Abstract

Background: Mutations have been identified in the bone morphogenetic protein receptor II (BMPR2) gene as the main cause for pulmonary arterial hypertension (PAH) in 85% hereditable PAH (HPAH) and 25% of idiopathic PAH cases. However, the penetrance of BMPR2 mutations is low indicating other modifiers such as promoter variants may contribute to disease manifestation.

Objectives: The aim of this study was to identify BMPR2 promoter mutations in HPAH and sporadic cases and to analyse their transcriptional effect on the BMPR2 gene expression.

Methods: BMPR2 promoter variants were screened by direct Sanger sequencing and next generation sequencing in IPAH/HPAH patients and their effect was investigated on BMPR2 promoter expression in in vitro. BMPR2 promoter regions containing identified variants were fused with a luciferase reporter gene. Recombinant plasmids were transfected into hPASMCs and transcriptional activity was assessed.

Results: Nine different BMPR2 promoter variants were identified in PAH families and IPAH patients. In the functional analysis, seven of the nine variants (c.-575A>T, c.-586dupT, c.-910C>T, c.-1141C>T, c.-930_-928dupGGC, c.-933_-928dupGGCGGC and c.-930_-928delGGC) led to a significantly decreased transcriptional activity in comparison to the wild-type.

Conclusion: This study identified new mutations in the BMPR2 promoter which could affect the BMPR2 gene expression. The mutations may act as a modifier at least in some families as they reduce the gene expression. Further studies are needed to investigate frequencies of BMPR2 promoter variants and their impact on penetrance and disease manifestation.