Background -

Pulmonary hypertension (PH), defined by mean pulmonary artery pressure >20 mmHg, is a common physiologic manifestation of many diseases. Pulmonary arterial hypertension (PAH) represents a smaller subgroup of patients who have PH, and PAH causes significant cardiorespiratory morbidity and premature mortality. PH can manifest across the lifespan, with similar incidence for both pediatric- and adult-onset disease. However, pediatric-onset disease is particularly challenging because it is frequently associated with a more severe clinical course and comorbidities including lung and heart developmental anomalies. For PH Group 1/pulmonary arterial hypertension, causal genetic variants can be identified in ~13% of adults and ~43% of children.

Clinical implications –

Education about the option for genetic testing is strongly recommended for all pediatric and adult HPAH/IPAH patients. Both gene panel and exome/genome sequencing tests can be useful in diagnosis, but exome/genome sequencing provides a comprehensive dataset for reanalysis over time for cases without an initial diagnosis. Knowledge of genetic diagnoses can immediately impact clinical management of PH, including multimodal medical treatment, surgical intervention, transplantation decisions, and screening for associated conditions.

Conclusions -

There is a need for large, diverse, international consortia with ever-improving analytical pipelines to confirm previously implicated genes, identify additional genes/variants, assess penetrance, and clinically characterize each genetic subtype for natural history, prognosis and response to therapies to inform more precise clinical management.

Pulmonary hypertension (PH), defined by mean pulmonary artery pressure >20 mm Hg, is a common physiologic manifestation of many diseases. Pulmonary arterial hypertension (PAH) represents a smaller subgroup of patients who have PH, and PAH causes significant cardiorespiratory morbidity and premature mortality. PH can manifest across the lifespan with an estimated incidence of 28.7 cases/100 000 individuals/year and prevalence of 127.3 cases/100 000 individuals.1  The World Symposium on PH2  and World Health Organization1  define 5 main PH Groups, with the majority of adult cases classified as Group 2/left heart disease (34%) and childhood cases classified as Group 1/PAH (65%).1  The diseases are caused by genetic, epigenetic, and environmental factors, as well as gene x environment interactions wherein genetic contributions to disease risk are modified by environmental exposures. This review will focus on the genomics of PH. Most genetic studies to date have been carried out in cohorts of European-centric, adult-onset Group 1/PAH because of the accessibility of cases and relative homogeneity of heritable and idiopathic PAH compared to other subtypes. We highlight studies with increased diversity of PAH subtype, age of PAH onset, and genetic ancestry where applicable. Emerging data from genetic studies of pediatric-onset PH indicate that the genetic basis is different from that of adults. Thus, we also highlight differences between adult-onset PH and pediatric-onset PH.

Recent analyses of relatively large PAH cohorts have further defined the frequency of individuals with deleterious variants in established PAH risk genes and the variant types (Table 1).3,4 BMPR2 (bone morphogenetic protein receptor 2) mutations are observed in the majority of heritable PAH cases across genetic ancestries,37  but only 10% to 20% of previously classified idiopathic PAH (IPAH) cases, and rarely for PAH associated with other diseases (autoimmune connective tissue diseases, congenital heart disease [CHD], portopulmonary disease, and others) or PAH induced by diet and toxins.3 BMPR2 carriers have younger mean age of onset and are less responsive to vasodilators compared to noncarriers.3,8,9  The pathogenetic mechanism of BMPR2 variants in adult-onset disease is haploinsufficiency due to likely gene-disrupting (including stop-gain, frameshift, splicing, and exon deletion) variants. Among children with PAH, there is an enrichment of predicted deleterious missense variants, suggesting that dysfunctional BMPR2 may be more harmful than inactivation or deletion of a normal copy of the gene.3,10 ACVRL1 (activin A receptor type II-like 1) and ENG (endoglin), both encoding protein receptor components of the BMPR2 complex, contribute to ~0.85% of PAH cases,3  especially adult-onset PAH associated with hereditary hemorrhagic telangiectasia. Variants in SMAD9 (mothers against decapentaplegic 9), encoding a downstream signaling molecule, contribute rarely. The newest PAH causal gene identified in the TGF-β pathway is GDF2 (growth and differentiation factor 2), encoding BMP9, a circulating cytokine and ligand of coreceptor complex BMPR2/ACVRL1. Genome-wide significance was demonstrated in both European4  and Asian11  cohorts with replication in the PAH Biobank cohort.3  Similar to other PAH risk genes in the TGF-β pathway, the mode of inheritance was autosomal dominant. Variants in GDF2 contribute to ~1% of PAH (mostly IPAH) cases in European-enriched cohorts3,4  and more frequently in Chinese patients (~6.7%).11  Most of the PAH-associated GDF2 variants are missense variants, a variant type that could not be rigorously assessed in smaller-sized cohorts.

