Gross BMPR2 gene rearrangements constitute a new cause for primary pulmonary hypertension.

Approximately 50% of patients with familial primary pulmonary hypertension (FPPH) have been reported to have mutations within the bone morphogenic protein receptor type 2 (BMPR2) gene. The vast majority of these mutations were identified by PCR amplification and sequencing of individual exons. The aim of our study was to determine if additional BMPR2 mutations not found by exon sequencing alone could account for a significant portion of these negative cases. We examined DNA samples from 12 families, previously found to be negative for BMPR2 mutations, to identify any large BMPR2 gene rearrangements. Southern blot analysis found large gene rearrangements in four (33%) unrelated kindreds. Further analysis by reverse transcriptase PCR (RT-PCR) of BMPR2 transcripts from two of these kindreds found one to be heterozygous for a exon 10 duplication and the second to be heterozygous for a deletion of exons 4 to 5. Nonhomologous recombination is believed to be the cause of these large insertions/deletions. Our results demonstrate the inherent problems associated with exon-by-exon sequencing and the importance of other screening methods such as Southern blot and RT-PCR in the identification of BMPR2 mutations.