rs267607157

Positions:

• chr2-178785990-G-A

Variant summary

Our verdict is Likely benign. Variant got -1 ACMG points: 1P and 2B. PP2 BP4_Moderate

The NM_001267550.2(TTN):​c.2228C>T​(p.Ala743Val) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000744 in 1,613,954 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 13/18 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★). Synonymous variant affecting the same amino acid position (i.e. A743A) has been classified as Likely benign.

• Frequency:
  • Genomes: 𝑓 0.000013 (0 hom., cov: 32)
  • Exomes 𝑓: 0.0000068 (0 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter P:1 U:1
• Conservation: PhyloP100: 2.94

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]

ACMG classification

Verdict is Likely_benign. Variant got -1 ACMG points.

• 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.
• BP4: Computational evidence support a benign effect (MetaRNN=0.093119025).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTN	NM_001267550.2	c.2228C>T	p.Ala743Val	missense_variant	14/363	ENST00000589042.5	NP_001254479.2
TTN	NM_133379.5	c.2228C>T	p.Ala743Val	missense_variant	14/46	ENST00000360870.10	NP_596870.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.2228C>T	p.Ala743Val	missense_variant	14/363	5	NM_001267550.2	ENSP00000467141	P1
TTN	ENST00000360870.10	c.2228C>T	p.Ala743Val	missense_variant	14/46	5	NM_133379.5	ENSP00000354117

Frequencies

GnomAD3 genomes AF: 0.0000131 AC: 2 AN: 152122 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.000385

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.00

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 0.00000684 AC: 10 AN: 1461832 Hom.: 0 Cov.: 35 AF XY: 0.0000110 AC XY: 8 AN XY: 727218

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.000252

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.0000131 AC: 2 AN: 152122 Hom.: 0 Cov.: 32 AF XY: 0.0000269 AC XY: 2 AN XY: 74288

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.000385

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

ClinVar

Significance: Uncertain significance

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Dilated cardiomyopathy 1G Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

OMIM

Feb 22, 2002

- -

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

Dec 01, 2023

This sequence change replaces alanine, which is neutral and non-polar, with valine, which is neutral and non-polar, at codon 743 of the TTN protein (p.Ala743Val). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with dilated cardiomyopathy (PMID: 11846417). ClinVar contains an entry for this variant (Variation ID: 12655). Algorithms developed to predict the effect of variants on protein structure and function are not available or were not evaluated for this variant. Experimental studies have shown that this missense change affects TTN function (PMID: 11846417). This variant is located in the Z band of TTN (PMID: 25589632). Non-truncating variants in this region may be clinically relevant, but have not been definitively shown to cause cardiomyopathy or neuromuscular disease (PMID: 27493940, 32778822). 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.094
BayesDel_addAF	Uncertain	0.11	D
BayesDel_noAF	Uncertain	-0.070
CADD	Benign	17
DANN	Benign	0.87
Eigen	Benign	-0.52
Eigen_PC	Benign	-0.45
FATHMM_MKL	Benign	0.57	D
LIST_S2	Benign	0.74	T;T;T;.;T;T;T;T
M_CAP	Benign	0.036	D
MetaRNN	Benign	0.093	T;T;T;T;T;T;T;T
MetaSVM	Benign	-0.86	T
MutationTaster	Benign	1.0	N;N;N;N;N;N;N
PrimateAI	Benign	0.34	T
PROVEAN	Benign	-1.5	N;N;.;.;N;N;.;N
REVEL	Benign	0.27
Sift	Benign	0.042	D;T;.;.;T;T;.;D
Sift4G	Uncertain	0.019	.;.;.;.;.;.;.;D
Polyphen		0.0, 0.0030	.;.;.;B;.;.;B;B
Vest4		0.58
MutPred		0.46		Gain of methylation at K745 (P = 0.0916);.;Gain of methylation at K745 (P = 0.0916);Gain of methylation at K745 (P = 0.0916);.;.;Gain of methylation at K745 (P = 0.0916);Gain of methylation at K745 (P = 0.0916);
MVP		0.28
MPC		0.083
ClinPred		0.19	T
GERP RS		5.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.040		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: rs267607157; hg19: chr2-179650717;