Table 1

Allele Frequencies and Associated Variant Types for PAH Causal Genes in the National Biological Sample and Data Repository for PAH (PAH Biobank, n = 2572 cases a ); 90% of Cases are Adult-Onset

Allele Frequencies and Associated Variant Types for PAH Causal Genes in the National Biological Sample and Data Repository for PAH (PAH Biobank, n = 2572 cases a ); 90% of Cases are Adult-Onset
Allele Frequencies and Associated Variant Types for PAH Causal Genes in the National Biological Sample and Data Repository for PAH (PAH Biobank, n = 2572 cases a ); 90% of Cases are Adult-Onset

Outside of the TGF-β/BMP pathway, channelopathy gene ABCC8 (ATP-binding cassette subfamily member 8) and transcription factor TBX4 (T-box transcription factor 4) are the most common causes of PAH, accounting for ~1% of cases each (Table 1). More than 40 ABCC8 missense variants have been reported for PAH cases with IPAH, heritable PAH, and PAH associated with other diseases,3,12,13  and at least some of the variants have demonstrated reduced channel function.12  While the genetic evidence for ABCC8 in PAH is well-documented, more experimental evidence is needed to elucidate the pathogenetic mechanism. TBX4 was originally identified as a PAH causal gene in a cohort of children with PAH, some of whom had contiguous gene deletions and a more complex phenotype including intellectual delay and/or structural heart defects.14,15  Subsequent studies revealed an enrichment of likely gene-disrupting and missense TBX4 variants in pediatric-onset PAH, primarily IPAH and PAH associated with CHD , with rare adult-onset cases caused by TBX4.3,6,16  Originally described as a determinant of pattern formation including limb development,17  the association of TBX4 with PAH, cardiac defects18,19  and, more recently, a variety of developmental lung disorders19,20  indicates an expanding role for TBX4 in development.

Other established PAH causal genes contribute importantly but rarely to PAH. Evidence for these genes stems from family studies with corroboration in additional sporadic cases or large cohort studies. Biallelic variants in EIF2AK4 (eukaryotic initiation translation factor) cause rare forms of PAH, once known as pulmonary veno-occlusive disease and pulmonary capillary hemangiomatosis, and now classified as PAH with overt features of venous/capillary involvement.21,22  Loss of function missense variants identified 2 channelopathy genes, KCNK3 (potassium two pore domain channel),2326  a regulator of pulmonary vascular tone, and CAV1 (caveolin-1),2729  encoding a structural and signaling component of lipid rafts abundant in pulmonary endothelial membranes. Variants in these channel genes are associated with heritable PAH and IPAH. More recently, exome sequencing of large cohorts identified variants in pro-angiogenic gene KDR (kinase insert domain receptor),22,30,31  developmental transcription factor SOX173,14,16,32  and channel gene ATP13A3 (ATPase 13A3).3,4 KDR is highly expressed in lung and encodes the receptor for vascular endothelial growth factor type 2. Vascular endothelial growth factor signaling plays an essential role in embryonic lung development and structural maintenance of adult lung.33  Loss of function variants in KDR are associated with low diffusion capacity for carbon monoxide in IPAH cases.30 

Recent associations of variants in aquaporin 1 (AQP1),4  fibulin-2 (FBLN2),31  gamma-glutamyl carboxylase (GGCX),3  kallikrein 1 (KLK1),3  and platelet-derived growth factor D (PDGFD)31,34  have been reported but require independent confirmation. Finally, de novo variant (DNV) analysis of a PAH parent-child trio cohort (n = 124 trios) identified an important role of DNVs across all genes in pediatric-onset PAH,31  but larger cohorts are needed to confirm the role of individual genes (see below).

PH differs from adult-onset disease in several important aspects including sex bias, associated clinical features, etiology, and response to therapy. Data from the National Biological Sample and Data Repository for PAH (PAH Biobank)3, 31  indicate a markedly lower female sex bias among children with PAH (Table 2), suggesting less dependence on sex-specific factors. Children present with higher pulmonary artery pressure, decreased cardiac output, and higher pulmonary vascular resistance compared to adults (Table 2). Common comorbidities in pediatric PAH include CHD and developmental syndromes in contrast to the age-related cardiopulmonary and metabolic diseases commonly associated with adult-onset PAH. Data from the Pediatric PH Network Registry35  underscore the role of congenital and developmental diseases in pediatric PH, with >75% of Group 1 and Group 3 cases associated with CHD, bronchopulmonary dysplasia, congenital diaphragmatic hernia (CDH), or other rare developmental syndromes or anomalies (Table 3). Relative to adult-onset PH, pediatric PH has been vastly understudied, and little is known regarding the natural history, mechanisms of disease, and treatment of PH in children. The standard of care for pediatric PH patients is primarily based on extrapolations from adult data with only 1 pharmaceutical therapy approved by the Federal Drug Administration for use in children because of the lack of safety and efficacy data.

Table 2

Clinical Characteristics and Hemodynamic Parameters of Pediatric-Onset vs Adult-Onset PAH Cases at Diagnosis. Data From PAH Biobank (n = 2572 Cases). Pediatric-Onset, <18 Years of Age at Diagnosis. Mean ± SD

Clinical Characteristics and Hemodynamic Parameters of Pediatric-Onset vs Adult-Onset PAH Cases at Diagnosis. Data From PAH Biobank (n = 2572 Cases). Pediatric-Onset, <18 Years of Age at Diagnosis. Mean ± SD
Clinical Characteristics and Hemodynamic Parameters of Pediatric-Onset vs Adult-Onset PAH Cases at Diagnosis. Data From PAH Biobank (n = 2572 Cases). Pediatric-Onset, <18 Years of Age at Diagnosis. Mean ± SD
Table 3

