Total submissions: 3
| Submitter | RCV | SCV | Clinical significance | Condition | Last evaluated | Review status | Method | Comment |
|---|---|---|---|---|---|---|---|---|
| Labcorp Genetics |
RCV001983418 | SCV002267985 | likely pathogenic | Dilated cardiomyopathy 1G; Autosomal recessive limb-girdle muscular dystrophy type 2J | 2022-01-21 | criteria provided, single submitter | clinical testing | This variant is located in the A band of TTN (PMID: 25589632). Truncating variants in this region are significantly overrepresented in patients affected with dilated cardiomyopathy (PMID: 25589632). Truncating variants in this region have also been reported in individuals affected with autosomal recessive centronuclear myopathy (PMID: 23975875). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site. This variant has not been reported in the literature in individuals affected with TTN-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change creates a premature translational stop signal (p.Thr32555Lysfs*6) in the TTN gene. While this is not anticipated to result in nonsense mediated decay, it is expected to create a truncated TTN protein. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. |
| Ambry Genetics | RCV002361359 | SCV002662092 | likely pathogenic | Cardiovascular phenotype | 2023-03-09 | criteria provided, single submitter | clinical testing | The c.70452_70468dup17 variant, located in coding exon 177 of the TTN gene, results from a duplication of AAATAAAGTACCTGTGA at nucleotide position 70452, causing a translational frameshift with a predicted alternate stop codon (p.T23490Kfs*6). This exon is located in the A-band region of the N2-B isoform of the titin protein and is constitutively expressed in TTN transcripts (percent spliced in or PSI 100%). This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). This alteration is expected to result in loss of function by premature protein truncation or nonsense-mediated mRNA decay. While truncating variants in TTN are present in 1-3% of the general population, truncating variants in the A-band are the most common cause of dilated cardiomyopathy (DCM) (Herman DS et al. N. Engl. J. Med., 2012 Feb;366:619-28; Roberts AM et al. Sci Transl Med, 2015 Jan;7:270ra6). TTN truncating variants encoded in constitutive exons (PSI >90%) have been found to be significantly associated with DCM regardless of their position in titin (Schafer S et al. Nat. Genet., 2017 01;49:46-53). As such, this alteration is classified as likely pathogenic. |
| Molecular Genetics, |
RCV003994373 | SCV004812533 | likely pathogenic | Primary dilated cardiomyopathy | 2024-02-05 | criteria provided, single submitter | clinical testing | This sequence change in TTN is a frameshift variant predicted to cause a premature stop codon, p.(Thr32555Lysfs*6), in constitutively expressed exon 350 (percentage splice in, PSI, 100%) in the A-band. High PSI truncating variants in TTN have a significant association with dilated cardiomyopathy (PMID: 31216868). The highest population minor allele frequency in the population database gnomAD v4.0 is 0.0002% (2/1,111,496 alleles) in the European (non-Finnish) population, which is consistent with dilated cardiomyopathy. The variant has been reported in a study of cardiomyopathy and atrial fibrillation prevalence using the UK biobank but the affected status of the carrier is not stated (PMID: 36637017). Based on the classification scheme RMH Modified ACMG/AMP Guidelines v1.6.1, this variant is classified as LIKELY PATHOGENIC. Following criteria are met: PVS1, PM2_Supporting. |