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CLINICAL RESEARCH: GENETICS/GENOMICS

Mutations in Ribonucleic Acid Binding Protein Gene Cause Familial Dilated Cardiomyopathy

Katharine M. Brauch, MS^_*, Margaret L. Karst, BA^_*, Kathleen J. Herron, BA^_*, Mariza de Andrade, PhD, Patricia A. Pellikka, MD, Richard J. Rodeheffer, MD, Virginia V. Michels, MD^|| and Timothy M. Olson, MD^_*,,,_*

^_* Cardiovascular Genetics Laboratory, College of Medicine, Mayo Clinic, Rochester, Minnesota
Division of Cardiovascular Diseases, Department of Internal Medicine, College of Medicine, Mayo Clinic, Rochester, Minnesota
Division of Pediatric Cardiology, Department of Pediatric and Adolescent Medicine, College of Medicine, Mayo Clinic, Rochester, Minnesota
Department of Health Sciences Research, College of Medicine, Mayo Clinic, Rochester, Minnesota
^|| Department of Medical Genetics, College of Medicine, Mayo Clinic, Rochester, Minnesota

Manuscript received February 18, 2009; revised manuscript received April 7, 2009, accepted May 10, 2009.

^_* Reprint requests and correspondence: Dr. Timothy M. Olson, Mayo Clinic, Stabile 5, 200 First Street Southwest, Rochester, Minnesota 55905 (Email: olson.timothy{at}mayo.edu).

Objectives: We sought to identify a novel gene for dilated cardiomyopathy (DCM).

Background: DCM is a heritable, genetically heterogeneous disorder that remains idiopathic in the majority of patients. Familial cases provide an opportunity to discover unsuspected molecular bases of DCM, enabling pre-clinical risk detection.

Methods: Two large families with autosomal-dominant DCM were studied. Genome-wide linkage analysis was used to identify a disease locus, followed by fine mapping and positional candidate gene sequencing. Mutation scanning was then performed in 278 unrelated subjects with idiopathic DCM, prospectively identified at the Mayo Clinic.

Results: Overlapping loci for DCM were independently mapped to chromosome 10q25-q26. Deoxyribonucleic acid sequencing of affected individuals in each family revealed distinct heterozygous missense mutations in exon 9 of RBM20, encoding ribonucleic acid (RNA) binding motif protein 20. Comprehensive coding sequence analyses identified missense mutations clustered within this same exon in 6 additional DCM families. Mutations segregated with DCM (peak composite logarithm of the odds score >11.49), were absent in 480 control samples, and altered residues within a highly conserved arginine/serine (RS)-rich region. Expression of RBM20 messenger RNA was confirmed in human heart tissue.

Conclusions: Our findings establish RBM20 as a DCM gene and reveal a mutation hotspot in the RS domain. RBM20 is preferentially expressed in the heart and encodes motifs prototypical of spliceosome proteins that regulate alternative pre-messenger RNA splicing, thus implicating a functionally distinct gene in human cardiomyopathy. RBM20 mutations are associated with young age at diagnosis, end-stage heart failure, and high mortality.

Key Words: dilated cardiomyopathy • genetics • linkage analysis • mutation • RBM20

Abbreviations and Acronyms   cDNA = complementary deoxyribonucleic acid   DCM = dilated cardiomyopathy   DHPLC = denaturing high-performance liquid chromatography   DNA = deoxyribonucleic acid   GEO = Gene Expression Omnibus   ICD = implantable cardioverter-defibrillator   LOD = logarithm of the odds   mRNA = messenger ribonucleic acid   NCBI = National Center for Biotechnology Information   PCR = polymerase chain reaction   RNA = ribonucleic acid   RS = arginine/serine

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