Frequent Occurrence of Developmental Comorbidities in Pediatric PH. Data From the Pediatric Pulmonary Hypertension Network (n = 1475 Cases)36 

Frequent Occurrence of Developmental Comorbidities in Pediatric PH. Data From the Pediatric Pulmonary Hypertension Network (n = 1475 Cases)36
Frequent Occurrence of Developmental Comorbidities in Pediatric PH. Data From the Pediatric Pulmonary Hypertension Network (n = 1475 Cases)36

Emerging data from genetic studies of Group 1 PAH indicate that the genetic basis in children is different from that of adults.36  We recently combined data from our Columbia University Irving Medical Center PAH cohort16,32  and the PAH Biobank3,31  to compare the genetic contribution of inherited and DNVs in pediatric- vs adult-onset PAH, including PAH associated with other diseases. We identified a greater genetic burden of rare pathogenic/likely pathogenic variants among pediatric-onset PAH cases (~43%) compared to adult-onset cases (~13%) (Figure 1).37  DNVs are the most frequent genetic etiology of PAH in children, likely contributing to ~15% of all cases. While a few DNVs have been identified in known PAH risk genes – ACVRL1, BMPR2, TBX4 – the vast majority of the genes are novel candidate genes. Three of the genes are known CHD genes (NOTCH1, PTPN11, PSMD12), and we previously reported rare inherited variants in PAH associated with CHD cases for NOTCH1 (n = 5) and PTPN11 (n = 1). NOTCH1 is the most commonly associated gene for the congenital heart defect of tetralogy of Fallot,38  and the NOTCH1 DNV carrier had a diagnosis of PAH associated with CHD with tetralogy of Fallot. Rare variants in PTPN11 and RAF1 are causal for Noonan syndrome, which has a high frequency of congenital heart defects. The DNVs identified in both of these genes are known causal Noonan syndrome variants,39  and at least 3 cases of fatal pediatric PAH with Noonan syndrome have been previously reported.40,41  Of note, 37% of the candidate genes identified by DNV analysis are causal genes for rare developmental syndromes.42  Novel genes with plausible roles in lung/vascular development but not previously implicated in PH are listed in Table 4. Notably, variants in the novel genes have not been observed in adult-onset cases and likely are specific to pediatric PH.

Figure 1:

Relative contribution of de novo variants and 18 PAH risk genes in a cohort of 443 pediatric and 2628 adult PAH cases from Columbia University Irving Medical Center and the PAH Biobank. Risk genes included BMPR2, ABCC8, ACVRL1, ATP13A3, BMPR1A, BMPR1B, CAV1, EIF2AK4, ENG, GDF2, KCNA5, KCNK3, KDR, NOTCH1, SMAD1, SMAD4, and TBX4. PAH cases included IPAH, APAH, FPAH, and other rarer cases.

Figure 1:

Relative contribution of de novo variants and 18 PAH risk genes in a cohort of 443 pediatric and 2628 adult PAH cases from Columbia University Irving Medical Center and the PAH Biobank. Risk genes included BMPR2, ABCC8, ACVRL1, ATP13A3, BMPR1A, BMPR1B, CAV1, EIF2AK4, ENG, GDF2, KCNA5, KCNK3, KDR, NOTCH1, SMAD1, SMAD4, and TBX4. PAH cases included IPAH, APAH, FPAH, and other rarer cases.

Table 4

Novel Genes With de novo LGD or D-Mis Variants in Pediatric-Onset PAH (n = 124 trios)

Novel Genes With de novo LGD or D-Mis Variants in Pediatric-Onset PAH (n = 124 trios)
Novel Genes With de novo LGD or D-Mis Variants in Pediatric-Onset PAH (n = 124 trios)

The frequent presentation of pediatric PH with other congenital and early-onset comorbidities suggests that the causal genes in children have roles in cardiopulmonary development. Decreased lung vascular and alveolar growth predispose to vascular injury during susceptible periods of growth and adaptation. Histopathological studies have identified abnormal lung development and lung hypoplasia as common features of PAH, CHD, CDH, and Down syndrome43,44  Two established PAH genes, TBX4 and SOX17, are highly expressed in embryonic tissues and have roles in lung and vasculature development. Rare DNVs or heritable variants in these genes account for 5.6% (TBX4) and 4.3% (SOX17, usually associated with CHD) of pediatric PAH cases but less than 1% (TBX4) or rarely (SOX17) of adult-onset PAH. Although rare variants in SOX17 are an infrequent cause of PAH in adults, common variants in SOX17 contribute to adult PAH.45  Thus, different classes of variants in the same genes may contribute to and inform PAH across the lifespan.

While most PAH risk genes exhibit an autosomal dominant mode of inheritance in adult-onset PAH, there is increasing evidence of codominant inheritance in pediatric-onset PAH. For example, biallelic variants of ATP13A3, encoding an ATP-driven pump involved in polyamine homeostasis, were recently identified in 5 children from 3 families diagnosed under the age of 3 years with severe PAH largely refractory to treatment and associated with high mortality.46  These data suggest that ATP13A3 exhibits a dose-dependent effect in which 2 variant alleles cause severe, early-onset PAH. Together, the data from pediatric cohorts indicate that there is a greater genetic burden, differences in causal variant type and class, and increased occurrence of biallelic inheritance compared with adult-onset disease. Thus, studies of children will likely identify a greater number and broader spectrum of PH risk genes, and may also lead to insights in adult PH.

