rs56018860

chr2-178568494-T-C

Variant summary

Our verdict is Benign. Variant got -19 ACMG points: 1P and 20B. PP2 BP4_Strong BP6_Very_Strong BA1

The NM_001267550.2(TTN):c.77638A>G(p.Thr25880Ala) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0229 in 1,613,398 control chromosomes in the GnomAD database, including 526 homozygotes. In-silico tool predicts a benign outcome for this variant. 14/18 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Likely benign (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. T25880I) has been classified as Uncertain significance.

• Frequency:
  • Genomes: 𝑓 0.020 (51 hom., cov: 33)
  • Exomes 𝑓: 0.023 (475 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Benign/Likely benign criteria provided, multiple submitters, no conflicts B:23
• Conservation: PhyloP100: 0.742

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: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 Benign. Variant got -19 ACMG points.

• PP2: Missense variant where missense usually causes diseases, TTN
• BP4: Computational evidence support a benign effect (MetaRNN=0.001907289).
• BP6: Variant 2-178568494-T-C is Benign according to our data. Variant chr2-178568494-T-C is described in ClinVar as [Likely_benign]. Clinvar id is 47359.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr2-178568494-T-C is described in Lovd as [Benign]. Variant chr2-178568494-T-C is described in Lovd as [Likely_benign].
• BA1: GnomAd4 highest subpopulation (EAS) allele frequency at 95% confidence interval = 0.0561 is higher than 0.05.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTN	NM_001267550.2	c.77638A>G	p.Thr25880Ala	missense_variant	326/363	ENST00000589042.5
TTN-AS1	NR_038272.1	n.2044-14078T>C		intron_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTN	ENST00000589042.5	c.77638A>G	p.Thr25880Ala	missense_variant	326/363	5	NM_001267550.2	P1
TTN-AS1	ENST00000659121.1	n.417-29102T>C		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes AF: 0.0202 AC: 3076 AN: 152058 Hom.: 51 Cov.: 33

Gnomad AFR AF: 0.00449

Gnomad AMI AF: 0.0307

Gnomad AMR AF: 0.0217

Gnomad ASJ AF: 0.0190

Gnomad EAS AF: 0.0616

Gnomad SAS AF: 0.00829

Gnomad FIN AF: 0.0447

Gnomad MID AF: 0.00633

Gnomad NFE AF: 0.0234

Gnomad OTH AF: 0.0196

GnomAD3 exomes AF: 0.0260 AC: 6458 AN: 248186 Hom.: 117 AF XY: 0.0246 AC XY: 3315 AN XY: 134616

Gnomad AFR exome AF: 0.00491

Gnomad AMR exome AF: 0.0338

Gnomad ASJ exome AF: 0.0141

Gnomad EAS exome AF: 0.0617

Gnomad SAS exome AF: 0.00605

Gnomad FIN exome AF: 0.0472

Gnomad NFE exome AF: 0.0233

Gnomad OTH exome AF: 0.0259

GnomAD4 exome AF: 0.0232 AC: 33842 AN: 1461222 Hom.: 475 Cov.: 41 AF XY: 0.0228 AC XY: 16561 AN XY: 726894

Gnomad4 AFR exome AF: 0.00404

Gnomad4 AMR exome AF: 0.0320

Gnomad4 ASJ exome AF: 0.0143

Gnomad4 EAS exome AF: 0.0634

Gnomad4 SAS exome AF: 0.00669

Gnomad4 FIN exome AF: 0.0483

Gnomad4 NFE exome AF: 0.0224

Gnomad4 OTH exome AF: 0.0218

GnomAD4 genome AF: 0.0202 AC: 3073 AN: 152176 Hom.: 51 Cov.: 33 AF XY: 0.0207 AC XY: 1537 AN XY: 74382

