BACKGROUND Dilated cardiomyopathy and hypertrophic cardiomyopathy arise from mutations in many genes. TTN, the gene encoding the sarcomere protein titin, has been insufficiently analyzed for cardiomyopathy mutations because of its enormous size. METHODS We analyzed TTN in 312 subjects with dilated cardiomyopathy, 231 subjects with hyper-trophic cardiomyopathy, and 249 controls by using next-generation or dideoxy sequencing. We evaluated deleterious variants for cosegregation in families and assessed clinical characteristics. RESULTS We identified 72 unique mutations (25 nonsense, 23 frameshift, 23 splicing, and 1 large tandem insertion) that altered full-length titin. Among subjects studied by means of next-generation sequencing, the frequency of TTN mutations was significantly higher among subjects with dilated cardiomyopathy (54 of 203 [27%]) than among subjects with hypertrophic cardiomyopathy (3 of 231 [1%], P = 3×10−16) or controls (7 of 249 [3%], P = 9×10−14). TTN mutations cosegregated with dilated cardiomyopathy in families (combined lod score, 11.1) with high (>95%) observed penetrance after the age of 40 years. Mutations associated with dilated cardiomyopathy were overrepresented in the titin A-band but were absent from the Z-disk and M-band regions of titin (P≤0.01 for all comparisons). Overall, the rates of cardiac outcomes were similar in subjects with and those without TTN mutations, but adverse events occurred earlier in male mutation carriers than in female carriers (P = 4×10−5). CONCLUSIONS TTN truncating mutations are a common cause of dilated cardiomyopathy, occurring in approximately 25% of familial cases of idiopathic dilated cardiomyopathy and in 18% of sporadic cases. Incorporation of sequencing approaches that detect TTN truncations into genetic testing for dilated cardiomyopathy should substantially increase test sensitivity, thereby allowing earlier diagnosis and therapeutic intervention for many patients with dilated cardiomyopathy. Defining the functional effects of TTN truncating mutations should improve our understanding of the pathophysiology of dilated cardiomyopathy. (Funded by the Howard Hughes Medical Institute and others.)

Substantial progress has been made recently in understanding the genetic basis of cardiomyopathy. Cardiomyopathies with known genetic cause include hypertrophic (HCM), dilated (DCM), restrictive (RCM), arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) and left ventricular noncompaction (LVNC). HCM, DCM, and RCM have been recognized as distinct clinical entities for decades, whereas ARVD/C and LVNC are relative newcomers to the field. Hence the clinical and genetic knowledge for each cardiomyopathy varies, as do the recommendations and strength of evidence.

Background-We studied a large family affected by an autosomal dominant cardiac conduction disorder associated with sinus node dysfunction, arrhythmia, and right and occasionally left ventricular dilatation and dysfunction. Previous linkage analysis mapped the disease phenotype to a 30-cM region on chromosome 3p22-p25 (CMD1E). This region also contains a locus for right ventricular cardiomyopathy (ARVD5) and the cardiac sodium channel gene (SCN5A), mutations that cause isolated progressive cardiac conduction defect (Lenègre syndrome), long-QT syndrome (LQT3), and Brugada syndrome. Methods and Results-Family members were studied, and the positional candidate gene SCN5A was screened for mutations. We identified, by direct sequencing, a heterozygous G-to-A mutation at position 3823 that changed an aspartic acid to asparagine (D1275N) in a highly conserved residue of exon 21. This mutation was present in all affected family members, was absent in 300 control chromosomes, and predicted a change of charge within the S3 segment of domain III. Conclusions-Our findings expand the clinical spectrum of disorders of the cardiac sodium channel to include cardiac dilation and dysfunction and support the hypothesis that genes encoding ion channels can be implicated in dilated cardiomyopathies. Key Words: genetics Ⅲ cardiomyopathy Ⅲ conduction Ⅲ arrhythmia Ⅲ heart block I n 1986, Greenlee et al 1 reported a peculiar form of dilated cardiomyopathy (DCM) after studying a large pedigree of German and Swiss ancestry. The affected phenotype included sinus node dysfunction in adolescence, supraventricular tachyarrhythmia, and a progressive atrioventricular (AV) and intraventricular conduction delay that led to permanent pacing in most cases. The phenotype was also characterized by a progression toward atrial dilatation, frequently followed by right ventricular dilatation and, in some cases, left ventricular dilatation and dysfunction. 1 Subsequent linkage analysis mapped the disease locus to chromosome 3p22-p25 (CMD1E; OMIM %601154), which contains the voltagegated ␣-subunit of the cardiac sodium channel (SCN5A) gene. 2 SCN5A mutations have been associated with progressive cardiac conduction defect (Lenègre syndrome), isolated cardiac conduction disease, AV conduction block, sick sinus syndrome, sudden infant death syndrome, long-QT syndrome, and Brugada syndrome. [3][4][5][6][7][8][9] This chromosomal region also contains a locus for right ventricular cardiomyopathy (ARVD5). 10 We hypothesized that SCN5A mutations might be responsible for causing the conduction-related phenotype within this family (pedigree DN-ADFDC3; Figure 1A) and report the identification of an SCN5A mutation associated with the disease phenotype. Methods Clinical InvestigationInformed written consent was obtained from participants according to our protocol approved by the Colorado Multiple Institutional Review Board. The proband (IV-2 in Figure 1A) in the present study and his first-degree relatives (III-4, III-5, IV-1, and IV-4 in Figure 1A) were evaluated at t...

