2-178546476-G-A

Position:

chr2-178546476-G-A

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1PM2PP5_Very_Strong

The NM_001267550.2(TTN):c.94855C>T(p.Arg31619*) variant causes a stop gained change. The variant allele was found at a frequency of 0.00000248 in 1,612,500 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★). Variant results in nonsense mediated mRNA decay.

Frequency

Genomes: 𝑓 0.0000066 ( 0 hom., cov: 33)

Exomes 𝑓: 0.0000021 ( 0 hom. )

Consequence

TTN
NM_001267550.2 stop_gained

Scores

Clinical Significance

Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:7

Conservation

PhyloP100: 4.18

Variant links:

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 links:

TTN-AS1 (HGNC:):

TTN-AS1 links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Pathogenic. Variant got 18 ACMG points.

PVS1

Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.

PM2

Very rare variant in population databases, with high coverage;

PP5

Variant 2-178546476-G-A is Pathogenic according to our data. Variant chr2-178546476-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 223389.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr2-178546476-G-A is described in Lovd as [Likely_pathogenic]. Variant chr2-178546476-G-A is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTN	NM_001267550.2 linkuse as main transcript	c.94855C>T	p.Arg31619*	stop_gained	342/363	ENST00000589042.5	NP_001254479.2	A0A0A0MTS7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5 linkuse as main transcript	c.94855C>T	p.Arg31619*	stop_gained	342/363	5	NM_001267550.2	ENSP00000467141.1		A0A0A0MTS7

Frequencies

GnomAD3 genomes

AF:

0.00000657

AC:

AN:

152130

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.0000147

Gnomad OTH

AF:

0.00

GnomAD4 exome

AF:

0.00000205

AC:

AN:

1460370

Hom.:

Cov.:

AF XY:

0.00000275

AC XY:

AN XY:

726300

show subpopulations

Gnomad4 AFR exome

AF:

0.00

Gnomad4 AMR exome

AF:

0.00

Gnomad4 ASJ exome

AF:

0.00

Gnomad4 EAS exome

AF:

0.00

Gnomad4 SAS exome

AF:

0.00

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

0.00000270

Gnomad4 OTH exome

AF:

0.00

GnomAD4 genome

AF:

0.00000657

AC:

AN:

152130

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

74310

show subpopulations

Gnomad4 AFR

AF:

0.00

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.0000147

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.0000301

Hom.:

Bravo

AF:

0.00000378

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:7

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

not provided

Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Dec 14, 2022	Identified in a cohort of DCM patients; no clinical or segregation data available (Roberts et al., 2015); Nonsense variant predicted to result in protein truncation or nonsense mediated decay in a gene for which loss-of-function is a known mechanism of disease; Located in the A-band region of titin, where the majority of truncating pathogenic variants associated with DCM have been reported (Herman et al., 2012); Not observed in large population cohorts (gnomAD); This variant is associated with the following publications: (PMID: 25589632, 35177841) -
Likely pathogenic, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Aug 01, 2024	TTN: PVS1:Strong, PM2, PS4:Moderate -

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

Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Dec 03, 2023

This sequence change creates a premature translational stop signal (p.Arg31619*) in the TTN gene. While this is not anticipated to result in nonsense mediated decay, it is expected to create a truncated TTN protein. This variant is not present in population databases (gnomAD no frequency). This premature translational stop signal has been observed in individual(s) with dilated cardiomyopathy (PMID: 25589632). ClinVar contains an entry for this variant (Variation ID: 223389). This variant is located in the A band of TTN (PMID: 25589632). Truncating variants in this region are significantly overrepresented in patients affected with dilated cardiomyopathy (PMID: 25589632). Truncating variants in this region have also been reported in individuals affected with autosomal recessive centronuclear myopathy (PMID: 23975875). In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -

Dilated cardiomyopathy 1G

Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Victorian Clinical Genetics Services, Murdoch Childrens Research Institute