Gnomad4 AFR AF: 0.00448

Gnomad4 AMR AF: 0.0216

Gnomad4 ASJ AF: 0.0190

Gnomad4 EAS AF: 0.0617

Gnomad4 SAS AF: 0.00767

Gnomad4 FIN AF: 0.0447

Gnomad4 NFE AF: 0.0234

Gnomad4 OTH AF: 0.0194

Alfa AF: 0.0229 Hom.: 87

Bravo AF: 0.0185

TwinsUK AF: 0.0262 AC: 97

ALSPAC AF: 0.0244 AC: 94

ESP6500AA AF: 0.00569 AC: 22

ESP6500EA AF: 0.0209 AC: 173

ExAC AF: 0.0261 AC: 3153

Asia WGS AF: 0.0280 AC: 96 AN: 3476

EpiCase AF: 0.0202

EpiControl AF: 0.0218

ClinVar

Significance: Benign/Likely benign

Submissions summary: Benign:23

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not specified Benign:11

Benign, criteria provided, single submitter	clinical testing	Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine	Apr 24, 2012	- -
Benign, criteria provided, single submitter	research	Biesecker Lab/Clinical Genomics Section, National Institutes of Health	Jun 24, 2013	- -
Benign, no assertion criteria provided	clinical testing	Genome Diagnostics Laboratory, University Medical Center Utrecht	-	- -
Benign, no assertion criteria provided	clinical testing	Joint Genome Diagnostic Labs from Nijmegen and Maastricht, Radboudumc and MUMC+	-	- -
Benign, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Jul 23, 2013	- -
Benign, criteria provided, single submitter	clinical testing	PreventionGenetics, part of Exact Sciences	-	- -
Likely benign, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Jan 11, 2020	- -
Benign, criteria provided, single submitter	clinical testing	Genetic Services Laboratory, University of Chicago	Aug 15, 2013	- -
Benign, criteria provided, single submitter	clinical testing	GeneDx	Apr 29, 2013	This variant is considered likely benign or benign based on one or more of the following criteria: it is a conservative change, it occurs at a poorly conserved position in the protein, it is predicted to be benign by multiple in silico algorithms, and/or has population frequency not consistent with disease. -
Benign, no assertion criteria provided	clinical testing	Clinical Genetics, Academic Medical Center	-	- -
Benign, no assertion criteria provided	clinical testing	Clinical Genetics DNA and cytogenetics Diagnostics Lab, Erasmus MC, Erasmus Medical Center	-	- -

Autosomal recessive limb-girdle muscular dystrophy type 2J Benign:2

Benign, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Sep 10, 2021	- -
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. -

Early-onset myopathy with fatal cardiomyopathy Benign:2

Benign, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Sep 10, 2021	- -
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. -

Tibial muscular dystrophy Benign:2

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. -
Benign, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Sep 10, 2021	- -

Myopathy, myofibrillar, 9, with early respiratory failure Benign:2

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. -
Benign, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Sep 10, 2021	- -

Autosomal recessive limb-girdle muscular dystrophy type 2J;C1858763:Dilated cardiomyopathy 1G Benign:1

Benign, criteria provided, single submitter

clinical testing

Invitae

Feb 01, 2024

- -

Dilated cardiomyopathy 1G Benign:1

Likely 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 likely benign is not then subjected to further curation. The score for this variant resulted in a classification of likely benign for this disease. -

not provided Benign:1

Benign, criteria provided, single submitter

clinical testing

Athena Diagnostics

Jan 16, 2019

- -

Cardiovascular phenotype Benign:1

Benign, criteria provided, single submitter

clinical testing

Ambry Genetics

Mar 06, 2013

This alteration is classified as benign based on a combination of the following: 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	Benign	0.074
BayesDel_addAF	Benign	-0.52	T
BayesDel_noAF	Benign	-0.47
Cadd	Benign	14
Dann	Benign	0.79
Eigen	Benign	-0.51
Eigen_PC	Benign	-0.42
FATHMM_MKL	Benign	0.64	D
LIST_S2	Benign	0.72	T;T;T;.;T;T;T
MetaRNN	Benign	0.0019	T;T;T;T;T;T;T
MetaSVM	Benign	-0.95	T
MutationTaster	Benign	0.99	N;N;N;N;N;N
PrimateAI	Benign	0.29	T
PROVEAN	Benign	-2.3	N;N;.;.;N;N;.
REVEL	Benign	0.12
Sift	Benign	0.30	T;T;.;.;T;T;.
Polyphen		0.0	.;.;.;B;.;.;B
Vest4		0.14
MPC		0.082
ClinPred		0.0049	T
GERP RS		-1.1

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: rs56018860; hg19: chr2-179433221; COSMIC: COSV60085185;