2-178587304-C-T

Variant names:

• chr2-178587304-C-T
• rs372812312
• NM_001267550.2:c.63907G>A

Variant summary

Our verdict is Likely benign. The variant received -3 ACMG points: 0P and 3B. BP4_Moderate BP6

The NM_001267550.2(TTN):​c.63907G>A​(p.Val21303Met) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000732 in 1,612,874 control chromosomes in the GnomAD database, including 1 homozygotes. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: 𝑓 0.000033 (0 hom., cov: 32)
  • Exomes 𝑓: 0.000077 (1 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:10 B:4
• Conservation: PhyloP100: 1.40
• Publications: 2 publications found

Genes affected

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]

ACMG classification

Our verdict: Likely_benign. The variant received -3 ACMG points.

• BP4: Computational evidence support a benign effect (MetaRNN=0.16765162).
• BP6: Variant 2-178587304-C-T is Benign according to our data. Variant chr2-178587304-C-T is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 467367.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTN	NM_001267550.2	c.63907G>A	p.Val21303Met	missense_variant	Exon 307 of 363	ENST00000589042.5	NP_001254479.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.63907G>A	p.Val21303Met	missense_variant	Exon 307 of 363	5	NM_001267550.2	ENSP00000467141.1

Frequencies

GnomAD3 genomes AF: 0.0000329 AC: 5 AN: 151970 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000242

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.000207

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000441

Gnomad OTH AF: 0.00

GnomAD2 exomes AF: 0.0000889 AC: 22 AN: 247532 AF XY: 0.000104

Gnomad AFR exome AF: 0.000129

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.000499

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000537

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000773 AC: 113 AN: 1460904 Hom.: 1 Cov.: 33 AF XY: 0.0000949 AC XY: 69 AN XY: 726746

African (AFR) AF: 0.0000898 AC: 3 AN: 33426

American (AMR) AF: 0.00 AC: 0 AN: 44680

Ashkenazi Jewish (ASJ) AF: 0.000536 AC: 14 AN: 26118

East Asian (EAS) AF: 0.00 AC: 0 AN: 39480

South Asian (SAS) AF: 0.000313 AC: 27 AN: 86242

European-Finnish (FIN) AF: 0.0000375 AC: 2 AN: 53374

Middle Eastern (MID) AF: 0.000174 AC: 1 AN: 5754

European-Non Finnish (NFE) AF: 0.0000531 AC: 59 AN: 1111504

Other (OTH) AF: 0.000116 AC: 7 AN: 60326

GnomAD4 genome AF: 0.0000329 AC: 5 AN: 151970 Hom.: 0 Cov.: 32 AF XY: 0.0000539 AC XY: 4 AN XY: 74198

