rs72646846

Variant summary

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

The NM_001267550.2(TTN):c.61876C>T(p.Arg20626Ter) variant causes a stop gained change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000353 in 1,613,266 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 0.000059 ( 0 hom., cov: 33)

Exomes 𝑓: 0.000033 ( 0 hom. )

Consequence

TTN
NM_001267550.2 stop_gained

Scores

Clinical Significance

Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:14

Conservation

PhyloP100: 3.25

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:

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 2-178589849-G-A is Pathogenic according to our data. Variant chr2-178589849-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 47175.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr2-178589849-G-A is described in Lovd as [Likely_pathogenic]. Variant chr2-178589849-G-A is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTN	NM_001267550.2 linkuse as main transcript	c.61876C>T	p.Arg20626Ter	stop_gained	304/363	ENST00000589042.5
TTN-AS1	NR_038272.1 linkuse as main transcript	n.3189-1290G>A		intron_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTN	ENST00000589042.5 linkuse as main transcript	c.61876C>T	p.Arg20626Ter	stop_gained	304/363	5	NM_001267550.2	P1
TTN-AS1	ENST00000659121.1 linkuse as main transcript	n.417-7747G>A		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes

AF:

0.0000592

AC:

AN:

152024

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00144

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.0000589

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000763

AC:

AN:

248912

Hom.:

AF XY:

0.0000740

AC XY:

AN XY:

135056

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.0000290

Gnomad ASJ exome

AF:

0.00159

Gnomad EAS exome

AF:

0.00

Gnomad SAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00000886

Gnomad OTH exome

AF:

0.000166

GnomAD4 exome

AF:

0.0000328

AC:

AN:

1461242

Hom.:

Cov.:

AF XY:

0.0000371

AC XY:

AN XY:

726904

show subpopulations

Gnomad4 AFR exome

AF:

0.00

Gnomad4 AMR exome

AF:

0.0000224

Gnomad4 ASJ exome

AF:

0.00138

Gnomad4 EAS exome

AF:

0.00

Gnomad4 SAS exome

AF:

0.0000232

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

0.00000270

Gnomad4 OTH exome

AF:

0.0000994

GnomAD4 genome

AF:

0.0000592

AC:

AN:

152024

Hom.:

Cov.:

AF XY:

0.0000943

AC XY:

AN XY:

74250

show subpopulations

Gnomad4 AFR

AF:

0.00

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.00144

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.0000589

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.000163

Hom.:

Bravo

AF:

0.0000680

ExAC

AF:

0.0000662

AC:

EpiCase

AF:

0.00

EpiControl

AF:

0.0000593

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:14

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

not provided

Pathogenic:5

Pathogenic, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Sep 01, 2018	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Jun 14, 2023	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); 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; Also known as p.(Arg18985*) due to the use of an alternate transcript; This variant is associated with the following publications: (PMID: 28798025, 30535219, 31660661, 24980681, 22335739, 30609409, 30536954, 25589632, 24503780, 31514951, 32160020, 32277046, 24119082, 35177841, 23975875) -
Likely pathogenic, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Feb 18, 2016	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Dec 16, 2022	- -
Pathogenic, criteria provided, single submitter	clinical testing	AiLife Diagnostics, AiLife Diagnostics	Jan 27, 2022	- -

Primary dilated cardiomyopathy

Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine	Mar 08, 2019	The p.Arg18058X variant in TTN has been identified in >20 individuals with DCM and segregated with disease in 3 affected individuals from 3 families (Herman 2012, Merlo 2013, unpublished data from GeneDx, Ambry, Invitae, and LMM). It has also been identified in 6 individuals with centronuclear myopathy or who underwent genetic testing for neuromuscular disorders (Elahi 2018, EGL pers. comm., Invitae pers. comm.). This variant has been identified in 0.16% (17/10348) of Ashkenazi Jewish, 1/128284 European, and 1/35320 Latino chromosomes by gnomAD (http://gnomad.broadinstitute.org). Although the frequency in the Ashkenazi Jewish population is higher than expected for a pathogenic variant based on the disease prevalence of DCM, a comparison of the prevalence of this variant in the gnomAD database to DCM patients (LMM data only) shows that it is statistically enriched in the patient population (OR=23.4, p<0.0001). This nonsense variant leads to a premature termination codon at position 18058, which is predicted to lead to a truncated or absent protein. TTN truncating variants located in exons that are highly expressed in the heart are strongly associated with autosomal dominant DCM, particularly if they are located in the A-band, where this variant is located (Herman 2012, Pugh 2014). In addition, TTN variants have also been associated with myopathies and other neuromuscular conditions, which usually have autosomal recessive inheritance (Savarese 2016). In summary, this variant meets criteria to be classified as likely pathogenic for autosomal dominant DCM based on the predicted loss of function impact, enrichment in affected individuals, and segregation studies. ACMG/AMP criteria applied: PVS1_Strong, PP1, PS4_Supporting. -
Pathogenic, criteria provided, single submitter	clinical testing	Knight Diagnostic Laboratories, Oregon Health and Sciences University	Nov 29, 2018	- -

