letter nature genetics • volume 30 • february 2002 201 M utations of TTN, encoding the giant muscle filament titin, cause familial dilated cardiomyopathy Brenda Gerull 1,2 *, Michael Gramlich 1 *, John Atherton 3 , Mark McNabb 4 , Karoly Trombitás 4 , Sabine Sasse- Klaassen 1 , J.G. Seidman 5 , Christine Seidman 6 , Henk Granzier 4 , Siegfried Labeit 7 , Michael Frenneaux 8 & Ludwig Thierfelder 1,2 *These authors contributed equally to this work. 1 Max-Delbrueck Center for Molecular Medicine, D-13092 Berlin-Buch, Germany. 2 HELIOS Kliniken GmbH, Franz-Volhard Klinik, Charité, Humboldt- University, Berlin, Germany. 3 Department of Cardiology, Royal Brisbane Hospital, Brisbane, Australia. 4 Department of Veterinary and Comparative Anatomy, Pharmacology and Physiology, Washington State University, Pullman, Washington 99164-6520, USA. 5 Department of Genetics and Howard Hughes Medical Institute, Harvard Medical School, Boston Massachusetts 02115, USA. 6 Cardiovascular Division and Howard Hughes Medical Institute, Brigham and Women´s Hospital, Boston, Massachusetts 02115, USA. 7 Anesthesiology and Intensive Operative Medicine, University Hospital Mannheim, D-68135 Mannheim, Germany. 8 Department of Cardiology, University of Wales College of Medicine, Cardiff, UK. Correspondence should be addressed to L.T. (e-mail: lthier@mdc-berlin.de). Congestive heart failure (CHF) can result from various disease states with inadequate cardiac output. CHF due to dilated cardiomyopathy (DCM) is a familial disease in 20–30% of cases and is associated with mutations in genes encoding cytoskeletal, contractile or inner–nuclear membrane proteins 1 . We show that mutations in the gene encoding giant-muscle filament titin (TTN) cause autosomal dominant DCM linked to chromosome 2q31 (CMD1G; MIM 604145). Titin molecules extend from sarcomeric Z-discs to M-lines, provide an extensible scaffold for the contractile machinery and are crucial for myofibrillar elasticity and integrity 2 . In a large DCM kindred, a segregating 2-bp insertion mutation in TTN exon 326 causes a frameshift, truncating A-band titin. The truncated protein of approximately 2 mD is expressed in skeletal muscle, but western blot studies with epitope-spe- cific anti-titin antibodies suggest that the mutant protein is truncated to a 1.14-mD subfragment by site-specific cleav- age. In another large family with DCM linked to CMD1G, a TTN missense mutation (Trp930Arg) is predicted to disrupt a highly conserved hydrophobic core sequence of an immunoglobulin fold located in the Z-disc–I-band transition zone. The identification of TTN mutations in individuals with CMD1G should provide further insights into the pathogene- sis of familial forms of CHF and myofibrillar titin turnover. Published online: 14 January 2002, DOI: 10.1038/ng815 4 3 5 1 2 3 5 15 16 17 18 13 14 11 8 7 6 9 2 1 10 12 4 + + + – 4 12 11 6 5 2 3 13 16 17 7 8 15 20 22 18 19 21 32 30 31 33 28 24 25 26 27 9 23 14 1 10 29 + + + + + + + + + – – – – – – – – – – – – – – – – – 10 9 1 3 7 8 2 4 5 6 + + + + + + + + – – 2 1 I II III IV V Fig. 1 TTN mutation in DCM kin- dred A1. a, Pedigree of kindred A1 with autosomal dominant DCM. Filled, open and shaded symbols denote clinically affected, unaffected and unde- termined disease status, respec- tively. Presence of the TTN truncation mutation is indicated by a ‘+’, absence by a ‘–’ in those individuals available for muta- tion analysis. b, Partial nucleotide sequences of cloned wildtype (WT) and mutated (M) exon 326 alleles. The 2-bp inser- tion (AT) is indicated by arrows. Four mutant amino-acid residues and a premature stop codon are shown in bold. c, Western blot of skeletal muscle biopsy specimen from an affected member of family A1. India-ink strip indi- cates bands normally seen in skeletal muscle samples 8 and an extra band only reacting with antibodies that bind N-termi- nally of I84–86. In the control lane, the first antibody is omit- ted. T1, undegraded titin; T2, degraded titin containing A- band segment; MYH, myosin heavy chain. India ink Z1Z2 /T12 I80–81 I84–86 I109–111 A168/169 /M7–9 control T1 T2 truncated titin nebulin titin MYH Ile Thr Gly Tyr Val Ile Ile Ser Leu Ala Met Stop WT M a b c © 2002 Nature Publishing Group http://genetics.nature.com