African (AFR) AF: 0.0000242 AC: 1 AN: 41398

American (AMR) AF: 0.00 AC: 0 AN: 15250

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3472

East Asian (EAS) AF: 0.00 AC: 0 AN: 5156

South Asian (SAS) AF: 0.000207 AC: 1 AN: 4824

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10596

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 316

European-Non Finnish (NFE) AF: 0.0000441 AC: 3 AN: 67964

Other (OTH) AF: 0.00 AC: 0 AN: 2082

Alfa AF: 0.000165 Hom.: 0

Bravo AF: 0.0000604

ESP6500AA AF: 0.000260 AC: 1

ESP6500EA AF: 0.000121 AC: 1

ExAC AF: 0.0000745 AC: 9

EpiCase AF: 0.00

EpiControl AF: 0.0000593

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:10 Benign:4

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Uncertain:5 Benign:1

-

Genome Diagnostics Laboratory, Amsterdam University Medical Center

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Dec 23, 2019

GeneDx

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Jul 01, 2024

CeGaT Center for Human Genetics Tuebingen

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

TTN: PM2:Supporting, BP4 -

-

Clinical Genetics, Academic Medical Center

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Sep 28, 2023

ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The TTN c.63907G>A; p.Val21303Met variant (rs372812312; ClinVar Variation ID: 467367) is rare in the general population (<0.2% 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.Val21303Met variant cannot be determined with certainty. References: Begay RL et al. Role of Titin Missense Variants in Dilated Cardiomyopathy. J Am Heart Assoc. 2015 Nov 13;4(11). PMID: 26567375. Herman DS et al. Truncations of titin causing dilated cardiomyopathy. N Engl J Med. 2012 Feb 16;366(7):619-28. PMID: 22335739. Linke WA and Hamdani N. Gigantic business: titin properties and function through thick and thin. Circ Res 2014; 114(6): 1052-1068. PMID: 24625729. -

Oct 18, 2016

Eurofins Ntd Llc (ga)

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

not specified Uncertain:1

Aug 03, 2022

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: TTN c.56203G>A (p.Val18735Met) results in a conservative amino acid change located in the A-band region of the encoded protein sequence. Three of four in-silico tools predict a benign effect of the variant on protein function. The variant allele was found at a frequency of 8.9e-05 in 247532 control chromosomes (gnomAD). To our knowledge, no occurrence of c.56203G>A in individuals affected with Limb-Girdle Muscular Dystrophy, Type 2J and no experimental evidence demonstrating its impact on protein function have been reported. Two ClinVar submitters (evaluation after 2014) cite the variant as benign/likely benign and four ClinVar submitters (evaluation after 2014) cite it as uncertain significance. Based on the evidence outlined above, the variant was classified as uncertain significance. -

Autosomal recessive limb-girdle muscular dystrophy type 2J Uncertain:1

Jan 13, 2018

Illumina Laboratory Services, Illumina

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Autosomal recessive limb-girdle muscular dystrophy type 2J;C1858763:Dilated cardiomyopathy 1G Uncertain:1

Jun 03, 2017

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Dilated cardiomyopathy 1G Uncertain:1

Jan 13, 2018

Illumina Laboratory Services, Illumina

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Early-onset myopathy with fatal cardiomyopathy Uncertain:1

Jan 13, 2018

Illumina Laboratory Services, Illumina

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Tibial muscular dystrophy Benign:1

Jan 13, 2018

Illumina Laboratory Services, Illumina

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score and internal cut-off values, a variant classified as benign is not then subjected to further curation. The score for this variant resulted in a classification of benign for this disease. -

Myopathy, myofibrillar, 9, with early respiratory failure Benign:1

Jan 13, 2018

Illumina Laboratory Services, Illumina

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score and internal cut-off values, a variant classified as benign is not then subjected to further curation. The score for this variant resulted in a classification of benign for this disease. -

Cardiovascular phenotype Benign:1

Mar 25, 2020

Ambry Genetics

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.40
BayesDel_addAF	Benign	-0.20	T
BayesDel_noAF	Benign	-0.22
CADD	Benign	21
DANN	Uncertain	0.98
Eigen	Uncertain	0.40
Eigen_PC	Uncertain	0.42
FATHMM_MKL	Uncertain	0.84	D
LIST_S2	Uncertain	0.91	D;D;D;.;D;D;D
M_CAP	Benign	0.036	D
MetaRNN	Benign	0.17	T;T;T;T;T;T;T
MetaSVM	Benign	-0.46	T
MutationAssessor	Pathogenic	3.5	.;.;.;M;.;.;M
PhyloP100		1.4
PrimateAI	Benign	0.46	T
PROVEAN	Benign	-2.1	N;N;.;.;N;N;.
REVEL	Uncertain	0.37
Sift	Uncertain	0.0030	D;D;.;.;D;D;.
Polyphen		0.84	.;.;.;P;.;.;P
Vest4		0.44
MVP		0.57
MPC		0.14
ClinPred		0.21	T
GERP RS		5.1
Mutation Taster		=96/4	polymorphism

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs372812312; hg19: chr2-179452031; COSMIC: COSV59957710; COSMIC: COSV59957710;