PTGIS is a Novel Susceptibility Gene for Pulmonary Arterial Hypertension

Background: Genetic variants such as inactivating mutation in the bone morphogenetic protein receptor 2 (BMPR2) gene account for approximately 15-20% of the etiology of idiopathic pulmonary arterial hypertension (IPAH). Increasing evidence indicates the existence of other IPAH susceptibility genes.   Methods: The whole-genome sequencing was performed in a discovery cohort including 42 IPAH patients who are lacking BMPR2 mutations. Putative IPAH genes were validated in an independent cohort that included 188 IPAH patients and 968 healthy controls. Functional assessments were conducted to analyze the effects of candidate genetic variants on transcript splicing, enzymatic activity and function.   Results: An enrichment of rare variants in the gene encoding prostacyclin synthase (PTGIS) was initially identified by the whole-genome sequencing. The association of PTGIS rare variants with IPAH was confirmed in the replication cohort. In total, fourteen patients (6.1%) were heterozygous for three PTGIS rare variants, including one splice-site variant (c.521 1G>A) and two missense variants (R252Q, A447T). These rare variants conferred a 7.8-fold greater risk of IPAH (95% confidence interval (CI), 3.2 to 18.8; P=5 x 10-6). Inhaled iloprost induced more significantly decrease of pulmonary vascular resistance (P=0.001) and increase of cardiac index (P A variant resulted in aberrant mRNA transcripts. The functional studies showed that the two missense variants caused a decrease in prostacyclin production and increased cell death in pulmonary microvascular endothelial cells.   Conclusions: We have identified three loss-of-function rare variants in the PTGIS gene from two independent IPAH cohorts. The genetic variants of PTGIS predispose pulmonary vascular responses to the iloprost stimulation and cause deleterious effects. These results provide a novel finding that PTGIS rare variants are involved in the pathogenesis of IPAH.    Funding: The work was supported by the following grants: the Beijing Natural Science Foundation (7181009, 7172180), the National Natural Science Foundation of China (81320108005), the National Science Fund for Distinguished Young Scholars (81425002), CAMS Innovation Fund for Medical Sciences (2016-I2M-1-002, 2016-I2M-4-003), the National Key Research and Development Program of China (2016YFC0901502), Sanming Project of Medicine in Shenzhen-Professor Zhi-Cheng Jing's Group for Precise Medicine Research in Thrombosis and Vascular Disease (SZSM201502001) , and the fund from State Key Laboratory of Cardiovascular Disease (2016-kf04, 2018ZR-02). Declaration of Interest: The authors declare no competing financial interests. Ethical Approval: The study protocol was approved by the ethics committees of Shanghai Pulmonary Hospital and FuWai Hospital. The participants, who were all of Chinese Han ancestry, provided written informed consent.