May 21, 2020

Based on the classification scheme VCGS_Germline_v1.1.1, this variant is classified as likely pathogenic. Following criteria are met: 0102 - Loss-of-function is a known mechanism of disease for this gene. (N) 0104 - Dominant Negative is a mechanism of disease for this gene. (N) 0108 - This gene is known to be associated with both recessive and dominant disease. Autosomal recessive for limb-girdle muscular dystrophy and autosomal dominant for familial hypertrophic cardiomyopathy, myofibrillar myopathy and tibial muscular dystrophy. (OMIM). (N) 0112 - Variants in this gene are known to have reduced penetrance (Franaszczyk, M. et al. (2017)). (N) 0201 - Variant is predicted to cause nonsense-mediated decay (NMD) and loss of protein. (P) 0251 - Variant is heterozygous. (N) 0301 - Variant is absent from gnomAD. (P) 0507 - Identified variant type is not compatible with in-silico predictions of pathogenicity. (N) 0602 - Variant is located in a hotspot region or cluster of pathogenic variants. TTN A-band, PSI=1 (Roberts, A. et al. (2015)) (P) 0703 - Comparable variants have moderate previous evidence for pathogenicity. All TTN truncating variants in this region are likely pathogenic or pathogenic. (ClinVar, Decipher) (P) 0803 - Low previous evidence of pathogenicity in unrelated individuals. Reported as likely pathogenic in a DCM proband (Roberts, A. et al. (2015)) (P) 0905 - No segregation evidence has been identified for this variant. (N) 1007 - No published functional evidence has been identified for this variant. (N) 1208 - Inheritance information for this variant is not currently available. (N) Legend: (P) - Pathogenic, (N) - Neutral, (B) - Benign -

Dilated cardiomyopathy 1G;C1861065:Hypertrophic cardiomyopathy 9

Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

New York Genome Center

Jan 23, 2023

The c.94855C>T p.(Arg31619Ter) variant in the TTN gene has previously been deposited in ClinVar [ClinVar ID: 223389] as Likely Pathogenic/Pathogenic and has been reported in 3 affected individuals with dilated cardiomyopathy or atrial fibrillation in the literature [PMID:25589632, 28611029,35177841]. The c.94855C>T variant is observed in 1 allele (~0.0003% minor allele frequency with 0 homozygotes) in population databases (gnomAD v2.1.1 and v3.1.2,TOPMed Freeze 8), suggesting it is not a common benign variant in the populations represented in those databases. The c.94855C>T variant in TTN is located inexon 342 of this 363-exon gene, predicted to incorporate a premature termination codon (p.(Arg31619Ter)), and is expected to result in loss-of-function either through protein truncation or nonsense-mediated mRNA decay. The p.(Arg31619Ter) residue is within the A-band of TTN, where most variants associated with dilated cardiomyopathy are located [PMID:26777568, 27869827, 28045975]. Based on available evidence, this c.94855C>T p.(Arg31619Ter) variant identified in the TTN gene is classified as Likely Pathogenic. -

Primary dilated cardiomyopathy

Pathogenic:1

Likely pathogenic, criteria provided, single submitter

research

Cardiovascular Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust

Oct 08, 2014

This TTN truncating variant (TTNtv) was identified in one individual in this cohort and is located in an exon that is highly expressed in the heart. In the seven cohorts assessed, TTNtv were found in 14% of ambulant DCM, 22% end-stage or familial DCM, and 2% controls. Heterozygous nonsense, frameshift and canonical splice-disrupting variants found in constitutive and other highly utilised exons are highly likely to be pathogenic when identified in individuals with phenotypically confirmed DCM. TTNtv found incidentally in healthy individuals (excluding familial assessment of DCM relatives) are thought to have low penetrance, particularly when identified in exons that are not constitutively expressed in the heart. -

Cardiovascular phenotype

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Jun 02, 2022

The p.R22554* pathogenic mutation (also known as c.67660C>T), located in coding exon 169 of the TTN gene, results from a C to T substitution at nucleotide position 67660. This changes the amino acid from an arginine to a stop codon within coding exon 169. This exon is located in the A-band region of the N2-B isoform of the titin protein and is constitutively expressed in TTN transcripts (percent spliced in or PSI 100%). This variant (referred to as p.R31619*, c.94855C>T) has been detected in individuals reported to have dilated cardiomyopathy (Roberts AM et al. Sci Transl Med, 2015 Jan;7:270ra6; Haskell GT et al. Circ Cardiovasc Genet, 2017 Jun;10). This alteration is expected to result in loss of function by premature protein truncation or nonsense-mediated mRNA decay. While truncating variants in TTN are present in 1-3% of the general population, truncating variants in the A-band are the most common cause of dilated cardiomyopathy (DCM) (Herman DS et al. N. Engl. J. Med., 2012 Feb;366:619-28; Roberts AM et al. Sci Transl Med, 2015 Jan;7:270ra6). TTN truncating variants encoded in constitutive exons (PSI >90%) have been found to be significantly associated with DCM regardless of their position in titin (Schafer S et al. Nat. Genet., 2017 01;49:46-53). Based on the supporting evidence, this alteration is interpreted as a disease-causing mutation. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Pathogenic

0.60

BayesDel_noAF

Pathogenic

0.62

CADD

Pathogenic

DANN

Benign

0.96

Eigen

Pathogenic

0.69

Eigen_PC

Uncertain

0.51

FATHMM_MKL

Uncertain

0.91

Vest4

0.97

GERP RS

2.4

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.010

Details are displayed if max score is > 0.2

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

Publications

LitVar

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over