Florence Coulet

Pulmonary arterial hypertension (PAH) is clinically characterized by a sustained elevation in mean pulmonary artery pressure leading to significant morbidity and mortality. The disorder is typically sporadic, and in such cases the term idiopathic PAH (IPAH) is used. However, cases that occur within families (familial PAH (FPAH)) display similar clinical and histopathological features, suggesting a common etiology. Heterozygous mutations of a type II member of the TGF-beta cell signaling superfamily known as BMPR2 on chromosome 2q33 have been identified in many kindreds with FPAH, yet display both reduced penetrance and sex bias. This report presents the compilation of data for 144 distinct mutations that alter the coding sequence of the BMPR2 gene identified in 210 independent PAH subjects. This large data set characterizes the extent of sequence variation and reveals that the majority (71%) of mutations in FPAH and IPAH comprise nonsense, frameshift, and splice-site defects, and gene rearrangements. These predict premature termination of the transcript with likely loss through the process of nonsense-mediated decay (NMD). A total of 44 missense mutations were identified that substitute amino acid residues at highly conserved sites within recognized functional domains of the mature receptor. We assess this category of mutations in the context of their heterogeneous effects on cell signaling when assayed by in vitro cell-based systems. Disease-causing mutation hot-spots within BMPR2 are summarized. Taken together, these observations are likely to aid in the development of targeted mutation detection strategies relevant for patient management. Finally, we examine the age- and sex-dependent reduced penetrance of BMPR2 mutations by reviewing bmpr2 animal models and the requirement for additional genetic and/or environmental modifiers of disease. In conclusion, these data provide compelling genetic evidence that haploinsufficiency is the predominant molecular mechanism underlying disease predisposition, and support the concept of a critical threshold of signaling activity below which disease may be precipitated.

RATIONALE: Germline mutations in the gene encoding for bone morphogenetic protein receptor 2 (BMPR2) are a cause of pulmonary arterial hypertension (PAH). OBJECTIVES: We conducted a study to determine the influence, if any, of a BMPR2 mutation on clinical outcome. METHODS: The French Network of Pulmonary Hypertension obtained data for 223 consecutive patients displaying idiopathic or familial PAH in whom point mutation and large size rearrangements of BMPR2 were screened for. Clinical, functional, and hemodynamic characteristics, as well as outcomes, were compared in BMPR2 mutation carriers and noncarriers. MEASUREMENTS AND MAIN RESULTS: Sixty-eight BMPR2 mutation carriers (28 familial and 40 idiopathic PAH) were compared with 155 noncarriers (all displaying idiopathic PAH). As compared with noncarriers, BMPR2 mutation carriers were younger at diagnosis of PAH (36.5 +/- 14.5 vs. 46.0 +/- 16.1 yr, P < 0.0001), had higher mean pulmonary artery pressure (64 +/- 13 vs. 56 +/- 13 mm Hg, P < 0.0001), lower cardiac index (2.13 +/- 0.68 vs. 2.50 +/- 0.73 L/min/m(2), P = 0.0005), higher pulmonary vascular resistance (17.4 +/- 6.1 vs. 12.7 +/- 6.6 mm Hg/L/min/m(2), P < 0.0001), lower mixed venous oxygen saturation (59 +/- 9% vs. 63 +/- 9%, P = 0.02), shorter time to death or lung transplantation (P = 0.044), and younger age at death (P = 0.002), but similar overall survival (P = 0.51). CONCLUSIONS: BMPR2 mutation carriers with PAH present approximately 10 years earlier than noncarriers, with a more severe hemodynamic compromise at diagnosis.

Abstract Rationale Activin A receptor type II-like kinase-1 (ACVRL1, also known as ALK1) mutation is a cause of hereditary hemorrhagic telangiectasia (HHT) and/or heritable pulmonary arterial hypertension (PAH). Objectives To describe the characteristics of patients with PAH carrying an ACVRL1 mutation. Methods We reviewed clinical, functional, and hemodynamic characteristics of 32 patients with PAH carrying an ACVRL1 mutation, corresponding to 9 patients from the French PAH Network and 23 from literature analysis. These cases were compared with 370 patients from the French PAH Network (93 with a bone morphogenetic protein receptor type 2 [BMPR2] mutation and 277 considered as idiopathic cases without identified mutation). Distribution of mutations in the ACVRL1 gene in patients with PAH was compared with the HHT Mutation Database. Measurements and Main Results At diagnosis, ACVRL1 mutation carriers were significantly younger (21.8 ± 16.7 yr) than BMPR2 mutation carriers and noncarriers (35.7 ± 14.9 and 47.6 ± 16.3 yr, respectively; P &amp;lt; 0.0001). In seven of the nine patients from the French PAH Network, PAH diagnosis preceded manifestations of HHT. ACVRL1 mutation carriers had better hemodynamic status at diagnosis, but none responded to acute vasodilator challenge and they had shorter survival when compared with other patients with PAH despite similar use of specific therapies. ACVRL1 mutations in exon 10 were more frequently observed in patients with PAH, as compared with what was observed in the HHT Mutation Database (33.3 vs. 5%; P &amp;lt; 0.0001). Conclusions ACVRL1 mutation carriers were characterized by a younger age at PAH diagnosis. Despite less severe initial hemodynamics and similar management, these patients had worse prognosis compared with other patients with PAH, suggesting more rapid disease progression.