Complex inheritance in Pulmonary Arterial Hypertension patients with several mutations

The prevalence of pathogenic variants in the BMPR2 gene in patients with the idiopathic pulmonary arterial hypertension in the Russian population: sequencing data and meta-analysis

BACKGROUND

Idiopathic pulmonary arterial hypertension (IPAH) is a rare and severe form of pulmonary hypertension, with a genetic basis most commonly associated with mutations in the BMPR2 gene. However, no genetic testing has been reported for IPAH patients in the Russian population, nor have systematic studies been conducted to assess the frequency of pathogenic variants in this group.

METHODS

The study cohort included 105 IPAH patients, consisting of 23 males and 82 females, who were managed at the PH care center in Moscow, Russia, from 2014 to 2024. Genetic testing was performed using whole-genome sequencing. Variant identification and annotation were conducted using GATK, DeepVariant, VEP, sv-callers and AnnotSV. A meta-analysis, performed with MOOSE, included 24 studies involving 3124 IPAH patients and 470 P/LP variants. Pathogenicity reassessment was carried out using InterVar, which incorporates ACMG criteria.

RESULTS

Analysis of 105 adult IPAH patients in Russia revealed 11 patients (10.48%) as carriers of pathogenic or likely pathogenetic (P/LP) BMPR2 variants. As the result of reassessment, the number of P/LP BMPR2 variants raised from 394 (59%) to 445 (67%) with 80 pathogenic variants became of uncertain significance, and 152 unclassified variants became P/LP. The meta-analysis of these reevaluated pathogenic variants showed that while the frequency of P/LP variants in our cohort (10.48%) is lower than the overall average of 17.75% from the meta-analysis, the difference is not statistically significant (p = 0.062). Additionally, we report three P/LP BMPR2 variants, not reported in literature, with one being structural, and four P/LP variants in TBX4, ATP13A3 and AQP1 genes from 27 IPAH genes in 3 patients.

CONCLUSIONS

For the first time, we present the results of genetic testing in IPAH patients from the Russian population. Despite the considerable heterogeneity in the world-wide data, the prevalence of pathogenic BMPR2 mutations in IPAH patients from the Russian population does not significantly differ from the overall average in the meta-analysis. It is crucial to periodically reassess the pathogenicity of published variants, as half of the pathogenic BMPR2 IPAH variants were reclassified as LP or of uncertain significance.

Idiopathic and connective tissue disease-associated pulmonary arterial hypertension (PAH): Similarities, differences and the role of autoimmunity

Pre-capillary pulmonary arterial hypertension (PAH) is hemodynamically characterized by a mean pulmonary arterial pressure (mPAP) ≥ 20 mmHg, pulmonary capillary wedge pressure (PAWP) ≤15 mmHg and pulmonary vascular resistance (PVR) > 2. PAH is classified in six clinical subgroups, including idiopathic PAH (IPAH) and PAH associated to connective tissue diseases (CTD-PAH), that will be the main object of this review. The aim is to compare these two PAH subgroups in terms of epidemiology, histological and pathogenic findings in an attempt to define disease-specific features, including autoimmunity, that may explain the heterogeneity of response to therapy between IPAH and CTD-PAH.

Computed tomographic findings in TBX4 mutation: a common cause of severe pulmonary artery hypertension in children

BACKGROUND

Mutations in the T-Box 4 (TBX4) gene are a lesser-known cause of heritable pulmonary arterial hypertension (PAH). Patients with heritable PAH typically have worse outcomes when compared with patients with idiopathic PAH, yet little is known about the phenotypical presentation of this mutation.

OBJECTIVE

This article reviews the pattern of chest CT findings in pediatric patients with PAH and TBX4 mutations and compares their radiographic presentation with those of age-matched patients with PAH but without TBX4 mutations.

MATERIALS AND METHODS

A retrospective chart review of the pulmonary arterial hypertension database was performed. Pediatric patients with PAH-confirmed TBX4 mutations and an available high CT were included. Fifteen (9 females) patients met the inclusion criteria. Fourteen (8 females) age-matched controls with diagnosed PAH but without TBX4 mutations were also evaluated. The median age at diagnosis was 7.4 years (range: 0.1-16.4 years). Demographic information and clinical outcomes were collected. CTs of the chest were reviewed for multiple airway, parenchymal, and structural abnormalities (16 imaging findings in total). Chi-square tests were used to compare the prevalence of each imaging finding in the TBX4 cohort compared to the control group.

