chr2-178667239-C-A

Variant names:

Variant summary

Our verdict is Pathogenic. Variant got 16 ACMG points: 16P and 0B. PVS1PP5_Very_Strong

The NM_001267550.2(TTN):c.35794G>T(p.Glu11932*) variant causes a stop gained change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000188 in 1,596,686 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 0.000020 ( 0 hom., cov: 32)

Exomes 𝑓: 0.000019 ( 0 hom. )

Consequence

TTN
NM_001267550.2 stop_gained

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:6U:1

Conservation

PhyloP100: -1.82

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: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]

TTN-AS1 links:

LOC124906100 (HGNC:):

LOC124906100 links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Pathogenic. Variant got 16 ACMG points.

PVS1

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

PP5

Variant 2-178667239-C-A is Pathogenic according to our data. Variant chr2-178667239-C-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 238750.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr2-178667239-C-A is described in Lovd as [Pathogenic]. Variant chr2-178667239-C-A is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTN	NM_001267550.2 link	c.35794G>T	p.Glu11932*	stop_gained	Exon 162 of 363	ENST00000589042.5	NP_001254479.2	A0A0A0MTS7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5 link	c.35794G>T	p.Glu11932*	stop_gained	Exon 162 of 363	5	NM_001267550.2	ENSP00000467141.1		A0A0A0MTS7

Frequencies

GnomAD3 genomes

AF:

0.0000197

AC:

AN:

152040

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:

0.0000441

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.00000916

AC:

AN:

218240

Hom.:

AF XY:

0.00000839

AC XY:

AN XY:

119136

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:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.0000212

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000187

AC:

AN:

1444646

Hom.:

Cov.:

AF XY:

0.0000153

AC XY:

AN XY:

716992

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:

0.0000245

Gnomad4 OTH exome

AF:

0.00

GnomAD4 genome

AF:

0.0000197

AC:

AN:

152040

Hom.:

Cov.:

AF XY:

0.0000135

AC XY:

AN XY:

74264

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:

0.0000441

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.0000508

Hom.:

Bravo

AF:

0.0000189

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:6Uncertain:1

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

not provided

Pathogenic:2Uncertain:1

Aug 01, 2018

CeGaT Center for Human Genetics Tuebingen

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Feb 06, 2018

Eurofins Ntd Llc (ga)

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Nov 15, 2021

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Observed with a splice variant on the opposite allele (in trans) in a patient with a congenital TTN-related disorder in published literature (Oates et al., 2018); Nonsense variant predicted to result in protein truncation or nonsense mediated decay; Not observed at a significant frequency in large population cohorts (Lek et al., 2016); This variant is associated with the following publications: (PMID: 32778822, 29691892) -

Autosomal recessive limb-girdle muscular dystrophy type 2J

Pathogenic:1

Feb 01, 2022

MGZ Medical Genetics Center

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

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

Pathogenic:1

Nov 04, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change creates a premature translational stop signal (p.Glu11932*) in the TTN gene. While this is not anticipated to result in nonsense mediated decay, it is expected to create a truncated TTN protein. The frequency data for this variant in the population databases is considered unreliable, as metrics indicate poor data quality at this position in the gnomAD database. This premature translational stop signal has been observed in individual(s) with clinical features of autosomal recessive centronuclear myopathy (PMID: 29691892). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. This variant has been reported in individual(s) with autosomal dominant non-ischemic cardiomyopathy (internal data); however, the role of the variant in this condition is currently unclear. ClinVar contains an entry for this variant (Variation ID: 238750). This variant is located in the I band of TTN (PMID: 25589632). Truncating variants in this region have been reported in individuals affected with autosomal recessive centronuclear myopathy (PMID: 23975875, internal data). Truncating variants in this region have also been identified in individuals affected with autosomal dominant dilated cardiomyopathy and/or cardio-related conditions (PMID: 27869827, 32964742, internal data). For these reasons, this variant has been classified as Pathogenic. -

Early-onset myopathy with fatal cardiomyopathy

Pathogenic:1

Jan 09, 2025

Broad Center for Mendelian Genomics, Broad Institute of MIT and Harvard

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: research

The heterozygous p.Glu11932Ter variant in TTN was identified by our study in one individual with early onset myopathy, in the compound heterozygous state along with another pathogenic variant. The phase of these variants is unknown at this time. The p.Glu11932Ter variant has been reported in 6 families with TTN-related myopathy (PMID: 29691892), and has been identified in 0.003% (30/1171268) of European (non-Finnish) chromosomes by the Genome Aggregation Database (gnomAD, http://gnomad.broadinstitute.org; dbSNP rs878854299). Although this variant has been seen in the general population in a heterozygous state, its frequency is low enough to be consistent with a recessive carrier frequency. Of the 7 affected individuals, 4 were compound heterozygotes that carried a reported pathogenic or likely pathogenic variant in trans, which increases the likelihood that the p.Glu11932Ter variant is pathogenic (Variation ID: 1067510, 2938083, 404786, 223329; PMID: 29691892). This variant has also been reported in ClinVar (Variation ID: 238750) and has been interpreted as pathogenic/likely pathogenic by Labcorp, GeneDx, MGZ Medical Genetics Center, and CeGaT Center for Human Genetics Tuebingen, and as a variant of uncertain significance by Eurofins Ntd Llc. This nonsense variant leads to a premature termination codon at position 11932 which is predicted to lead to a truncated or absent protein. Loss of function of the TTN gene is an established disease mechanism in autosomal recessive TTN-related myopathy. In summary, this variant meets criteria to be classified as pathogenic for autosomal recessive TTN-related myopathy. ACMG/AMP Criteria applied: PM3_very-strong, PVS1, PM2_supporting (Richards 2015). -

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

Pathogenic:1

May 28, 2024

Fulgent Genetics, Fulgent Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Pathogenic

0.36

BayesDel_noAF

Pathogenic

0.28

CADD

Pathogenic

DANN

Uncertain

0.99

Eigen

Benign

-0.11

Eigen_PC

Benign

-0.40

FATHMM_MKL

Benign

0.10

Vest4

0.74

GERP RS

0.21

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.050

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