DNVs have emerged as an important class of genetic factors underlying early-onset, rare, and lethal developmental disorders47,48  because of strong negative selection decreasing reproductive fitness.49  These genes tend to be constrained genes that are intolerant to loss of function alleles,50,51  involved in coordinated organogenesis, and include transcription factors, RNA-binding proteins, protein kinases, and chromatin modification. While we have demonstrated a significant contribution of DNVs in pediatric PAH,16,31  our studies have been underpowered to definitively implicate which of the large numbers of genes identified are truly associated with PH. We recently identified LONP1 as a CDH causal gene in the DHREAMS pediatric CDH cohort.52  Using 827 child-parent trios, we identified CDH cases with rare deleterious de novo missense variants implicating LONP1 at a false discovery rate <0.05. Nearly 3% of the CDH cases had likely gene-disrupting or deleterious missense variants. We further demonstrated that heterozygous individuals with rare variants in LONP1 had PH with higher mortality and greater need for extracorporeal membrane oxygenation compared to noncarriers. LONP1 is a nuclear-encoded mitochondrial protease. Using a novel conditional knockout mouse model, we showed that inactivation of LONP1 in embryonic lung epithelium only with an intact diaphragm leads to disrupted lung development and 100% neonatal lethality (Figure 2). These data implicate a primary developmental lung defect independent of the CDH. The potential role of LONP1 in PH in general is unknown and will be part of future studies. Studies of CDH and CHD can complement and inform studies of pediatric PH, but independent PH cohorts are necessary for identifying PH risk genes because PH is not always associated with CDH/CHD and such cases may be harder to treat.

Figure 2:

Embryonic epithelial-specific inactivation of LONP1 causes immature, fluid-filled lungs in mice and neonatal lethality with intact diaphragm.

Figure 2:

Embryonic epithelial-specific inactivation of LONP1 causes immature, fluid-filled lungs in mice and neonatal lethality with intact diaphragm.

Genetic linkage and candidate gene studies indicate an autosomal dominant mode of inheritance for PAH risk, and most causal genetic factors for PAH are typically autosomal dominantly inherited, such as BMPR2.53,54  However, many individuals who carry monogenic risk variants in BMPR2 and other causal genes never develop PAH. This issue of incomplete penetrance suggests that additional genetic, epigenetic, environmental factors, and gene x environment interactions contribute to risk for PAH. Exome and genome sequencing studies have identified a subset of PAH cases with deleterious variants in more than one risk gene3,4,31  but the relative contribution of each risk allele to the development of PAH is unknown, including the potential for gene-gene interactions. Tests of oligogene or multiple-gene models will require hundreds of thousands of cases, clearly much greater than the number of cases in current cohorts. Similarly, identification of modifier genes affecting PAH penetrance is an area of great interest but will require larger cohorts.

Most of the large genetic studies conducted to date have used cohorts of predominantly European ancestry. However, the role of specific genes in PAH may be heterogeneous across genetic ancestries, and the results of these studies may not be generalizable to all other populations. For example, the frequency of ACVRL1 and ENG variants combined is ~1% among pediatric IPAH cases of European ancestry3,16  but the frequency of ACVRL1 variants alone may be closer to 13% among Asian children.55  As mentioned, GDF2 variants might be a more frequent cause of PAH among Asians compared to Europeans.3,4,11  Data from the PAH Biobank indicate that GDF2 variants may contribute more frequently to PAH cases of Asian (3/98 cases, 3.1%), Hispanic (8/309, 2.6%), and African (4/283, 1.4%) ancestries compared to Europeans (13/1852, 0.7%).3  Further study is required to determine whether these differences are true genetic ancestry effects or random differences due to relatively small sample size. A PAH case study of a 5-year-old boy of Hispanic ancestry identified a homozygous GDF2 likely gene-disrupting variant, and the unaffected parents were heterozygous for the variant.56  Interestingly, the gnomAD population database (gnomADv2.1.1, n = 141 456 samples)51  contains only 2 heterozygous counts of this allele, both of Latino ancestry, suggesting that this might be an ancestry-specific allele. Clearly, larger studies of PH with greater diversity are needed to define population-specific risk gene allele frequencies as well as ancestral-specific genetic factors.

In addition to DNA sequencing to identify genetic etiologies of PAH, other “omics” including RNA sequencing, metabolomics, and proteomics can provide valuable predictions of who is at risk for disease, define endophenotypes, and guide effective therapies.57,58  For example, West and colleagues performed RNA sequencing of blood lymphocytes derived from BMPR2 variant carriers with and without PAH to identify transcriptional patterns relevant to disease penetrance.59  More recently, FHIT was identified as a potentially clinically relevant BMPR2 modifier gene through an siRNA screen of BMPR2 signaling regulatory genes combined with publicly-available PAH RNA expression data. Subsequently, the authors showed that pharmaceutical upregulation of FHIT prevented and reversed experimental PH in a rat model.60  Stearman et al combined gene expression data with pathway analyses to identify a transcriptional framework for PAH-affected lungs.61  Similarly, Hemnes and colleagues used transcriptomics to identify RNA expression patterns predictive of vasodilator responsiveness among PAH patients.62  Rhodes and colleagues used metabolomics to identify circulating metabolites that distinguish PAH cases from healthy controls, predict outcomes among PAH cases, and to monitor metabolite levels over time to determine whether correction could affect outcomes.63  Notably, increased levels of polyamine metabolites were among the prognostic metabolites identified, and PAH causal gene, ATP13A3, encodes a key regulator of polyamine metabolism. These studies highlight the promise of other omics in predictions of PAH risk, diagnosis, classification, drug responsiveness, and prognosis.

