagnosed with PAH [8 with idiopathic PAH and 35 with congenital heart disease (CHD)] from a single PAH referral center. Patients were included if they had a hemodynamically measured mean pulmonary arterial pressure of >25 mm Hg with a mean pulmonary capillary wedge pressure of ≤15 mm Hg. Patients with severe left heart disease and/or pulmonary disease that could cause pulmonary hypertension were excluded. Associations between categoric variables were determined using the chi-square test. Differences between idiopathic and CHD-associated PAH groups were compared with the unpaired Student’s t-test for continuous variables.Results:We detected a missense mutation, [p.C347Y (c.1040G>A)], in one patient with idiopathic PAH in exon 8 of the BMPR2 gene. The mutation was detected in a 27-year-old female with a remarkable family history for PAH. She had a favorable response to endothelin receptor antagonists. No mutations were detected in the exons 5–11 of the BMPR2 gene in the PAH-CHD group.Conclusion:A missense mutation was detected in only one of the eight patients with idiopathic PAH. The BMPR2 missense mutation rate of 12.5% in this cohort of Turkish patients with idiopathic PAH was similar to that seen in European registries. The index patient was a young female with a family history remarkable for PAH; she had a good long-term response to PAH-specific treatment, probably due to the early initiation of the treatment. Genetic screening of families affected by PAH might have great value in identifying the disease at an early stage.

A comparative histological study of pulmonary vascular lesions in lungs of patients with idiopathic or heritable PAH

Rationale Although patients with pulmonary arterial hypertension (PAH) carrying a bone morphogenetic protein receptor type 2 (BMPR2) mutation present approximately 10 years earlier than noncarriers and have a more severe hemodynamic compromise at diagnosis, their histological features have never been investigated in detail and compared with noncarriers. Objective The aim of this study was to explore and compare the histology and morphology of pulmonary vascular lesions between BMPR2 mutation carriers and noncarriers. Methods and results Five random sections of lung parenchyma from 27 PAH patients, including 15 BMPR2 mutation carriers and 12 noncarriers, have been histological reevaluated blindly by two experienced pathologists. Plexiform lesions (Pls) density (n/cm2), inflammation score and arterial thickening were evaluated in the two patient groups. We found a positive trend of Pls density in BMPR2 mutation carriers as compared to noncarriers. We found no difference in the artery inflammation evaluated according to a semiquantitative score system. There was also no difference in the arterial thickening (i.e. intimal, medial and total wall thickening) evaluated in 5 transversal artery sections using the Nikon NIS-Elements morphometrical software. Bronchial artery thickening was evaluated by measuring the bronchial artery surface and by comparing it to the bronchial surface (bronchial artery surface/bronchus surface). Major bronchial artery thickening was associated with BMPR2 mutation status. It is noteworthy that most patients with a high bronchial artery surface/bronchus surface ratio presented haemoptysis. In addition, bronchial microvascularization evaluated by immunohistochemistry evidenced a much more prominent bronchial capillary network in BMPR2 mutated group. We noticed also that “atypical Pls” (histologically identified as larger angiodysplastic and fibrotic lesions) have almost exclusively been found in the group of BMPR2 mutation carriers. Conclusion Our results reveal, for the first time, distinctive morphologic patterns between lungs of patients with BMPR2 mutation carriers and noncarriers. A better knowledge of these specific histological features will lead to a better understanding of the PAH pathogenesis.

De novo mutations in the BMPR2 gene in patients with heritable pulmonary arterial hypertension.

