chr2-178800524-T-C

Variant names:

• chr2-178800524-T-C
• rs786205406
• NM_001267550.2:c.454A>G

Variant summary

Our verdict is Uncertain significance. Variant got 0 ACMG points: 2P and 2B. PM2 BP4_Moderate

The NM_001267550.2(TTN):​c.454A>G​(p.Ile152Val) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. 12/18 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 6.17

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 Uncertain_significance. Variant got 0 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.2561349).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTN	NM_001267550.2	c.454A>G	p.Ile152Val	missense_variant	Exon 4 of 363	ENST00000589042.5	NP_001254479.2
TTN	NM_133379.5	c.454A>G	p.Ile152Val	missense_variant	Exon 4 of 46	ENST00000360870.10	NP_596870.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.454A>G	p.Ile152Val	missense_variant	Exon 4 of 363	5	NM_001267550.2	ENSP00000467141.1
TTN	ENST00000360870.10	c.454A>G	p.Ile152Val	missense_variant	Exon 4 of 46	5	NM_133379.5	ENSP00000354117.4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Uncertain:1

Jun 24, 2013

Biesecker Lab/Clinical Genomics Section, National Institutes of Health

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: research

- -

Cardiovascular phenotype Uncertain:1

Sep 30, 2015

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.I152V variant (also known as c.454A>G), located in coding exon 3 of the TTN gene, results from an A to G substitution at nucleotide position 454. The isoleucine at codon 152 is replaced by valine, an amino acid with highly similar properties. The p.I152V variant has been reported as a secondary cardiac variant of unknown significance in an exome cohort (Ng D et al. Circ Cardiovasc Genet. 2013;6(4):337-46). This variant was previously reported in the SNPDatabase as rs786205406. This variant was not reported in population based cohorts in the following databases: NHLBI Exome Sequencing Project (ESP) and 1000 Genomes Project. In the ESP, this variant was not observed in 6503 samples (13006 alleles) with coverage at this position. This amino acid position is well conserved in available vertebrate species. In addition, this alteration is predicted to be tolerated by in silico analysis. Since supporting evidence is limited at this time, the clinical significance of this variant remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.32
BayesDel_addAF	Benign	-0.087	T
BayesDel_noAF	Benign	-0.36
CADD	Benign	23
DANN	Benign	0.95
Eigen	Uncertain	0.21
Eigen_PC	Uncertain	0.37
FATHMM_MKL	Uncertain	0.97	D
LIST_S2	Uncertain	0.94	D;D;D;.;D;D;D;D
M_CAP	Benign	0.016	T
MetaRNN	Benign	0.26	T;T;T;T;T;T;T;T
MetaSVM	Benign	-0.71	T
PrimateAI	Uncertain	0.70	T
PROVEAN	Benign	-0.62	N;N;.;.;N;N;.;N
REVEL	Benign	0.14
Sift	Benign	0.22	T;T;.;.;T;T;.;D
Sift4G	Uncertain	0.048	.;.;.;.;.;.;.;D
Polyphen		0.053, 0.75	.;.;.;B;.;.;B;P
Vest4		0.35
MutPred		0.37		Loss of sheet (P = 0.0817);Loss of sheet (P = 0.0817);Loss of sheet (P = 0.0817);Loss of sheet (P = 0.0817);Loss of sheet (P = 0.0817);Loss of sheet (P = 0.0817);Loss of sheet (P = 0.0817);Loss of sheet (P = 0.0817);
MVP		0.49
MPC		0.089
ClinPred		0.34	T
GERP RS		6.0

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: rs786205406; hg19: chr2-179665251;