Our data indicate that the diagnostic yield of genetic testing is especially high for pediatric PAH, approaching 50%, and education about the option for genetic testing is strongly recommended for all pediatric PAH and for adult patients with heritable PAH and IPAH. For children, analysis of child-parent trios can increase the diagnostic yield of exome sequencing up to 15% based on analysis of DNVs. Knowledge of genetic diagnoses can immediately impact clinical management of PH, including multimodal medical treatment, surgical intervention, transplantation decisions, and screening for associated conditions. A genetic diagnosis can lead to early treatment of associated medical conditions, cascade genetic testing of family members to identify those at risk for developing PAH, and can clarify reproductive risks to inform family planning decisions. Biallelic mutations in EIF2AK4 are diagnostic for pulmonary veno-occlusive disease/pulmonary capillary hemangiomatosis,64  which can be difficult to diagnose clinically without a lung biopsy, and patients can be listed for transplant earlier in the course of disease, which may improve outcomes. ACVRL1/ENG variant carriers with PAH associated with hereditary hemorrhagic telangiectasia are prone to arteriovenous malformations in brain, intestine, liver, and lung;65  these patients require periodic MRI surveillance. TBX4 variant carriers, especially children, are prone to other lung, cardiac, or skeletal defects19  and should be assessed by imaging studies and physical exam of the hands, hips, knees, and feet. In addition, a diagnosis of TBX4 variants in newborns with persistent PH indicates increased risk for developing PAH later in childhood,19  and these patients should be screened annually by echocardiography. Rare biallelic forms of very-early-onset severe PAH have recently been identified for ATP13A3,46 GDF2,56  and KCNK3.24  Such cases may be largely refractory to treatment and with high mortality, requiring early referral for surgery for a Potts shunt or lung transplantation.

While panel testing is often used for clinical diagnostic testing, the gene-sets included in panels are highly variable and can be limited in scope, so the gene list should be carefully reviewed. Decreasing cost and increasing availability of clinical exome and genome sequencing services66  will soon allow genomic sequencing tests to become the gold standard for genetic testing, either for adult patients with familial disease and without identified mutations from gene panels and in children regardless of family history. Exome/genome sequencing data provides a permanent dataset that can be reassessed over time as new risk genes are identified. Periodic reanalysis is highly recommended for cases without a diagnosis.

To support families with genetic diagnoses, gene-specific family support groups and virtual or in-person family meetings can be organized to update families on new findings related to their conditions and build communities for each of the rare subtypes. For example, TBX4Life is a recently organized and active family-based effort to raise awareness, educate families, and identify additional TBX4 variant carriers to enhance further research.

The genetic landscape of PH continues to emerge, primarily through genetic studies of PAH. Currently, the diagnostic yield for PAH is ~13% for adults and 43% for children. DNVs account for ~15% of pediatric-onset cases, but larger pediatric cohorts are needed to confirm the role of individual genes and identify new genes. LONP1 is a new CDH causal gene associated with PH, but the role of LONP1 in PH, in general, will require assessment in PH cohorts. Genetic sequencing tests are recommended for clinical diagnoses, are readily available, and are usually covered by insurance in the United States. Exome or genome sequencing allows for periodic reanalysis of cases with no initial genetic diagnosis. Clearly, there is a need for large, diverse, international consortia with ever-improving analytical pipelines to confirm known candidate genes, identify additional genes and variants, assess penetrance, the role of genetic ancestry, and characterize each genetic subtype including natural history, prognosis, and response to therapies to inform more precise clinical management.

