chr2-178620030-C-T

Position:

• chr2-178620030-C-T

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 1P and 3B. PP2 BP4_Moderate BP6

The NM_001267550.2(TTN):​c.46387G>A​(p.Gly15463Arg) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00044 in 1,611,770 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: 𝑓 0.00028 (0 hom., cov: 32)
  • Exomes 𝑓: 0.00046 (0 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:9 B:4
• Conservation: PhyloP100: 7.80

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 Likely_benign. Variant got -2 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=0.18501413).
• BP6: Variant 2-178620030-C-T is Benign according to our data. Variant chr2-178620030-C-T is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 47000.We mark this variant Likely_benign, oryginal submissions are: {Likely_benign=2, Uncertain_significance=9, Benign=2}. Variant chr2-178620030-C-T is described in Lovd as [Likely_benign].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTN	NM_001267550.2	c.46387G>A	p.Gly15463Arg	missense_variant	249/363	ENST00000589042.5	NP_001254479.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.46387G>A	p.Gly15463Arg	missense_variant	249/363	5	NM_001267550.2	ENSP00000467141.1

Frequencies

GnomAD3 genomes AF: 0.000264 AC: 40 AN: 151754 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.000314

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.000195

Gnomad SAS AF: 0.000415

Gnomad FIN AF: 0.0000943

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.000339

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.000292 AC: 72 AN: 246698 Hom.: 0 AF XY: 0.000269 AC XY: 36 AN XY: 133852

Gnomad AFR exome AF: 0.000324

Gnomad AMR exome AF: 0.0000583

Gnomad ASJ exome AF: 0.000200

Gnomad EAS exome AF: 0.0000564

Gnomad SAS exome AF: 0.0000327

Gnomad FIN exome AF: 0.000140

Gnomad NFE exome AF: 0.000512

Gnomad OTH exome AF: 0.000167

GnomAD4 exome AF: 0.000457 AC: 667 AN: 1459898 Hom.: 0 Cov.: 31 AF XY: 0.000425 AC XY: 309 AN XY: 726212

Gnomad4 AFR exome AF: 0.000150

Gnomad4 AMR exome AF: 0.000112

Gnomad4 ASJ exome AF: 0.000154

Gnomad4 EAS exome AF: 0.000329

Gnomad4 SAS exome AF: 0.0000464

Gnomad4 FIN exome AF: 0.000319

Gnomad4 NFE exome AF: 0.000551

Gnomad4 OTH exome AF: 0.000116

GnomAD4 genome AF: 0.000277 AC: 42 AN: 151872 Hom.: 0 Cov.: 32 AF XY: 0.000269 AC XY: 20 AN XY: 74234

Gnomad4 AFR AF: 0.000362

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.000195

Gnomad4 SAS AF: 0.000415

Gnomad4 FIN AF: 0.0000943

Gnomad4 NFE AF: 0.000339

Gnomad4 OTH AF: 0.00

Alfa AF: 0.000365 Hom.: 0

Bravo AF: 0.000242

TwinsUK AF: 0.000270 AC: 1

ALSPAC AF: 0.000259 AC: 1

ESP6500AA AF: 0.000271 AC: 1

ESP6500EA AF: 0.000365 AC: 3

ExAC AF: 0.000339 AC: 41

Asia WGS AF: 0.000289 AC: 1 AN: 3476

EpiCase AF: 0.000437

EpiControl AF: 0.000356

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:9 Benign:4

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Uncertain:3 Benign:1

Likely benign, criteria provided, single submitter	clinical testing	GeneDx	Mar 02, 2021	This variant is associated with the following publications: (PMID: 26265630, 21810661) -
Uncertain significance, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Nov 01, 2022	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Feb 03, 2017	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Aug 19, 2020	- -

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Mar 27, 2013

The Gly12895Arg variant in TTN has not been reported in the literature, but has been identified by our laboratory in one individual with DCM (LMM unpublished da ta). This variant has been identified in 3/8228 European American chromosomes f rom a broad population by the NHLBI Exome Sequencing Project (http://evs.gs.wash ington.edu/EVS/; dbSNP rs200042932). Computational analyses (biochemical amino a cid properties, conservation, AlignGVGD, PolyPhen2, and SIFT) suggest that the G ly12895Arg variant may impact the protein, though this information is not predic tive enough to determine pathogenicity. In summary, additional information is ne eded to fully assess the clinical significance of the Gly12895Arg variant. -

Autosomal recessive limb-girdle muscular dystrophy type 2J Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

TTN-related disorder Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

PreventionGenetics, part of Exact Sciences

Sep 07, 2022

The TTN c.46387G>A variant is predicted to result in the amino acid substitution p.Gly15463Arg. To our knowledge, this variant has not been reported in the literature. This variant is reported in 0.051% of alleles in individuals of European (Non-Finnish) descent in gnomAD (http://gnomad.broadinstitute.org/variant/2-179484757-C-T). Although we suspect that this variant may be benign, at this time, the clinical significance of this variant is uncertain due to the absence of conclusive functional and genetic evidence. -

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

Nov 28, 2017

- -

Dilated cardiomyopathy 1G Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Early-onset myopathy with fatal cardiomyopathy Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Tibial muscular dystrophy Benign:1

Benign, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score and internal cut-off values, a variant classified as benign is not then subjected to further curation. The score for this variant resulted in a classification of benign for this disease. -

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

Benign, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score and internal cut-off values, a variant classified as benign is not then subjected to further curation. The score for this variant resulted in a classification of benign for this disease. -

Cardiovascular phenotype Benign:1

Likely benign, criteria provided, single submitter

clinical testing

Ambry Genetics

Jul 29, 2019

This alteration is classified as likely benign based on a combination of the following: seen in unaffected individuals, population frequency, intact protein function, lack of segregation with disease, co-occurrence, RNA analysis, in silico models, amino acid conservation, lack of disease association in case-control studies, and/or the mechanism of disease or impacted region is inconsistent with a known cause of pathogenicity. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.74
BayesDel_addAF	Benign	-0.11	T
BayesDel_noAF	Uncertain	-0.060
CADD	Uncertain	24
DANN	Benign	0.96
Eigen	Pathogenic	0.69
Eigen_PC	Pathogenic	0.75
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.95	D;D;D;.;D;D;D
M_CAP	Benign	0.029	D
MetaRNN	Benign	0.19	T;T;T;T;T;T;T
MetaSVM	Benign	-0.40	T
MutationAssessor	Benign	0.72	.;.;.;N;.;.;N
MutationTaster	Benign	1.0	D;D;D;D;D;D
PrimateAI	Uncertain	0.79	T
PROVEAN	Pathogenic	-4.8	D;D;.;.;D;D;.
REVEL	Uncertain	0.46
Sift	Benign	0.11	T;T;.;.;T;T;.
Polyphen		1.0	.;.;.;D;.;.;D
Vest4		0.60
MutPred		0.48		.;.;.;Gain of disorder (P = 0.0444);.;.;Gain of disorder (P = 0.0444);
MVP		0.73
MPC		0.51
ClinPred		0.80	D
GERP RS		5.7

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		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: rs200042932; hg19: chr2-179484757;