rs371678190

Positions:

Variant summary

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

The NM_001267550.2(TTN):c.68449C>T(p.Arg22817*) variant causes a stop gained change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000031 in 1,613,036 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: 32)

Exomes 𝑓: 0.0000027 ( 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: 1.74

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 2-178578066-G-A is Pathogenic according to our data. Variant chr2-178578066-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 165869.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTN	NM_001267550.2 linkuse as main transcript	c.68449C>T	p.Arg22817*	stop_gained	322/363	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.68449C>T	p.Arg22817*	stop_gained	322/363	5	NM_001267550.2	ENSP00000467141.1		A0A0A0MTS7

Frequencies

GnomAD3 genomes

AF:

0.00000658

AC:

AN:

151994

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

GnomAD3 exomes

AF:

0.00000403

AC:

AN:

248048

Hom.:

AF XY:

0.00000743

AC XY:

AN XY:

134566

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad SAS exome

AF:

0.0000327

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000274

AC:

AN:

1461042

Hom.:

Cov.:

AF XY:

0.00000550

AC XY:

AN XY:

726800

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:

0.0000116

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

0.00000180

Gnomad4 OTH exome

AF:

0.0000166

GnomAD4 genome

AF:

0.00000658

AC:

AN:

151994

Hom.:

Cov.:

AF XY:

0.0000135

AC XY:

AN XY:

74226

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

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

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

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Dec 30, 2023

This sequence change creates a premature translational stop signal (p.Arg22817*) 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 present in population databases (rs371678190, gnomAD 0.003%). This premature translational stop signal has been observed in individuals with clinical features of dilated cardiomyopathy (PMID: 28045975; Invitae). ClinVar contains an entry for this variant (Variation ID: 165869). 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). For these reasons, this variant has been classified as Pathogenic. -

Dilated cardiomyopathy 1G

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

MGZ Medical Genetics Center

Dec 29, 2021

- -

Cardiomyopathy

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

CHEO Genetics Diagnostic Laboratory, Children's Hospital of Eastern Ontario

Oct 27, 2017

- -

Primary familial dilated cardiomyopathy

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Molecular Diagnostic Laboratory for Inherited Cardiovascular Disease, Montreal Heart Institute

- -

not provided

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Aug 11, 2023

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; Not observed at significant frequency in large population cohorts (gnomAD); Located in the A-band region of TTN in which the majority of loss of function variants have been associated with autosomal dominant titinopathies (Herman et al., 2012); This variant is associated with the following publications: (PMID: 28045975, 28255936, 22335739) -

Primary dilated cardiomyopathy

Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Mar 19, 2015

The p.Arg20249X variant in TTN has not been previously reported in any other fam ilies with cardiomyopathy or in large population studies. This nonsense variant leads to a premature termination codon at position 20249, which is predicted to lead to a truncated or absent protein. Nonsense and other truncating variants in TTN are strongly associated with DCM, particularly if they are located in the e xons encoding for the A-band region of the protein (Herman 2012, Pugh 2014), whe re this variant is located. In summary, although additional studies are required to fully establish its clinical significance, the Arg20249X variant is likely p athogenic. -

Cardiovascular phenotype

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Mar 04, 2024

The p.R13752* pathogenic mutation (also known as c.41254C>T), located in coding exon 149 of the TTN gene, results from a C to T substitution at nucleotide position 41254. This changes the amino acid from an arginine to a stop codon within coding exon 149. 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 alteration has been reported in both sudden death and dilated cardiomyopathy (DCM) cohorts (also reported as p.R20249* (c.60745C>T) and p.R22817* (c.68449C>T)) (Franaszczyk M et al. PLoS ONE, 2017 Jan;12:e0169007; Campuzano O et al. Sports Med, 2017 Oct;47:2101-2115). This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). In addition to the clinical data presented in the literature, 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 Jan;49:46-53). This alteration is expected to result in loss of function by premature protein truncation or nonsense-mediated mRNA decay. 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

0.52

BayesDel_noAF

Pathogenic

0.60

CADD

Pathogenic

DANN

Benign

0.97

Eigen

Pathogenic

0.76

Eigen_PC

Uncertain

0.56

FATHMM_MKL

Uncertain

0.90

Vest4

0.96

GERP RS

1.4

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.080

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