Description
Variant summary: TTN c.835C>T (p.Arg279Trp) results in a non-conservative amino acid change located in the Z-disk region of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 0.00019 in 282792 control chromosomes, predominantly at a frequency of 0.00036 within the Non-Finnish European subpopulation in the gnomAD database. This frequency is approximately equal to the estimated maximal expected allele frequency for a pathogenic variant in TTN causing Dilated Cardiomyopathy (0.00039), suggesting that the variant is a benign polymorphism found primarily in populations of Non-Finnish European origin. c.835C>T has been reported in the literature in multiple individuals affected with TTN-related conditions without strong evidence for causality (e.g., Lange_2005, Campuzan_2015, Sanchez_2016, van Spaendonck-Zwart_2014). At-least two co-occurrences with other pathogenic variant(s) have been reported in cis with this variant (TTN c.87491C>T, p.Pro29164Leu, Lange_2005; c.69086_69095del10, p.Arg23029ThrfsX9, van Spaendonck-Zwart_2014), providing supporting evidence for a benign role. Two publications report experimental evidence evaluating an impact on protein function, demonstrating reduced binding to nbd1 in mutant cells (Lange_2005, Chaveau_2014). However, neither study provides quantitative data indicating the strength of the effect. The following publications have been ascertained in the context of this evaluation (PMID: 26516846, 24105469, 24569025, 24578547, 27930701, 20708934, 24558114, 15802564, 24271327, 24231549). Eight submitters have cited clinical-significance assessments for this variant to ClinVar after 2014. Six submitters classified the variant as a variant of uncertain significance, and two classified it as likely benign. Based on the evidence outlined above, the variant was classified as likely benign.
# | Sample | Method | Observation |
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Origin | Affected | Number tested | Tissue | Purpose | Method | Individuals | Allele frequency | Families | Co-occurrences |
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1 | germline | unknown | not provided | not provided | not provided | | not provided | not provided | not provided | not provided |