Our verdict is Benign. Variant got -15 ACMG points: 1P and 16B. PP2BP4_StrongBP6_Very_StrongBS1
The NM_001267550.2(TTN):āc.66977A>Gā(p.Lys22326Arg) variant causes a missense change. The variant allele was found at a frequency of 0.000302 in 1,613,306 control chromosomes in the GnomAD database, including 2 homozygotes. In-silico tool predicts a benign outcome for this variant. 13/19 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Likely benign (ā ā ). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. K22326E) has been classified as Likely benign.
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]
Missense variant where missense usually causes diseases, TTN
BP4
Computational evidence support a benign effect (MetaRNN=0.006349772).
BP6
Variant 2-178580402-T-C is Benign according to our data. Variant chr2-178580402-T-C is described in ClinVar as [Likely_benign]. Clinvar id is 47245.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr2-178580402-T-C is described in Lovd as [Benign]. Variant chr2-178580402-T-C is described in Lovd as [Likely_benign].
BS1
Variant frequency is greater than expected in population afr. gnomad4 allele frequency = 0.00163 (248/152220) while in subpopulation AFR AF= 0.00565 (235/41584). AF 95% confidence interval is 0.00506. There are 1 homozygotes in gnomad4. There are 123 alleles in male gnomad4 subpopulation. Median coverage is 33. This position pass quality control queck.
Likely benign, criteria provided, single submitter
clinical testing
Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine
Apr 10, 2012
Lys19758Arg in exon 266 of TTN: This variant is not expected to have clinical si gnificance because it has been identified in 0.4% (12/3048) of African American chromosomes from a broad population by the NHLBI Exome Sequencing Project (http: //evs.gs.washington.edu/EVS). Lys19758Arg in exon 266 of TTN (allele frequenc y = 0.4%, 12/3048) ** -
Benign, no assertion criteria provided
clinical testing
Clinical Genetics, Academic Medical Center
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Benign, criteria provided, single submitter
clinical testing
Athena Diagnostics
Feb 19, 2020
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Likely benign, criteria provided, single submitter
clinical testing
Eurofins Ntd Llc (ga)
Nov 12, 2015
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Benign, criteria provided, single submitter
clinical testing
Women's Health and Genetics/Laboratory Corporation of America, LabCorp
Nov 29, 2021
Variant summary: TTN c.59273A>G (p.Lys19758Arg) results in a conservative amino acid change located in the A-band region of the encoded protein sequence. Four of five in-silico tools predict a benign effect of the variant on protein function. The variant allele was found at a frequency of 0.00049 in 279656 control chromosomes, predominantly at a frequency of 0.0053 within the African or African-American subpopulation in the gnomAD database, including 2 homozygotes. The observed variant frequency within African or African-American control individuals in the gnomAD database is approximately 13.5-fold of the estimated maximal expected allele frequency for a pathogenic variant in TTN causing Dilated Cardiomyopathy phenotype (0.00039), strongly suggesting that the variant is a benign polymorphism found primarily in populations of African or African-American origin. c.59273A>G has been reported in the literature in an African American individual affected with Dilated Cardiomyopathy (Pugh_2014). This report does not provide unequivocal conclusions about association of the variant with Dilated Cardiomyopathy. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. Four clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation. All laboratories classified the variant as benign (n=2) / likely benign (n=2). Based on the evidence outlined above, the variant was classified as benign. -
not provided Benign:4
Likely benign, criteria provided, single submitter
clinical testing
CeGaT Center for Human Genetics Tuebingen
Dec 01, 2023
TTN: BP4, BS2 -
Likely benign, criteria provided, single submitter
clinical testing
GeneDx
Sep 18, 2020
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Likely benign, no assertion criteria provided
clinical testing
Joint Genome Diagnostic Labs from Nijmegen and Maastricht, Radboudumc and MUMC+
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Likely benign, no assertion criteria provided
clinical testing
Clinical Genetics DNA and cytogenetics Diagnostics Lab, Erasmus MC, Erasmus Medical Center
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Autosomal recessive limb-girdle muscular dystrophy type 2J Benign:1
Benign, criteria provided, single submitter
clinical testing
Genome-Nilou Lab
Sep 10, 2021
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Autosomal recessive limb-girdle muscular dystrophy type 2J;C1858763:Dilated cardiomyopathy 1G Benign:1
Benign, criteria provided, single submitter
clinical testing
Invitae
Jan 20, 2024
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Early-onset myopathy with fatal cardiomyopathy Benign:1
Benign, criteria provided, single submitter
clinical testing
Genome-Nilou Lab
Sep 10, 2021
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Tibial muscular dystrophy Benign:1
Benign, criteria provided, single submitter
clinical testing
Genome-Nilou Lab
Sep 10, 2021
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Myopathy, myofibrillar, 9, with early respiratory failure Benign:1
Benign, criteria provided, single submitter
clinical testing
Genome-Nilou Lab
Sep 10, 2021
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Cardiovascular phenotype Benign:1
Likely benign, criteria provided, single submitter
clinical testing
Ambry Genetics
Nov 14, 2018
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. -