Our verdict is Likely benign. Variant got -1 ACMG points: 1P and 2B. PP2BP4_Moderate
The NM_001267550.2(TTN):āc.98866A>Gā(p.Met32956Val) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000186 in 1,613,758 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 11/19 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. M32956T) has been classified as Uncertain significance.
TTN (HGNC:12403): (titin) This gene encodes a large abundant protein of striated muscle. The product of this gene is divided into two regions, a N-terminal I-band and a C-terminal A-band. The I-band, which is the elastic part of the molecule, contains two regions of tandem immunoglobulin domains on either side of a PEVK region that is rich in proline, glutamate, valine and lysine. The A-band, which is thought to act as a protein-ruler, contains a mixture of immunoglobulin and fibronectin repeats, and possesses kinase activity. An N-terminal Z-disc region and a C-terminal M-line region bind to the Z-line and M-line of the sarcomere, respectively, so that a single titin molecule spans half the length of a sarcomere. Titin also contains binding sites for muscle associated proteins so it serves as an adhesion template for the assembly of contractile machinery in muscle cells. It has also been identified as a structural protein for chromosomes. Alternative splicing of this gene results in multiple transcript variants. Considerable variability exists in the I-band, the M-line and the Z-disc regions of titin. Variability in the I-band region contributes to the differences in elasticity of different titin isoforms and, therefore, to the differences in elasticity of different muscle types. Mutations in this gene are associated with familial hypertrophic cardiomyopathy 9, and autoantibodies to titin are produced in patients with the autoimmune disease scleroderma. [provided by RefSeq, Feb 2012]
TTN-AS1 (HGNC:44124): (TTN antisense RNA 1) This gene encodes a non-coding RNA transcribed from the opposite strand to the titin gene. [provided by RefSeq, Aug 2016]
Uncertain significance, criteria provided, single submitter
clinical testing
Revvity Omics, Revvity
Jan 28, 2021
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Uncertain significance, no assertion criteria provided
clinical testing
Diagnostic Laboratory, Department of Genetics, University Medical Center Groningen
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Uncertain significance, no assertion criteria provided
clinical testing
Genome Diagnostics Laboratory, University Medical Center Utrecht
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not specified Uncertain:2
Uncertain significance, criteria provided, single submitter
clinical testing
Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine
May 01, 2014
The Met30388Val variant in TTN has not been previously reported in individuals w ith cardiomyopathy or in large population studies. Computational prediction tool s and conservation analysis do not provide strong support for or against an impa ct to the protein. In summary, the clinical significance of this variant is unce rtain. -
Uncertain significance, criteria provided, single submitter
clinical testing
ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories
Mar 01, 2019
The TTN c.91162A>G; p.Met30388Val variant (rs727503538; ClinVar Variation ID: 165678) is rare in the general population (<1% allele frequency in the Genome Aggregation Database) and has not been reported in the medical literature in association with dilated cardiomyopathy (DCM) or other TTN-related disease. The clinical relevance of rare missense variants in this gene, which are identified on average once per individual sequenced in affected populations (Herman 2012), is not well understood. Yet, evidence suggests that the vast majority of such missense variants do not contribute to the clinical outcome of DCM (Begay 2015). Thus, the clinical significance of the p.Met30388Val variant cannot be determined with certainty. -
TTN-related disorder Uncertain:1
Uncertain significance, criteria provided, single submitter
clinical testing
PreventionGenetics, part of Exact Sciences
Oct 11, 2022
The TTN c.98866A>G variant is predicted to result in the amino acid substitution p.Met32956Val. To our knowledge, this variant has not been reported in the literature. This variant is reported in 0.010% of alleles in individuals of East Asian descent in gnomAD (http://gnomad.broadinstitute.org/variant/2-179403796-T-C). At this time, the clinical significance of this variant is uncertain due to the absence of conclusive functional and genetic evidence. -
Autosomal recessive limb-girdle muscular dystrophy type 2J;C1858763:Dilated cardiomyopathy 1G Uncertain:1
Uncertain significance, criteria provided, single submitter
clinical testing
Invitae
Dec 25, 2016
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Autosomal recessive limb-girdle muscular dystrophy type 2J;C1838244:Tibial muscular dystrophy;C1858763:Dilated cardiomyopathy 1G;C1861065:Hypertrophic cardiomyopathy 9;C1863599:Myopathy, myofibrillar, 9, with early respiratory failure;C2673677:Early-onset myopathy with fatal cardiomyopathy Uncertain:1
Uncertain significance, criteria provided, single submitter
clinical testing
Fulgent Genetics, Fulgent Genetics
Oct 31, 2018
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Cardiovascular phenotype Benign:1
Likely benign, criteria provided, single submitter
clinical testing
Ambry Genetics
Mar 26, 2020
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. -