RESULTS

Patients with TBX-4 mutations had increased presence of peripheral or subpleural irregularity (73% vs 0%, P < 0.01), cystic lucencies (67% vs 7%, P < 0.01), and linear or reticular opacity (53% vs 0%, P < 0.01) compared to the control group. Ground glass opacities, bronchiectasis, and centrilobular nodules were not significantly different between the two patient groups (P > 0.05).

CONCLUSION

TBX4 mutations have distinct imaging phenotypes in pediatric patients with PAH. Compared to patients without this mutation, patients with TBX-4 genes typically present with peripheral or subpleural irregularity, cystic lucencies, and linear or reticular opacity.

Ion channels as convergence points in the pathology of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a fatal disease of the cardiopulmonary system that lacks curative treatments. The main pathological event in PAH is elevated vascular resistance in the pulmonary circulation, caused by abnormal vasoconstriction and vascular remodelling. Ion channels are key determinants of vascular smooth muscle tone and homeostasis, and four PAH channelopathies (KCNK3, ABCC8, KCNA5, TRPC6) have been identified so far. However, the contribution of ion channels in other forms of PAH, which account for the majority of PAH patients, has been less well characterised. Here we reason that a variety of triggers of PAH (e.g. BMPR2 mutations, hypoxia, anorectic drugs) that impact channel function may contribute to the onset of the disease. We review the molecular mechanisms by which these ‘extrinsic’ factors converge on ion channels and provoke their dysregulation to promote the development of PAH. Ion channels of the pulmonary vasculature are therefore promising therapeutic targets because of the modulation they provide to both vasomotor tone and proliferation of arterial smooth muscle cells.

Identifying Potential Mutations Responsible for Cases of Pulmonary Arterial Hypertension

Pulmonary Arterial Hypertension (PAH) is a progressive and devastating disease for which there is an escalating body of genetic and related pathophysiological information on disease pathobiology. Nevertheless, the success to date in identifying susceptibility genes, genetic variants and epigenetic processes has been limited due to PAH clinical multi-faceted variations. A number of germline gene candidates have been proposed but demonstrating consistently the association with PAH has been problematic, at least partly due to the reduced penetrance and variable expressivity. Although the data for bone morphogenetic protein receptor type 2 (BMPR2) and related genes remains undoubtedly the most extensive, recent advanced gene sequencing technologies have facilitated the discovery of further gene candidates with mutations among those with and without familial forms of PAH. An in depth understanding of the multitude of biologic variations associated with PAH may provide novel opportunities for therapeutic intervention in the coming years. This knowledge will irrevocably provide the opportunity for improved patient and family counseling as well as improved PAH diagnosis, risk assessment, and personalized treatment.

Customized Massive Parallel Sequencing Panel for Diagnosis of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension is a very infrequent disease, with a variable etiology and clinical expressivity, making sometimes the clinical diagnosis a challenge. Current classification based on clinical features does not reflect the underlying molecular profiling of these groups. The advance in massive parallel sequencing in PAH has allowed for the describing of several new causative and susceptibility genes related to PAH, improving overall patient diagnosis. In order to address the molecular diagnosis of patients with PAH we designed, validated, and routinely applied a custom panel including 21 genes. Three hundred patients from the National Spanish PAH Registry (REHAP) were included in the analysis. A custom script was developed to annotate and filter the variants. Variant classification was performed according to the ACMG guidelines. Pathogenic and likely pathogenic variants have been found in 15% of the patients with 12% of variants of unknown significance (VUS). We have found variants in patients with connective tissue disease (CTD) and congenital heart disease (CHD). In addition, in a small proportion of patients (1.75%), we observed a possible digenic mode of inheritance. These results stand out the importance of the genetic testing of patients with associated forms of PAH (i.e., CHD and CTD) additionally to the classical IPAH and HPAH forms. Molecular confirmation of the clinical presumptive diagnosis is required in cases with a high clinical overlapping to carry out proper management and follow up of the individuals with the disease.

