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

Area of Science:

• Genetics
• Cardiovascular Medicine
• Molecular Biology

Background:

• Familial primary pulmonary hypertension (FPPH) is often linked to mutations in the bone morphogenic protein receptor type 2 (BMPR2) gene.
• Current mutation detection primarily relies on PCR amplification and sequencing of individual exons.

Purpose of the Study:

• To investigate whether large BMPR2 gene rearrangements, missed by standard exon sequencing, contribute to FPPH in mutation-negative cases.
• To identify additional BMPR2 mutations in families with a negative genetic testing history.

Main Methods:

• Analysis of DNA samples from 12 FPPH families with previously negative BMPR2 mutation screening.
• Utilized Southern blot analysis to detect large gene rearrangements.
• Employed reverse transcriptase PCR (RT-PCR) to analyze BMPR2 transcripts for rearrangements.

Main Results:

• Southern blot identified large BMPR2 gene rearrangements in 4 out of 12 (33%) families.
• RT-PCR confirmed a heterozygous exon 10 duplication in one family and a deletion of exons 4-5 in another.
• Nonhomologous recombination is proposed as the mechanism for these large insertions/deletions.

Conclusions:

• Exon-by-exon sequencing alone is insufficient for comprehensive BMPR2 mutation screening in FPPH.
• Southern blot and RT-PCR are crucial complementary methods for detecting large BMPR2 gene rearrangements.
• Identifying these rearrangements improves diagnostic yield in FPPH.