title: 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.affiliation: Institute of Molecular and Cell Physiology, Hannover Medical School, Carl Neuberg Str. 1, 30625 Hannover, Germany.
authors.forename: Snigdha
authors.initials: S
authors.lastname: Tripathi
authors.forename: Imke
authors.initials: I
authors.lastname: Schultz
authors.forename: Edgar
authors.initials: E
authors.lastname: Becker
authors.forename: Judith
authors.initials: J
authors.lastname: Montag
authors.forename: Bianca
authors.initials: B
authors.lastname: Borchert
authors.forename: Antonio
authors.initials: A
authors.lastname: Francino
authors.forename: Francisco
authors.initials: F
authors.lastname: Navarro-Lopez
authors.forename: Andreas
authors.initials: A
authors.lastname: Perrot
authors.forename: Cemil
authors.initials: C
authors.lastname: Özcelik
authors.forename: Karl-Josef
authors.initials: KJ
authors.lastname: Osterziel
authors.forename: William J
authors.initials: WJ
authors.lastname: McKenna
authors.forename: Bernhard
authors.initials: B
authors.lastname: Brenner
authors.forename: Theresia
authors.initials: T
authors.lastname: Kraft
mesh_terms: D000328:Adult; D000483:Alleles; D022981:Allelic Imbalance; D024741:Cardiomyopathy, Hypertrophic, Familial / Q000235:genetics*; D004252:DNA Mutational Analysis; D005838:Genotype; D006801:Humans; D008875:Middle Aged; D020125:Mutation, Missense; D010375:Pedigree; D020871:RNA Stability; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D024723:Ventricular Myosins / Q000235:genetics*; D055815:Young Adult
chemical_list: D012333:RNA, Messenger; D024723:Ventricular Myosins