Background: Danon disease is a rare but serious cardiac and skeletal myopathy leading to substantial morbidity and early mortality due to arrhythmia and cardiomyopathy. The X-linked nature of inheritance accounts for reported differences in phenotypic severity between men and women. The rarity of Danon disease has limited understanding of the complete phenotype. Clinical estimates of ages of disease onset and survival based on gender have not been published. Methods and Results: We present data on 82 patients with Danon disease from 36 families, the largest series to date. Men were severely affected with cognitive disabilities (100%), hypertrophic cardiomyopathy (88%), and muscle weakness (80%). Men had a high morbidity and were unlikely to reach the age of 25 years without a cardiac transplantation. Women were less severely affected but reported higher than expected levels of cognitive (47%) and skeletal muscle complaints (50%) and manifesting an equal prevalence of dilated cardiomyopathy and hypertrophic cardiomyopathy. Combining our data with that of 63 other Danon disease case reports in the literature, the average ages of first symptom, cardiac transplantation, and death were 12.1, 17.9, and 19.0 years in men and 27.9, 33.7, and 34.6 years in women, respectively. Conclusion: These data more broadly illuminate the Danon disease phenotype and should prove useful to physicians working with and providing genetic counseling to families with Danon disease. Women with Danon disease present with clinical symptoms and events approximately 15 years after men and report a higher proportion of cognitive and skeletal muscle problems than previously recognized. Genet Med 2011:13(6):563-568.

Background Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited genetic myocardial disease characterized by fibrofatty replacement of the myocardium and a predisposition to cardiac arrhythmias and sudden death. We evaluated the cardiomyopathy gene titin (TTN) as a candidate ARVC gene because of its proximity to an ARVC locus at position 2q32 and the connection of the titin protein to the transitional junction at intercalated disks. Methods and Results All 312 titin exons known to be expressed in human cardiac titin and the complete 3’ untranslated region were sequenced in 38 ARVC families. Eight unique TTN variants were detected in 7 families including a prominent Thr2896Ile mutation that showed complete segregation with the ARVC phenotype in one large family. The Thr2896IIe mutation maps within a highly conserved immunoglobulin-like fold (Ig10 domain), located in titin’s spring region. Native gel electrophoresis, NMR, intrinsic fluorescence, and proteolysis assays of wildtype and mutant Ig10 domains revealed that the Thr2896IIe exchange reduces the structural stability and increases the propensity towards degradation of the Ig10 domain. The phenotype of TTN variant carriers was characterized by history of sudden death (5/7 families), progressive myocardial dysfunction causing death or heart transplant (8/14 cases), frequent conduction disease (11/14), and incomplete penetrance (86%). Conclusions Our data provide evidence that titin mutations can cause ARVC, a finding that further expands the origin of the disease beyond desmosomal proteins. Structural impairment of the titin spring is a likely cause of ARVC and constitutes a novel mechanism underlying myocardial remodeling and sudden cardiac death.

This guideline describes the approach and expertise needed for the genetic evaluation of cardiomyopathy. First published in 2009 by the Heart Failure Society of America (HFSA), the guideline has now been updated in collaboration with the American College of Medical Genetics and Genomics (ACMG). The writing group, composed of cardiologists and genetics professionals with expertise in adult and pediatric cardiomyopathy, reflects the emergence and increased clinical activity devoted to cardiovascular genetic medicine. The genetic evaluation of cardiomyopathy is a rapidly emerging key clinical priority, because high-throughput sequencing is now feasible for clinical testing and conventional interventions can improve survival, reduce morbidity, and enhance quality of life. Moreover, specific interventions may be guided by genetic analysis. A systematic approach is recommended: always a comprehensive family history; an expert phenotypic evaluation of the proband and at-risk family members to confirm a diagnosis and guide genetic test selection and interpretation; referral to expert centers as needed; genetic testing, with pre- and post-test genetic counseling; and specific guidance as indicated for drug and device therapies. The evaluation of infants and children demands special expertise. The approach to managing secondary and incidental sequence findings as recommended by the ACMG is provided.

In light of the limited efficacy of current treatments for cardiac regeneration, tissue engineering approaches have been explored for their potential to provide mechanical support to injured cardiac tissues, deliver cardio-protective molecules, and improve cell-based therapeutic techniques. Injectable hydrogels are a particularly appealing system as they hold promise as a minimally invasive therapeutic approach. Moreover, injectable acellular alginate-based hydrogels have been tested clinically in patients with myocardial infarction (MI) and show preservation of the left ventricular (LV) indices and left ventricular ejection fraction (LVEF). This review provides an overview of recent developments that have occurred in the design and engineering of various injectable hydrogel systems for cardiac tissue engineering efforts, including a comparison of natural versus synthetic systems with emphasis on the ideal characteristics for biomimetic cardiac materials.

Mutations in SCN5A were detected in 1.7% of DCM families. Two-thirds (6 of 9) of all reported DCM mutations in SCN5A localize to the highly conserved homologous S3 and S4 transmembrane segments, suggesting a shared mechanism of disruption of the voltage-sensing mechanism of this channel leading to DCM. Not surprisingly, SCN5A mutation carriers show a strong arrhythmic pattern that has clinical and diagnostic implications.