A substantial proportion of patients with pulmonary arterial hypertension (PAH) have mutations in the Bone Morphogenetic Protein Receptor type-2 (BMPR2) gene. PAH due to BMPR2 mutations is inherited as an autosomal dominant trait with several unique features, including a wide variety of mutations, reduced penetrance, a skewed gender ratio, variable expressivity and genetic anticipation. To address the genetic background of these unique features of BMPR2 mutation, we conducted a systematic analysis of 15 PAH families with BMPR2 mutation. The exonic protein coding sequence of BMPR2 was amplified by polymerase chain reaction and the products were sequenced directly to detect point mutations in BMPR2. Parental identification was carried out to confirm the parental relationship using multiplex 15 loci analysis. Combining mutation detection in family members with parental identification, we described three cases of de novo mutation in the BMPR2 gene by different modes in a PAH family. These de novo mutations may account for the wide variety of mutations in BMPR2. Taken together with the juvenile onset of the disease, there is possibly some balance of de novo mutations and untransmittable mutations which keeps the frequency of PAH low in the general population.

Functional changes in pulmonary arterial endothelial cells associated with BMPR2 mutations.

Pulmonary arterial hypertension (PAH) is a devastating disease characterized by abnormal remodeling of small, peripheral pulmonary arteries. Germline mutations in the bone morphogenetic protein receptor type 2 (BMPR2) gene are a major risk factor for developing PAH. At present, the correlation between the BMPR2 mutation and the patient's prognosis remains controversial despite several investigations. In this study, we explored the functional effects of four BMPR2 mutations to dissect the functional significance of the BMPR2 gene defect. Cellular immunofluorescence assay of four mutants (Tyr67Cys, Thr268fs, Ser863Asn, and Gln433X) revealed that the BMPR2 protein containing Thr268fs, Ser863Asn, or Gln433X exhibited abnormal subcellular localization. The BrdU incorporation and TUNEL assay suggested that any of the BMPR2 mutations Thr268fs, Ser863Asn, or Gln433X could improve endothelial cell apoptosis and decrease cell proliferation. All of the four mutants could inhibit nitric oxide (NO) synthesis in HLMVE cells, and ET-1 levels increased in the cells transfected with mutant Ser863Asn. Our results will improve the understanding of the genotype-phenotype correlations and mechanisms associated with BMPR2 mutations.

Early onset severe pulmonary arterial hypertension with ‘two-hit’ digenic mutations in both BMPR2 and KCNA5 genes

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by elevated mean pulmonary artery pressure (mPAp) greater than 25 mm Hg at rest in the setting of a normal or mildly elevated left heart filling pressures [ [1] Hoeper M.M. Bogaard H.J. Condliffe R. et al. Definitions and diagnosis of pulmonary hypertension. J Am Coll Cardiol. 2013; 62 ([Suppl.]): D42-D50 Crossref PubMed Scopus (1227) Google Scholar ]. Various factors such as genetic mutations, inflammation/infection, drugs/toxins, abnormal metabolism, and altered hemodynamics have been reported in the molecular pathogenesis of PAH [ [2] Rabinovitch M. Molecular pathogenesis of pulmonary arterial hypertension. J Clin Invest. 2012; 122: 4306-4313 Crossref PubMed Scopus (467) Google Scholar ]. Among them, genetic predisposition caused by heterogeneous germline mutations of the BMPR2 (bone morphogenetic protein receptor type 2, a member of the TGFβ signaling pathway) gene has been found to be accountable for 75% of heritable PAH (HPAH) and 25% idiopathic PAH (IPAH), respectively [ [3] Soubrier F. Chung W.K. Machado R. et al. Genetics and genomics of pulmonary arterial hypertension. J Am Coll Cardiol. 2013; 62: D13-D21 Crossref PubMed Scopus (229) Google Scholar ]. Other partners in the TGF-β signaling pathways, such as ACRL1 (activin receptor-like kinase type 1), ENG (endoglin), SMAD8, and SMAD4 genes, are also reported to be involved in the PAH pathogenesis [ [3] Soubrier F. Chung W.K. Machado R. et al. Genetics and genomics of pulmonary arterial hypertension. J Am Coll Cardiol. 2013; 62: D13-D21 Crossref PubMed Scopus (229) Google Scholar ]. The pore-forming subunit, Kv1.5, forms functional voltage-gated potassium (Kv) channels in human pulmonary artery smooth muscle cells (PASMC) and abnormal potassium channel Kv1.5 function encoded by KCNA5 mutations has been previously reported in patients with IPAH [ [4] Remillard C.V. Tigno D.D. Platoshyn O. et al. Function of Kv1.5 channels and genetic variations of KCNA5 in patients with idiopathic pulmonary arterial hypertension. Am J Physiol Cell Physiol. 2007; 292: C1837-C1853 Crossref PubMed Scopus (128) Google Scholar ]. Other genes such as CAV1, BMP9/GDF2 and KCNK3 have also been described in association with both HPAH and IPAH [ [3] Soubrier F. Chung W.K. Machado R. et al. Genetics and genomics of pulmonary arterial hypertension. J Am Coll Cardiol. 2013; 62: D13-D21 Crossref PubMed Scopus (229) Google Scholar ].