Pulmonary arterial hypertension associated with protein kinase inhibitors: a pharmacovigilance-pharmacodynamic study

The pathophysiology of pulmonary arterial hypertension (PAH) induced by protein kinase inhibitors (PKIs) remains unclear. To gain knowledge into this rare and severe pathology we performed a study combining a pharmacovigilance approach and the pharmacodynamic properties of PKIs.A disproportionality analysis on the World Health Organization pharmacovigilance database VigiBase using the reporting odds ratio (ROR) and 95% confidence interval was first performed. Then, we identified the most relevant cellular targets of interest through a systematic literature review and correlated the pharmacovigilance signals with the affinity for the different PKIs. We further performed a hierarchical cluster analysis to assess patterns of binding affinity.A positive disproportionality signal was found for dasatinib, bosutinib, ponatinib, ruxolitinib and nilotinib. Five non-receptor protein kinases significantly correlate with disproportionality signals: c-Src (r=0.79, p=0.00027), c-Yes (r=0.82, p=0.00015), Lck (r=0.81, p=0.00046) and Lyn (r=0.80, p=0.00036), all belonging to the Src protein kinase family, and TEC (r=0.85, p=0.00006). Kinases of the bone morphogenetic protein signalling pathway also seem to play a role in the pathophysiology of PKI-induced PAH. Interestingly, the dasatinib affinity profile seems to be different from that of other PKIs in the cluster analysis.The study highlights the potential role of the Src protein kinase family and TEC in PAH induced by PKIs. This approach combining pharmacovigilance and pharmacodynamics data allowed us to generate some hypotheses about the pathophysiology of the disease; however, the results have to be confirmed by further studies.

Pulmonary arterial hypertension associated to systemic erythematosus lupus: molecular characterization of 3 cases

BACKGROUND AND OBJECTIVE

Pulmonary arterial hypertension associated with systemic lupus erythematosus (PAH-SLE) is a rare disease with a low incidence rate. In this study, PAH related genes and genetic modifiers were characterised molecularly in patients with PAH-SLE.

PATIENTS AND METHODS

Three patients diagnosed with PAH-SLE and 100 control individuals were analysed after signing an informed consent.

RESULTS

Two out of the three analysed patients with PAH-SLE were carriers of pathogenic mutations in the genes BMPR2 and ENG. After an in silico analysis, pathogenic mutations were searched for in control individuals and different databases, with negative results, and they were thus functionally analysed. The third patients only showed polymorphisms in the genes BMPR2, ACVRL1 and ENG. Several genetic variants and genetic modifiers were identified in the three analysed patients. These modifiers, along with the pathogenic mutations, could lead to a more severe clinical course in patients with PAH.

CONCLUSIONS

We present, for the first time, patients with PAH-SLE carrying pathogenic mutations in the main genes related to PAH and alterations in the genetic modifiers.

Factors Associated with Heritable Pulmonary Arterial Hypertension Exert Convergent Actions on the miR-130/301-Vascular Matrix Feedback Loop

Pulmonary arterial hypertension (PAH) is characterized by occlusion of lung arterioles, leading to marked increases in pulmonary vascular resistance. Although heritable forms of PAH are known to be driven by genetic mutations that share some commonality of function, the extent to which these effectors converge to regulate shared processes in this disease is unknown. We have causally connected extracellular matrix (ECM) remodeling and mechanotransduction to the miR-130/301 family in a feedback loop that drives vascular activation and downstream PAH. However, the molecular interconnections between factors genetically associated with PAH and this mechano-driven feedback loop remain undefined. We performed systematic manipulation of matrix stiffness, the miR-130/301 family, and factors genetically associated with PAH in primary human pulmonary arterial cells and assessed downstream and reciprocal consequences on their expression. We found that a network of factors linked to heritable PAH converges upon the matrix stiffening-miR-130/301-PPARγ-LRP8 axis in order to remodel the ECM. Furthermore, we leveraged a computational network biology approach to predict a number of additional molecular circuits functionally linking this axis to the ECM. These results demonstrate that multiple genes associated with heritable PAH converge to control the miR-130/301 circuit, triggering a self-amplifying feedback process central to pulmonary vascular stiffening and disease.

Molecular and functional characterization of the BMPR2 gene in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension is a progressive disease that causes the obstruction of precapillary pulmonary arteries and a sustained increase in pulmonary vascular resistance. The aim was to analyze functionally the variants found in the BMPR2 gene and to establish a genotype-phenotype correlation. mRNA expression studies were performed using pSPL3 vector, studies of subcellular localization were performed using pEGFP-N1 vector and luciferase assays were performed using pGL3-Basic vector. We have identified 30 variants in the BMPR2 gene in 27 of 55 patients. In 16 patients we detected pathogenic mutations. Minigene assays revealed that 6 variants (synonymous, missense) result in splicing defect. By immunofluorescence assay, we observed that 4 mutations affect the protein localization. Finally, 4 mutations located in the 5'UTR region showed a decreased transcriptional activity in luciferase assays. Genotype-phenotype correlation, revealed that patients with pathogenic mutations have a more severe phenotype (sPaP p = 0.042, 6MWT p = 0.041), a lower age at diagnosis (p = 0.040) and seemed to have worse response to phosphodiesterase-5-inhibitors (p = 0.010). Our study confirms that in vitro expression analysis is a suitable approach in order to investigate the phenotypic consequences of the nucleotide variants, especially in cases where the involved genes have a pattern of expression in tissues of difficult access.

