Unequal allelic expression of wild-type and mutated β-myosin in familial hypertrophic cardiomyopathy.

Abstract

Familial hypertrophic cardiomyopathy (FHC) is an autosomal dominant disease, which in about 30% of the patients is caused by missense mutations in one allele of the β-myosin heavy chain (β-MHC) gene (MYH7). To address potential molecular mechanisms underlying the family-specific prognosis, we determined the relative expression of mutant versus wild-type MYH7-mRNA. We found a hitherto unknown mutation-dependent unequal expression of mutant to wild-type MYH7-mRNA, which is paralleled by similar unequal expression of β-MHC at the protein level. Relative abundance of mutated versus wild-type MYH7-mRNA was determined by a specific restriction digest approach and by real-time PCR (RT-qPCR). Fourteen samples from M. soleus and myocardium of 12 genotyped and clinically well-characterized FHC patients were analyzed. The fraction of mutated MYH7-mRNA in five patients with mutation R723G averaged to 66 and 68% of total MYH7-mRNA in soleus and myocardium, respectively. For mutations I736T, R719W and V606M, fractions of mutated MYH7-mRNA in M. soleus were 39, 57 and 29%, respectively. For all mutations, unequal abundance was similar at the protein level. Importantly, fractions of mutated transcripts were comparable among siblings, in younger relatives and unrelated carriers of the same mutation. Hence, the extent of unequal expression of mutated versus wild-type transcript and protein is characteristic for each mutation, implying cis-acting regulatory mechanisms. Bioinformatics suggest mRNA stability or splicing effectors to be affected by certain mutations. Intriguingly, we observed a correlation between disease expression and fraction of mutated mRNA and protein. This strongly suggests that mutation-specific allelic imbalance represents a new pathogenic factor for FHC.

• Authors: Snigdha Tripathi, Imke Schultz, Edgar Becker, Judith Montag, Bianca Borchert, Antonio Francino, Francisco Navarro-Lopez, Andreas Perrot, Cemil Özcelik, Karl-Josef Osterziel, William J McKenna, Bernhard Brenner, Theresia Kraft
• Journal: Basic research in cardiology (Basic Res Cardiol) Vol. 106 Issue 6 Pg. 1041-55 (Nov 2011) ISSN: 1435-1803 [Electronic] Germany
• PMID: 21769673 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• RNA, Messenger
• Ventricular Myosins

Topics

• Adult
• Alleles
• Allelic Imbalance
• Cardiomyopathy, Hypertrophic, Familial (genetics)
• DNA Mutational Analysis
• Genotype
• Humans
• Middle Aged
• Mutation, Missense
• Pedigree
• RNA Stability
• RNA, Messenger (analysis, genetics)
• Real-Time Polymerase Chain Reaction
• Reverse Transcriptase Polymerase Chain Reaction
• Ventricular Myosins (genetics)
• Young Adult