Abstract 16473: Cardiac Sodium Channel (scn5a) mRNA Splicing Abnormalities In Hypertrophic Cardiomyopathy
Background: Hypertrophic cardiomyopathy (HCM) leading to sustained ventricular tachyarrhythmias is the most common cause of sudden cardiac death (SCD) in young patients. Our previous studies showed that adult patients with heart failure (HF) at increased risk of SCD have increased abundance of alternatively spliced mRNA for the cardiac voltage-gated sodium channel (SCN5A) mRNA. These splice variants encode nonfunctional sodium channels that contribute to arrhythmic risk. In this project, we investigated the presence of splicing regulation of SCN5A in patients with HCM.
Methods: Human heart tissue was obtained from myectomy samples of HCM patients. Total RNA was extracted from the tissues from both HCM and normal controls for whole genome microarray analysis. The changes of relative abundances of SCN5A, its variants E28C, E28D, and the causative splicing factors RBM25, and Luc7A were confirmed by both real time RT-PCR and Western blot.
Results: The microarray data showed a significant decreased of SCN5A (P<0.01) and increased splicing factors such as Influenza virus NS1A binding protein, Peptidylprolyl isomerase G (cyclophilin G), Heterogeneous nuclear ribonucleoprotein A1, Cisplatin resistance-associated overexpressed protein (Luc7A) and RNA binding motif protein family members includes RBM25, RBM 39, RBM 33, RBM 20, RBM 42 in HCM patients. Real time RT-PCR revealed that HCM patients had a decreased SCN5A at 27.8% of control and an increased abundance of splice variant E28C and E28D (3.35 ± 0.29 and 2.75 ± 0.25-fold, respectively, P<0.05) compared to the hearts of normal controls. RBM25 and Luc7a increased 3.17 ± 0.47-fold (p<0.05) and 2.16 ± 0.39-fold (P<0.05) in patients with HCM, respectively. Western blot confirmed a significant increase of RBM25 of 1.6-fold (p<0.05).
Conclusion: Tissues from patients with HCM showed a decreased full length SCN5A transcript abundance, an increased abundance of abnormal SCN5A mRNA splice variants, and increased expression of splicing factors when compared to the hearts of normal controls. The results demonstrated that splicing regulation might play a key role in the pathogenesis of HCM patients. Because SCN5A variants can be measured in blood, changes mRNA might represent a marker of SCD in HCM.
- © 2012 by American Heart Association, Inc.