1.
Wijeratne
DT,
Lajkosz
K,
Brogly
SB,
et al.
Increasing incidence and prevalence of World Health Organization Groups 1 to 4 Pulmonary Hypertension: a population-based cohort study in Ontario, Canada
.
Circ Cardiovasc Qual Outcomes
.
2018
;
11
(
2
):
e003973
.
2.
Simonneau
G,
Montani
D,
Celermajer
DS,
et al.
Haemodynamic definitions and updated clinical classification of pulmonary hypertension
.
Eur Respir J
.
2019
;
53
(
1
):
1801913
.
3.
Zhu
N,
Pauciulo
MW,
Welch
CL,
et al.
Novel risk genes and mechanisms implicated by exome sequencing of 2572 individuals with pulmonary arterial hypertension
.
Genome Med
.
2019
;
11
(
1
):
69
.
4.
Graf
S,
Haimel
M,
Bleda
M,
et al.
Identification of rare sequence variation underlying heritable pulmonary arterial hypertension
.
Nat Commun
.
2018
;
9
(
1
):
1416
.
5.
Kabata
H,
Satoh
T,
Kataoka
M,
et al.
Bone morphogenetic protein receptor type 2 mutations, clinical phenotypes and outcomes of Japanese patients with sporadic or familial pulmonary hypertension
.
Respirology
.
2013
;
18
(
7
):
1076
1082
.
6.
Navas
P,
Tenorio
J,
Quezada
CA,
et al.
Molecular analysis of BMPR2, TBX4, and KCNK3 and genotype-phenotype correlations in Spanish patients and families with idiopathic and hereditary pulmonary arterial hypertension
.
Rev Esp Cardiol (Engl Ed)
.
2016
;
69
(
11
):
1011
1019
.
7.
Abou Hassan
OK,
Haidar
W,
Nemer
G,
Skouri
H,
Haddad
F,
BouAkl
I.
Clinical and genetic characteristics of pulmonary arterial hypertension in Lebanon
.
BMC Med Genet
.
2018
;
19
(
1
):
89
.
8.
Evans
JD,
Girerd
B,
Montani
D,
et al.
BMPR2 mutations and survival in pulmonary arterial hypertension: an individual participant data meta-analysis
.
Lancet Respir Med
.
2016
;
4
(
2
):
129
137
.
9.
Yang
H,
Zeng
Q,
Ma
Y,
et al.
Genetic analyses in a cohort of 191 pulmonary arterial hypertension patients
.
Respir Res
.
2018
;
19
(
1
):
87
.
10.
Austin
ED,
Phillips
JA,
Cogan
JD,
et al.
Truncating and missense BMPR2 mutations differentially affect the severity of heritable pulmonary arterial hypertension
.
Respir Res
.
2009
;
10
(
1
):
87
.
11.
Wang
XJ,
Lian
TY,
Jiang
X,
et al.
Germline BMP9 mutation causes idiopathic pulmonary arterial hypertension
.
Eur Respir J
.
2019
;
53
(
3
):
1801609
.
12.
Bohnen
MS,
Ma
L,
Zhu
N,
et al.
Loss-of-function ABCC8 mutations in pulmonary arterial hypertension
.
Circ Genom Precis Med
.
2018
;
11
(
10
):
e002087
.
13.
Lago-Docampo
M,
Tenorio
J,
Hernandez-Gonzalez
I,
et al.
Characterization of rare ABCC8 variants identified in Spanish pulmonary arterial hypertension patients
.
Sci Rep
.
2020
;
10
(
1
):
15135
.
14.
Kerstjens-Frederikse
WS,
Bongers
EMHF,
Roofthooft
MTR,
et al.
TBX4 mutations (small patella syndrome) are associated with childhood-onset pulmonary arterial hypertension
.
J Med Genet
.
2013
;
50
(
8
):
500
506
.
15.
Nimmakayalu
M,
Major
H,
Sheffield
V,
et al.
Microdeletion of 17q22q23.2 encompassing TBX2 and TBX4 in a patient with congenital microcephaly, thyroid duct cyst, sensorineural hearing loss, and pulmonary hypertension
.
Am J Med Genet A
.
2011
;
155A
(
2
):
418
423
.
16.
Zhu
N,
Gonzaga-Jauregui
C,
Welch
CL,
et al.
Exome sequencing in children with pulmonary arterial hypertension demonstrates differences compared with adults
.
Circ Genom Precis Med
.
2018
;
11
(
4
):
e001887
.
17.
Sheeba
CJ
Logan
MP.
The roles of T-box genes in vertebrate limb development
.
Curr Top Dev Biol
.
2017
;
122
:
355
381
.
18.
Krause
A,
Zacharias
W,
Camarata
T,
et al.
Tbx5 and Tbx4 transcription factors interact with a new chicken PDZ-LIM protein in limb and heart development
.
Dev Biol
.
2004
;
273
(
1
):
106
120
.
19.
Galambos
C,
Mullen
MP,
Shieh
JT,
et al.
Phenotype characterisation of TBX4 mutation and deletion carriers with neonatal and pediatric pulmonary hypertension
.
Eur Respir J
.
2019
;
54
(
2
):
1801965
.
20.
Karolak
JA,
Vincent
M,
Deutsch
G,
et al.
Complex compound inheritance of lethal lung developmental disorders due to disruption of the TBX-FGF pathway
.
Am J Hum Genet
.
2019
;
104
(
2
):
213
228
.
21.
Best
DH,
Sumner
KL,
Austin
ED,
et al.
EIF2AK4 mutations in pulmonary capillary hemangiomatosis
.
Chest
.
2014
;
145
(
2
):
231
236
.
22.
Eyries
M,
Montani
D,
Girerd
B,
et al.
EIF2AK4 mutations cause pulmonary veno-occlusive disease, a recessive form of pulmonary hypertension
