2-178693949-G-C

Position:

• chr2-178693949-G-C

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 3P and 2B. PM2 PP2 BP4_Moderate

The NM_001267550.2(TTN):​c.31486C>G​(p.His10496Asp) 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. 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:3
• Conservation: PhyloP100: 4.32

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]

LOC124907912 (HGNC:):

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]

ACMG classification

Verdict is Uncertain_significance. Variant got 1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• 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=0.24420094).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTN	NM_001267550.2	c.31486C>G	p.His10496Asp	missense_variant	118/363	ENST00000589042.5	NP_001254479.2
LOC124907912	XR_007087321.1	n.5812G>C		non_coding_transcript_exon_variant	1/2
LOC124906100	XR_007087318.1	n.2186-19805G>C		intron_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.31486C>G	p.His10496Asp	missense_variant	118/363	5	NM_001267550.2	ENSP00000467141	P1
TTN-AS1	ENST00000659121.1	n.503-40555G>C		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories	Jan 04, 2018	The TTN c.27754C>G; p.His9252Asp variant, to our knowledge, is not reported in the medical literature, gene specific variation databases, nor has it been previously identified by our laboratory. This variant is absent from the general population databases (1000 Genomes Project, Exome Variant Server, Genome Aggregation Database), indicating it is not a common polymorphism. The histidine at position 9252 is moderately conserved, considering 10 species, and computational analyses of the effects of the p.His9252Asp variant on protein structure and function make conflicting predictions (SIFT: tolerated, MutationTaster: disease causing, AlignGVGD: Class C0). Given the available evidence, the clinical significance of the p.His9252Asp variant cannot be determined with certainty. -
Uncertain significance, criteria provided, single submitter	clinical testing	GeneDx	Nov 13, 2023	Not observed at significant frequency in large population cohorts (gnomAD); Missense variant in a gene in which most reported pathogenic variants are truncating/loss of function; Has not been previously published as pathogenic or benign to our knowledge -

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

Oct 30, 2017

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.38
BayesDel_addAF	Benign	-0.044	T
BayesDel_noAF	Benign	-0.30
CADD	Benign	21
DANN	Uncertain	0.99
DEOGEN2	Benign	0.10	.;.;.;.;T
Eigen	Benign	0.0037
Eigen_PC	Benign	0.20
FATHMM_MKL	Uncertain	0.91	D
LIST_S2	Benign	0.49	T;T;.;T;T
M_CAP	Benign	0.028	D
MetaRNN	Benign	0.24	T;T;T;T;T
MetaSVM	Benign	-0.77	T
MutationTaster	Benign	1.0	D;D;D;N;N;N
PrimateAI	Uncertain	0.63	T
PROVEAN	Uncertain	-4.0	D;.;.;.;D
REVEL	Benign	0.18
Sift	Uncertain	0.028	D;.;.;.;D
Polyphen		0.093	.;.;B;B;.
Vest4		0.48
MutPred		0.11		.;.;Gain of phosphorylation at T10180 (P = 0.1213);Gain of phosphorylation at T10180 (P = 0.1213);.;
MVP		0.25
MPC		0.15
ClinPred		0.69	D
GERP RS		5.3

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: rs1553860465; hg19: chr2-179558676;