rs397517547

Positions:

chr2-178782872-G-A

Variant summary

Our verdict is Pathogenic. Variant got 11 ACMG points: 11P and 0B. PVS1PM2PP5

The NM_001267550.2(TTN):c.3034C>T(p.Arg1012Ter) variant causes a stop gained change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000205 in 1,461,702 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 Conflicting classifications of pathogenicity (no stars). Variant results in nonsense mediated mRNA decay.

Frequency

Genomes: not found (cov: 32)

Exomes 𝑓: 0.0000021 ( 0 hom. )

Consequence

TTN
NM_001267550.2 stop_gained

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2U:2

Conservation

PhyloP100: 2.60

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:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Pathogenic. Variant got 11 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 2-178782872-G-A is Pathogenic according to our data. Variant chr2-178782872-G-A is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 46899.We mark this variant Likely_pathogenic, oryginal submissions are: {Likely_pathogenic=2, Uncertain_significance=2}. Variant chr2-178782872-G-A is described in Lovd as [Likely_pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTN	NM_001267550.2 linkuse as main transcript	c.3034C>T	p.Arg1012Ter	stop_gained	18/363	ENST00000589042.5	NP_001254479.2
TTN	NM_133379.5 linkuse as main transcript	c.3034C>T	p.Arg1012Ter	stop_gained	18/46	ENST00000360870.10	NP_596870.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5 linkuse as main transcript	c.3034C>T	p.Arg1012Ter	stop_gained	18/363	5	NM_001267550.2	ENSP00000467141	P1
TTN	ENST00000360870.10 linkuse as main transcript	c.3034C>T	p.Arg1012Ter	stop_gained	18/46	5	NM_133379.5	ENSP00000354117		Q8WZ42-6

Frequencies

GnomAD3 genomes

Cov.:

GnomAD3 exomes

AF:

0.00000399

AC:

AN:

250828

Hom.:

AF XY:

0.00

AC XY:

AN XY:

135542

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:

0.00000883

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000205

AC:

AN:

1461702

Hom.:

Cov.:

AF XY:

0.00000275

AC XY:

AN XY:

727154

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

Cov.:

Bravo

AF:

0.00000378

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2Uncertain:2

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

Autosomal recessive limb-girdle muscular dystrophy type 2J

Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

NeuroMeGen, Hospital Clinico Santiago de Compostela

Oct 08, 2018

- -

Primary dilated cardiomyopathy

Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

May 07, 2015

The p.Arg1012X variant in TTN has not been previously reported in individuals wi th cardiomyopathy or in large population studies. This nonsense variant leads to a premature termination codon at position 1012, which is predicted to lead to a truncated or absent protein. Nonsense and other truncating variants in TTN are strongly associated with DCM if they are located in the exons encoding for the A -band (Herman 2012, Pugh 2014) and/or are located in an exon that is highly expr essed in the heart (Roberts 2015). The p.Arg1012X variant is located in the high ly expressed exon 18 in the near Z-disk band. In summary, although additional st udies are required to fully establish its clinical significance, the p.Arg1012X variant is likely pathogenic. -

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

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jan 26, 2023

ClinVar contains an entry for this variant (Variation ID: 46899). This premature translational stop signal has been observed in individual(s) with dilated cardiomyopathy and left ventricular non-compaction (PMID: 24503780, 27532257, 29029073). This variant is present in population databases (rs397517547, gnomAD 0.0009%). This sequence change creates a premature translational stop signal (p.Arg1012*) in the TTN gene. While this is not anticipated to result in nonsense mediated decay, it is expected to create a truncated TTN protein. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. This variant is located in the Z band of TTN (PMID: 25589632). Variants in this region may be clinically relevant, but have not been definitively shown to cause cardiomyopathy or neuromuscular disease (PMID: 27493940, 32778822). -

Cardiovascular phenotype

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Jan 09, 2023

The p.R966* variant (also known as c.2896C>T), located in coding exon 16 of the TTN gene, results from a C to T substitution at nucleotide position 2896. This changes the amino acid from an arginine to a stop codon within coding exon 16. This exon is located in the near Z-disk 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 (referred to as p.Arg1012X, c.3034C>T) was reported in one individual with dilated cardiomyopathy (DCM) who also had variants in other cardiac-related genes (Pugh TJ et al. Genet. Med., 2014 Aug;16:601-8). This alteration is expected to result in loss of function by premature protein truncation or nonsense-mediated mRNA decay. Truncating variants in the A-band of titin are the most common cause of dilated cardiomyopathy (DCM), and, regardless of their position, truncating variants encoded in constitutive exons (PSI >90%) have been found to be significantly associated with 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; Schafer S et al. Nat. Genet., 2017 01;49:46-53). However, TTN truncating variants have also been reported in 1-3% of the general population (Herman DS et al. N. Engl. J. Med. 2012;366:619-28). Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Pathogenic

0.60

BayesDel_noAF

Pathogenic

0.62

CADD

Pathogenic

DANN

Uncertain

1.0

Eigen

Pathogenic

0.86

Eigen_PC

Pathogenic

0.68

FATHMM_MKL

Uncertain

0.91

MutationTaster

Benign

1.0

A;A;A;A;A;A;A

Vest4

0.87

GERP RS

3.0

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.26

Details are displayed if max score is > 0.2

DS_DG_spliceai

0.26

Position offset: 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