2-178546049-C-G

Position:

• chr2-178546049-C-G

Variant summary

Our verdict is Pathogenic. Variant got 15 ACMG points: 15P and 0B. PM5 PP2 PP3_Strong PP5_Very_Strong

The NM_001267550.2(TTN):​c.95187G>C​(p.Trp31729Cys) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000616 in 1,461,442 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 (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. W31729L) has been classified as Pathogenic.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000062 (0 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:5
• Conservation: PhyloP100: 7.91

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-AS1 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 15 ACMG points.

• PM5: Other missense variant is known to change same aminoacid residue: Variant chr2-178546050-C-A is described in Lovd as [Pathogenic].
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), TTN. . Gene score misZ -1.1021 (greater than the threshold 3.09). Trascript score misZ 6.9794 (greater than threshold 3.09). GenCC has associacion of gene with dilated cardiomyopathy, tibial muscular dystrophy, early-onset myopathy with fatal cardiomyopathy, autosomal recessive centronuclear myopathy, hypertrophic cardiomyopathy, hypertrophic cardiomyopathy 9, TTN-related myopathy, dilated cardiomyopathy 1G, arrhythmogenic right ventricular cardiomyopathy, myopathy, myofibrillar, 9, with early respiratory failure, familial isolated dilated cardiomyopathy, childhood-onset progressive contractures-limb-girdle weakness-muscle dystrophy syndrome, autosomal recessive limb-girdle muscular dystrophy type 2J.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.983
• PP5: Variant 2-178546049-C-G is Pathogenic according to our data. Variant chr2-178546049-C-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 132136.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr2-178546049-C-G is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTN	NM_001267550.2	c.95187G>C	p.Trp31729Cys	missense_variant	343/363	ENST00000589042.5	NP_001254479.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.95187G>C	p.Trp31729Cys	missense_variant	343/363	5	NM_001267550.2	ENSP00000467141.1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.00000616 AC: 9 AN: 1461442 Hom.: 0 Cov.: 33 AF XY: 0.00000688 AC XY: 5 AN XY: 727006

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: 0.00000810

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:5

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:3

Likely pathogenic, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Sep 12, 2019	- -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Oct 20, 2021	Reported previously as W30088C in association with autosomal dominant hereditary myopathy with early respiratory failure (HMERF) (Palmio et al., 2014); Functional studies indicate the variant impairs the domain solubility and prevents proper protein folding (Hedberg et al., 2014); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Not observed at significant frequency in large population cohorts (gnomAD); This variant is associated with the following publications: (PMID: 24980681, 24575448, 24636144, 29382405, 30666435, 23606733, 29997562) -
Likely pathogenic, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Oct 26, 2017	- -

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

Aug 29, 2022

ClinVar contains an entry for this variant (Variation ID: 132136). This variant is also known as g.274428G>C (p.W30088C) and c.87483G>C (p.Trp29161Cys). This missense change has been observed in individuals with hereditary myopathy with early respiratory failure (HMERF) (PMID: 23606733, 29382405, 29997562, 30666435). This variant is not present in population databases (gnomAD no frequency). This sequence change replaces tryptophan, which is neutral and slightly polar, with cysteine, which is neutral and slightly polar, at codon 31729 of the TTN protein (p.Trp31729Cys). For these reasons, this variant has been classified as Pathogenic. This variant is located in the A band of TTN (PMID: 25589632). Variants in this region may be relevant for cardiac or neuromuscular disorders (PMID: 25589632, 23975875). Experimental studies have shown that this missense change affects TTN function (PMID: 24636144). Algorithms developed to predict the effect of variants on protein structure and function are not available or were not evaluated for this variant. -

Myopathy, myofibrillar, 9, with early respiratory failure Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

GeneReviews

Feb 27, 2014

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.28	D
BayesDel_noAF	Pathogenic	0.17
CADD	Benign	23
DANN	Benign	0.96
Eigen	Pathogenic	1.2
Eigen_PC	Pathogenic	1.0
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.94	D;D;D;.;D;D;D
M_CAP	Pathogenic	0.91	D
MetaRNN	Pathogenic	0.98	D;D;D;D;D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	4.1	.;.;.;H;.;.;H
PrimateAI	Uncertain	0.74	T
PROVEAN	Pathogenic	-9.9	D;D;.;.;D;D;.
REVEL	Pathogenic	0.96
Sift	Pathogenic	0.0	D;D;.;.;D;D;.
Polyphen		1.0	.;.;.;D;.;.;D
Vest4		0.63
MutPred		0.88		.;.;.;Loss of catalytic residue at A30087 (P = 0.0477);.;.;Loss of catalytic residue at A30087 (P = 0.0477);
MVP		0.91
MPC		0.58
ClinPred		1.0	D
GERP RS		5.8

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

Other links and lift over

dbSNP: rs869320742; hg19: chr2-179410776;