Mutational screening in genes related with porto-pulmonary hypertension: An analysis of 6 cases

INTRODUCTION

Portopulmonary hypertension (PPH) is a rare disease with a low incidence and without a clearly-identified genetic component. The aim of this work was to check genes and genetic modifiers related to pulmonary arterial hypertension in patients with PPH in order to clarify the molecular basis of the pathology.

PATIENTS

We selected a total of 6 patients with PPH and amplified the exonic regions and intronic flanking regions of the relevant genes and regions of interest of the genetic modifiers.

RESULTS

Six patients diagnosed with PPH were analyzed and compared to 55 healthy individuals. Potentially-pathogenic mutations were identified in the analyzed genes of 5 patients. None of these mutations, which are highly conserved throughout evolution, were detected in the control patients nor different databases analyzed (1000 Genomes, ExAC and DECIPHER). After analyzing for genetic modifiers, we found different variations that could favor the onset of the disease.

CONCLUSIONS

The genetic analysis carried out in this small cohort of patients with PPH revealed a large number of mutations, with the ENG gene showing the greatest mutational frequency.

The role of genetics in pulmonary arterial hypertension

Group 1 pulmonary hypertension or pulmonary arterial hypertension (PAH) is a rare disease characterized by proliferation and occlusion of small pulmonary arterioles, leading to progressive elevation of pulmonary artery pressure and pulmonary vascular resistance, and right ventricular failure. Historically, it has been associated with a high mortality rate, although, over the last decade, treatment has improved survival. PAH includes idiopathic PAH (IPAH), heritable PAH (HPAH), and PAH associated with certain medical conditions. The aetiology of PAH is heterogeneous, and genetics play an important role in some cases. Mutations in BMPR2, encoding bone morphogenetic protein receptor 2, a member of the transforming growth factor-β superfamily of receptors, have been identified in 70% of cases of HPAH, and in 10-40% of cases of IPAH. Other genetic causes of PAH include mutations in the genes encoding activin receptor-like type 1, endoglin, SMAD9, caveolin 1, and potassium two-pore-domain channel subfamily K member 3. Mutations in the gene encoding T-box 4 have been identified in 10-30% of paediatric PAH patients, but rarely in adults with PAH. PAH in children is much more heterogeneous than in adults, and can be associated with several genetic syndromes, congenital heart disease, pulmonary disease, and vascular disease. In addition to rare mutations as a monogenic cause of HPAH, common variants in the gene encoding cerebellin 2 increase the risk of PAH by approximately two-fold. A PAH panel of genes is available for clinical testing, and should be considered for use in clinical management, especially for patients with a family history of PAH. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

EIF2AK4 mutation as "second hit" in hereditary pulmonary arterial hypertension

Background

Mutations in the eukaryotic translation initiation factor 2α kinase 4 (EIF2AK4) gene have recently been identified in recessively inherited veno-occlusive disease. In this study we assessed if EIF2AK4 mutations occur also in a family with autosomal dominantly inherited pulmonary arterial hypertension (HPAH) and incomplete penetrance of bone morphogenic protein receptor 2 (BMPR2) mutations.

Methods

Clinical examinations in a family with 10 members included physical examination, electrocardiogram, (stress)-echocardiography and lung function. Manifest PAH was confirmed by right heart catheterisation in three affected subjects. Genetic analysis was performed using a new PAH-specific gene panel analysis with next generation sequencing of all known PAH and further candidate genes. Identified variants were confirmed by Sanger sequencing.

Results

All living family members with manifest HPAH carried two pathogenic heterozygous mutations: a frame shift mutation in the BMPR2 gene and a novel splice site mutation in the EIF2AK4 gene. Two family members who carried the BMPR2 mutation only did not develop manifest HPAH.

Conclusions

This is the first study suggesting that EIF2AK4 can also contribute to autosomal dominantly inherited HPAH. Up to now it has only been identified in a recessive form of HPAH. Only those family members with a co-occurrence of two mutations developed manifest HPAH. Thus, the EIF2AK4 and BMRPR2 mutations support the “second hit” hypothesis explaining the variable penetrance of HPAH in this family. Hence, the assessment of all known PAH genes in families with a known mutation might assist in predictions about the clinical manifestation in so far non-affected mutation carriers.