.
Nat Genet
.
2014
;
46
(
1
):
65
69
.
23.
Ma
L,
Roman-Campos
D,
Austin
ED,
et al.
A novel channelopathy in pulmonary arterial hypertension
.
N Engl J Med
.
2013
;
369
(
4
):
351
361
.
24.
Navas Tejedor
P,
Tenorio Castano
J,
Palomino Doza
J,
et al.
An homozygous mutation in KCNK3 is associated with an aggressive form of hereditary pulmonary arterial hypertension
.
Clin Genet
.
2017
;
91
(
3
):
453
457
.
25.
Cunningham
KP,
Holden
RG,
Escribano-Subias
PM,
Cogolludo
A,
Veale
EL,
Mathie
A.
Characterization and regulation of wild-type and mutant TASK-1 two pore domain potassium channels indicated in pulmonary arterial hypertension
.
J Physiol
.
2019
;
597
(
4
):
1087
1101
.
26.
Higasa
K,
Ogawa
A,
Terao
C,
et al.
A burden of rare variants in BMPR2 and KCNK3 contributes to a risk of familial pulmonary arterial hypertension
.
BMC Pulm Med
.
2017
;
17
(
1
):
57
.
27.
Austin
ED,
Ma
L,
LeDuc
C,
et al.
Whole exome sequencing to identify a novel gene (caveolin-1) associated with human pulmonary arterial hypertension
.
Circ Cardiovasc Genet
.
2012
;
5
(
3
):
336
343
.
28.
Han
B,
Copeland
CA,
Kawano
Y,
et al.
Characterization of a caveolin-1 mutation associated with both pulmonary arterial hypertension and congenital generalized lipodystrophy
.
Traffic
.
2016
;
17
(
12
):
1297
1312
.
29.
Copeland
CA,
Han
B,
Tiwari
A,
et al.
A disease-associated frameshift mutation in caveolin-1 disrupts caveolae formation and function through introduction of a de novo ER retention signal
.
Mol Biol Cell
.
2017
;
28
(
22
):
3095
3111
.
30.
Swietlik
EM,
Greene
D,
Zhu
N,
et al.
Bayesian inference associates rare KDR variants with specific phenotypes in pulmonary arterial hypertension
.
Circ Genom Precis Med
.
2020
;
14
(
1
):
e003155
.
31.
Zhu
N,
Swietlik
EM,
Welch
CL,
et al.
Rare variant analysis of 4241 pulmonary arterial hypertension cases from an international consortium implicates FBLN2, PDGFD, and rare de novo variants in PAH
.
Genome Med
.
2021
;
13
(
1
):
80
.
32.
Zhu
N,
Welch
CL,
Wang
J,
et al.
Rare variants in SOX17 are associated with pulmonary arterial hypertension with congenital heart disease
.
Genome Med
.
2018
;
10
(
1
):
56
.
33.
Voelkel
NF,
Vandivier
RW,
Tuder
RM.
Vascular endothelial growth factor in the lung
.
Am J Physiol Lung Cell Mol Physiol
.
2006
;
290
(
2
):
L209
L221
.
34.
Gelinas
SM,
Benson
CE,
Khan
MA,
et al.
Whole exome sequence analysis provides novel insights into the genetic framework of childhood-onset pulmonary arterial hypertension
.
Genes (Basel)
.
2020
;
11
(
11
):
1328
.
35.
Abman
SH,
Mullen
MP,
Sleeper
LA,
et al.
Characterisation of pediatric pulmonary hypertensive vascular disease from the PPHNet Registry [published online ahead of print June 17, 2021]
.
Eur Respir J
.
doi:
.
36.
Welch
CL
Chung
WK.
Genetics and other omics in pediatric pulmonary arterial hypertension
.
Chest
.
2020
;
157
(
5
):
1287
1295
.
37.
Welch
CL
Chung
WK.
Genetics and genomics of pediatric pulmonary arterial hypertension
.
Genes (Basel)
.
2020
;
11
(
10
):
1213
.
38.
Page
DJ,
Miossec
MJ,
Williams
SG,
et al.
Whole exome sequencing reveals the major genetic contributors to nonsyndromic tetralogy of fallot
.
Circ Res
.
2019
;
124
(
4
):
553
563
.
39.
Tartaglia
M,
Martinelli
S,
Stella
L,
et al.
Diversity and functional consequences of germline and somatic PTPN11 mutations in human disease
.
Am J Hum Genet
.
2006
;
78
(
2
):
279
290
.
40.
Hopper
RK,
Feinstein
JA,
Manning
MA,
Benitz
W,
Hudgins
L.
Neonatal pulmonary arterial hypertension and Noonan syndrome: two fatal cases with a specific RAF1 mutation
.
Am J Med Genet A
.
2015
;
167A
(
4
):
882
885
.
41.
Tinker
A,
Uren
N,
Schofield
J.
Severe pulmonary hypertension in Ullrich-Noonan syndrome
.
Br Heart J
.
1989
;
62
(
1
):
74
77
.
42.
Zhu
N,
Swietlik
EM,
Welch
CL,
et al.
Rare variant analysis of 4241 pulmonary arterial hypertension cases from an international consortium implicate FBLN2, PDGFD and rare de novo variants in PAH
.
Genome Med
.
2021
;
13
(
1
):
80
.
43.
Abman
SH,
Baker
C,
Gien
J,
Mourani
P,
Galambos
C.
The Robyn Barst Memorial Lecture: differences between the fetal, newborn, and adult pulmonary circulations: relevance for age-specific therapies (2013 Grover Conference series)
.
Pulm Circ
.
2014
;
4
(
3
):
424
440
.
44.
Bush
D,
Abman
SH,
Galambos
C.
