Affiliation:
1. From the Departments of Pediatrics (J.C., E.A., L.H., B.W., R.H.), Medicine (J.W., J.L.), and Cancer Biology (R.H.), Vanderbilt University Medical Center, Nashville, TN.
Abstract
Background—
Bone morphogenic protein receptor 2 (
BMPR2
) gene mutations are the most common cause of heritable pulmonary arterial hypertension. However, only 20% of mutation carriers get clinical disease. Here, we explored the hypothesis that this reduced penetrance is due in part to an alteration in
BMPR2
alternative splicing.
Methods and Results—
Our data showed that
BMPR2
has multiple alternative spliced variants. Two of these, isoform-A (full length) and isoform-B (missing exon 12), were expressed in all tissues analyzed. Analysis of cultured lymphocytes of 47
BMPR2
mutation–positive heritable pulmonary arterial hypertension patients and 35
BMPR2
mutation–positive unaffected carriers showed that patients had higher levels of isoform-B compared with isoform-A (B/A ratio) than carriers (
P
=0.002). Furthermore, compared with cells with a low B/A ratio, cells with a high B/A ratio had lower levels of unphosphorylated cofilin after BMP stimulation. Analysis of exon 12 sequences identified an exonic splice enhancer that binds serine arginine splicing factor 2 (
SRSF2
). Because
SRSF2
promotes exon inclusion, reduced
SRSF2
expression would mean that exon 12 would not be included in final
BMPR2
mRNA (thus promoting increased isoform-B formation). Western blot analysis showed that SRSF2 expression was lower in cells from patients compared with cells from carriers and that siRNA-mediated knockdown of
SRSF2
in pulmonary microvascular endothelial cells resulted in elevated levels of isoform-B compared with isoform-A, ie, an elevated B/A ratio.
Conclusions—
Alterations in
BMPR2
isoform ratios may provide an explanation of the reduced penetrance among
BMPR2
mutation carriers. This ratio is controlled by an exonic splice enhancer in exon 12 and its associated splicing factor, SRSF2.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Physiology (medical),Cardiology and Cardiovascular Medicine
Cited by
60 articles.
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