Pulmonary arterial hypertension preceding idiopathic pulmonary fibrosis in a BMPR2 mutation positive patient

To the Editor: When pulmonary hypertension (PH) develops in a patient with idiopathic pulmonary fibrosis (IPF) it is usually categorised in World Health Organization (WHO) group III: PH associated with chronic lung disease and/or hypoxia [1]. Given the fact that pulmonary arterial hypertension (PAH) (WHO group I) and IPF are both rare and fatal diseases, their manifestation in a single patient is unlikely to occur by chance. Here, we describe for the first time the concurrent development of IPF and PH in a patient with a bone morphogenetic protein receptor type 2 ( BMPR2) mutation. An 80-year-old female presented with fever, chills, shortness of breath, chest pain and a decline in exercise tolerance. She had been diagnosed 3 years before with hereditary PAH (HPAH) associated with a BMPR2 mutation (c.637C>T; p.Arg213X (reference sequence NM_001204)), for which she received ambrisentan, sildenafil and diuretic treatment. Right heart catheterisation at the time of HPAH diagnosis had shown a mean pulmonary artery pressure of 42 mmHg and a pulmonary arterial wedge pressure of 2 mmHg. Pulmonary function tests had shown a vital capacity of 2.7 L (139%) and a forced expiratory volume in 1 s of 2.3 L (144%). She was a former smoker and denied the …

Bone morphogenetic protein receptor type 2 mutations, clinical phenotypes and outcomes of Japanese patients with sporadic or familial pulmonary hypertension

Mutation of bone morphogenetic protein receptor type 2 (BMPR2) is a cause of pulmonary arterial hypertension (PAH). We measured the prevalence of this mutation and its impact on the phenotypes and long-term clinical outcomes in Japanese patients. Between 1999 and 2007, we consecutively enrolled and, until March 2012, followed 49 Japanese patients with PAH, including nine familial cases from seven families. We genotyped BMPR2, using direct sequencing and multiplex ligation-dependent probe amplification, to examine (i) the prevalence of BMPR2 mutations and gene rearrangement, (ii) the relationship between BMPR2 genotype and clinical phenotypes, and (iii) the long-term clinical outcomes of mutation carriers versus non-carriers under state-of-the-art medical therapy. BMPR2 mutations were present in four of the seven families (57%) and in 14 of the 40 patients (35%) with sporadic PAH. The mean age at onset of PAH was 37.4 years in BMPR2 carriers, versus 25.9 years in non-carriers (P = 0.0025). The gender distribution and hemodynamic status at time of diagnosis were similar regardless of the mutation status. The 5-year survival rate after diagnosis of PAH was 88.5% in BMPR2 mutation carriers versus 80.9% in non-carriers (ns). The prevalence of BMPR2 mutations in Japanese with PAH was similar to that reported in other populations. At onset of PAH, BMPR2 mutation non-carriers were, on average, younger than carriers, possibly due to the heterogeneity of this subpopulation. With state-of-the-art therapy, the long-term survival of patients with PAH was high, regardless of the mutation status.