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

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Invitae

Jan 30, 2024

This sequence change creates a premature translational stop signal (p.Arg20626*) 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 (rs72646846, gnomAD 0.2%). This premature translational stop signal has been observed in individual(s) with autosomal recessive congenital myopathy and/or dilated cardiomyopathy (PMID: 22335739, 31660661). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. This variant is also known as c.56953G>A, p.Arg18985*. ClinVar contains an entry for this variant (Variation ID: 47175). 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. -

Cardiomyopathy

Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

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

Jul 23, 2018

- -

Dilated cardiomyopathy 1G

Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Human Genome Sequencing Center Clinical Lab, Baylor College of Medicine

Oct 31, 2019

The c.61876C>T (p.Arg20626Ter) variant in the TTN gene is predicted to introduce a premature translation termination codon and loss of normal protein function. This variant has been reported in two individuals with dilated cardiomyopathy (PMID: 22335739, 24119082). This variant is found in the A-band of TTN. Truncating variants in the A-band of TTN are significantly overrepresented in patients with dilated cardiomyopathy and are considered to be pathogenic for the disease (PMID: 25589632). For these reasons, this variant has been classified as Likely Pathogenic. -

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

Pathogenic, criteria provided, single submitter

clinical testing

Fulgent Genetics, Fulgent Genetics

Oct 09, 2021

- -

Primary familial dilated cardiomyopathy

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

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

Sep 11, 2023

Variant summary: TTN c.54172C>T (p.Arg18058X) results in a premature termination codon, predicted to cause a truncation of the encoded protein or absence of the protein due to nonsense mediated decay, which are commonly known mechanisms for disease. Nonsense, frameshift, and canonical splice-site variants in TTN are strongly associated with DCM when they affect exons encoding for the A-band region (PMIDs: 22335739, 24503780) and/or exons constitutively expressed (proportion spliced in [PSI]>0.9) in the primary cardiac isoforms (PMIDs: 25589632, 31216868, 32964742, 27869827), which is the case forthis variant (A band). The variant allele was found at a frequency of 7.6e-05 in 248912 control chromosomes (gnomAD). This frequency is not significantly higher than estimated for a pathogenic variant in TTN causing Dilated Cardiomyopathy (7.6e-05 vs 0.00039), allowing no conclusion about variant significance. c.54172C>T has been reported in the literature in multiple individuals affected with Dilated Cardiomyopathy (e.g. Herman_2012, Merlo_2013, Morales_2020, Enriquez_2021). These data indicate that the variant is very likely to be associated with disease. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. The following publications have been ascertained in the context of this evaluation (PMID: 34315225, 22335739, 24119082, 32160020). Thirteen ClinVar submitters have assessed the variant since 2014: seven classified the variant as likely pathogenic, and six as pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -

Dilated cardiomyopathy 1A

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Molecular Diagnostic Laboratory for Inherited Cardiovascular Disease, Montreal Heart Institute

Jan 15, 2019

- -

Cardiovascular phenotype

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Aug 10, 2023

The p.R11561* pathogenic mutation (also known as c.34681C>T), located in coding exon 131 of the TTN gene, results from a C to T substitution at nucleotide position 34681. This changes the amino acid from an arginine to a stop codon within coding exon 131. 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 (also reported as c.56953C>T, p.R18985* in the NM_001256850.1 transcript) has been detected in individuals with dilated cardiomyopathy (DCM) and peripartum cardiomyopathy (Herman DS et al. N. Engl. J. Med., 2012 Feb;366:619-28; Merlo M et al. Clin Transl Sci, 2013 Dec;6:424-8; Naftali-Shani N et al Circulation. 2018;138(23):2721-2723), and has also been detected in a left ventricular non-compaction (LVNC) cohort; however, clinical details were limited (Miszalski-Jamka K et al. Circ Cardiovasc Genet, 2017 Aug;10:[Epub ahead of print]). 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 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

0.55

BayesDel_noAF

Pathogenic

0.63

Cadd

Pathogenic

Dann

Uncertain

0.98

Eigen

Pathogenic

0.99

Eigen_PC

Pathogenic

0.84

FATHMM_MKL

Uncertain

0.94

MutationTaster

Benign

1.0

A;A;A;A;A;A

Vest4

0.95

GERP RS

5.2

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.7

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

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