Variant classified as Uncertain Significance - Favor Benign. The p.Arg12125Cys v ariant in TTN has not been previously reported in individuals with cardiomyopath y, but has been identified in 0.2% (20/9970) of African chromosomes by the Exome Aggregation Consortium (ExAC, http://exac.broadinstitute.org; dbSNP rs200445568 ). Computational prediction tools and conservation analysis suggest that this va riant may impact the protein, though this information is not predictive enough t o determine pathogenicity. In summary, while the clinical significance of the p. Arg12125Cys variant is uncertain, its frequency suggests that it is more likely to be benign.

This alteration is classified as likely benign based on a combination of the following: seen in unaffected individuals, population frequency, intact protein function, lack of segregation with disease, co-occurrence, RNA analysis, in silico models, amino acid conservation, lack of disease association in case-control studies, and/or the mechanism of disease or impacted region is inconsistent with a known cause of pathogenicity.

Variant summary: TTN c.36373C>T (p.Arg12125Cys) results in a non-conservative amino acid change in the encoded protein sequence. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change. The variant allele was found at a frequency of 0.00017 in 248510 control chromosomes, predominantly at a frequency of 0.0022 within the African or African-American subpopulation in the gnomAD database. The observed variant frequency within African or African-American control individuals in the gnomAD database is approximately 5.63 fold of the estimated maximal expected allele frequency for a pathogenic variant in TTN causing Dilated Cardiomyopathy phenotype (0.00039). c.36373C>T has been reported in the literature in one individual affected with sudden cardiac death (Campuzano_2018). These report(s) do not provide unequivocal conclusions about association of the variant with TTN-related conditions. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. The following publications have been ascertained in the context of this evaluation (PMID: 30086531, 34598035, 27302369, 27149842, 26771497). ClinVar contains an entry for this variant (Variation ID: 194910). Based on the evidence outlined above, the variant was classified as likely benign.

BS1;BP1

This variant is classified as likely benign based on ACMG/AMP sequence variant interpretation guidelines (Richards et al. 2015 PMID: 25741868, with internal and published modifications).