Prominent intrapulmonary bronchopulmonary anastomoses and abnormal lung development in infants and children with down syndrome
.
J Pediatr
.
2017
;
180
:
156
162.e1
.
45.
Rhodes
CJ,
Batai
K,
Bleda
M,
et al.
Genetic determinants of risk in pulmonary arterial hypertension: international genome-wide association studies and meta-analysis
.
Lancet Respir Med
.
2019
;
7
(
3
):
227
238
.
46.
Machado
R,
Welch
CL,
Haimel
M,
et al.
Biallelic variants of ATP13A3 cause dose-dependent childhood-onset pulmonary arterial hypertension characterised by extreme morbidity and mortality[published online ahead of print September 7, 2021]
.
J Med Genet
.
doi:
.
47.
Homsy
J,
Zaidi
S,
Shen
Y,
Ware
JS,
Samocha
KE,
Karczewski
KJ,
et al.
De novo mutations in congenital heart disease with neurodevelopmental and other congenital anomalies
.
Science
.
2015
;
350
(
6265
):
1262
6
.
48.
Qi
H,
Yu
L,
Zhou
X,
et al.
De novo variants in congenital diaphragmatic hernia identify MYRF as a new syndrome and reveal genetic overlaps with other developmental disorders
.
PLoS Genet
.
2018
;
14
(
12
):
e1007822
.
49.
Veltman
JA
Brunner
HG.
De novo mutations in human genetic disease
.
Nat Rev Genet
.
2012
;
13
(
8
):
565
575
.
50.
Lek
M,
Karczewski
KJ,
Minikel
EV,
et al.
Analysis of protein-coding genetic variation in 60,706 humans
.
Nature
.
2016
;
536
(
7616
):
285
291
.
51.
Karczewski
KJ,
Francioli
LC,
Tiao
G,
et al.
The mutational constraint spectrum quantified from variation in 141,456 humans
.
Nature
.
2020
;
581
(
7809
):
434
443
.
52.
Qiao
L,
Xu
L,
Yu
L,
et al.
Rare and de novo variants in 827 congenital diaphragmatic hernia probands implicate LONP1 as candidate risk gene
.
Am J Hum Genet
.
2021
;
108
(
10
)
1964
1980
.
53.
Morrell
NW,
Aldred
MA,
Chung
WK,
et al.
Genetics and genomics of pulmonary arterial hypertension
.
Eur Respir J
.
2019
;
53
(
1
):
1801899
.
54.
Southgate
L,
Machado
RD,
Graf
S,
Morrell
NW.
Molecular genetic framework underlying pulmonary arterial hypertension
.
Nat Rev Cardiol
.
2020
;
17
(
2
):
85
95
.
55.
Chida
A,
Shintani
M,
Yagi
H,
et al.
Outcomes of childhood pulmonary arterial hypertension in BMPR2 and ALK1 mutation carriers
.
Am J Cardiol
.
2012
;
110
(
4
):
586
593
.
56.
Wang
G,
Fan
R,
Ji
R,
et al.
Novel homozygous BMP9 nonsense mutation causes pulmonary arterial hypertension: a case report
.
BMC Pulm Med
.
2016
;
16
:
17
.
57.
Hemnes
AR.
Using omics to understand and treat pulmonary vascular disease
.
Front Med (Lausanne)
.
2018
;
5
:
157
.
58.
Harbaum
L,
Rhodes
CJ,
Otero-Nunez
P,
Wharton
J,
Wilkins
MR.
The application of ‘omics’ to pulmonary arterial hypertension
.
Br J Pharmacol
.
2021
;
178
(
1
):
108
120
.
59.
West
J,
Cogan
J,
Geraci
M,
et al.
Gene expression in BMPR2 mutation carriers with and without evidence of pulmonary arterial hypertension suggests pathways relevant to disease penetrance
.
BMC Med Genomics
.
2008
;
1
:
45
.
60.
Dannewitz Prosseda
S,
Tian
X,
Kuramoto
K,
et al.
FHIT, a novel modifier gene in pulmonary arterial hypertension
.
Am J Respir Crit Care Med
.
2019
;
199
(
1
):
83
98
.
61.
Stearman
RS,
Bui
QM,
Speyer
G,
et al.
Systems analysis of the human pulmonary arterial hypertension lung transcriptome
.
Am J Respir Cell Mol Biol
.
2019
;
60
(
6
):
637
649
.
62.
Hemnes
AR,
Trammell
AW,
Archer
SL,
et al.
Peripheral blood signature of vasodilator-responsive pulmonary arterial hypertension
.
Circulation
.
2015
;
131
(
4
):
401
409
;
discussion 9.
63.
Rhodes
CJ,
Ghataorhe
P,
Wharton
J,
et al.
Plasma metabolomics implicates modified transfer RNAs and altered bioenergetics in the outcomes of pulmonary arterial hypertension
.
Circulation
.
2017
;
135
(
5
):
460
475
.
64.
Chaisson
NF,
Dodson
MW,
Elliott
CG.
Pulmonary capillary hemangiomatosis and pulmonary veno-occlusive disease
.
Clin Chest Med
.
2016
;
37
(
3
):
523
534
.
65.
Plauchu
H,
de Chadarevian
JP,
Bideau
A,
Robert
JM.
Age-related clinical profile of hereditary hemorrhagic telangiectasia in an epidemiologically recruited population
.
Am J Med Genet
.
1989
;
32
(
3
):
291
297
.
66.
Phillips
KA,
Douglas
MP,
Wordsworth
S,
Buchanan
J,
Marshall
DA.
Availability and funding of clinical genomic sequencing globally
.
BMJ Glob Health
.
2021
;
6
(
2
):
e004415
.

Author notes

Disclosure: The authors have no relevant personal financial relationships to disclose.