2-178785974-C-T

Position:

• chr2-178785974-C-T

Variant summary

Our verdict is Benign. Variant got -19 ACMG points: 0P and 19B. BP4_Moderate BP6_Very_Strong BP7 BA1

The NM_001267550.2(TTN):​c.2244G>A​(p.Glu748=) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.369 in 1,613,814 control chromosomes in the GnomAD database, including 116,401 homozygotes. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Benign (★★).

• Frequency:
  • Genomes: 𝑓 0.32 (8777 hom., cov: 31)
  • Exomes 𝑓: 0.37 (107624 hom.)
• Consequence: TTN NM_001267550.2 synonymous
• Clinical Significance: Benign criteria provided, multiple submitters, no conflicts B:21
• Conservation: PhyloP100: 2.15

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 Benign. Variant got -19 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.35).
• BP6: Variant 2-178785974-C-T is Benign according to our data. Variant chr2-178785974-C-T is described in ClinVar as [Benign]. Clinvar id is 46774.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr2-178785974-C-T is described in Lovd as [Benign]. Variant chr2-178785974-C-T is described in Lovd as [Likely_benign].
• BP7: Synonymous conserved (PhyloP=2.15 with no splicing effect.
• BA1: GnomAd4 highest subpopulation (NFE) allele frequency at 95% confidence interval = 0.405 is higher than 0.05.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTN	NM_001267550.2	c.2244G>A	p.Glu748=	synonymous_variant	14/363	ENST00000589042.5
TTN	NM_133379.5	c.2244G>A	p.Glu748=	synonymous_variant	14/46	ENST00000360870.10

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTN	ENST00000589042.5	c.2244G>A	p.Glu748=	synonymous_variant	14/363	5	NM_001267550.2	P1
TTN	ENST00000360870.10	c.2244G>A	p.Glu748=	synonymous_variant	14/46	5	NM_133379.5

Frequencies

GnomAD3 genomes AF: 0.320 AC: 48659 AN: 151868 Hom.: 8780 Cov.: 31

Gnomad AFR AF: 0.194

Gnomad AMI AF: 0.563

Gnomad AMR AF: 0.245

Gnomad ASJ AF: 0.336

Gnomad EAS AF: 0.0816

Gnomad SAS AF: 0.251

Gnomad FIN AF: 0.475

Gnomad MID AF: 0.414

Gnomad NFE AF: 0.409

Gnomad OTH AF: 0.317

GnomAD3 exomes AF: 0.316 AC: 79397 AN: 251086 Hom.: 14492 AF XY: 0.323 AC XY: 43764 AN XY: 135682

Gnomad AFR exome AF: 0.192

Gnomad AMR exome AF: 0.170

Gnomad ASJ exome AF: 0.329

Gnomad EAS exome AF: 0.0729

Gnomad SAS exome AF: 0.254

Gnomad FIN exome AF: 0.470

Gnomad NFE exome AF: 0.403

Gnomad OTH exome AF: 0.334

GnomAD4 exome AF: 0.374 AC: 547035 AN: 1461828 Hom.: 107624 Cov.: 70 AF XY: 0.372 AC XY: 270315 AN XY: 727220

Gnomad4 AFR exome AF: 0.189

Gnomad4 AMR exome AF: 0.178

Gnomad4 ASJ exome AF: 0.328

Gnomad4 EAS exome AF: 0.0662

Gnomad4 SAS exome AF: 0.256

Gnomad4 FIN exome AF: 0.462

Gnomad4 NFE exome AF: 0.406

Gnomad4 OTH exome AF: 0.346

GnomAD4 genome AF: 0.320 AC: 48653 AN: 151986 Hom.: 8777 Cov.: 31 AF XY: 0.317 AC XY: 23520 AN XY: 74276

Gnomad4 AFR AF: 0.193

Gnomad4 AMR AF: 0.244

Gnomad4 ASJ AF: 0.336

Gnomad4 EAS AF: 0.0816

Gnomad4 SAS AF: 0.251

Gnomad4 FIN AF: 0.475

Gnomad4 NFE AF: 0.409

Gnomad4 OTH AF: 0.315

Alfa AF: 0.377 Hom.: 14985

Bravo AF: 0.294

Asia WGS AF: 0.152 AC: 530 AN: 3478

EpiCase AF: 0.396

EpiControl AF: 0.392

ClinVar

Significance: Benign

Submissions summary: Benign:21

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not specified Benign:8

Benign, no assertion criteria provided	clinical testing	Clinical Genetics DNA and cytogenetics Diagnostics Lab, Erasmus MC, Erasmus Medical Center	-	- -
Benign, no assertion criteria provided	clinical testing	Diagnostic Laboratory, Department of Genetics, University Medical Center Groningen	-	- -
Benign, criteria provided, single submitter	clinical testing	Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine	Sep 16, 2011	- -
Benign, criteria provided, single submitter	clinical testing	GeneDx	Oct 30, 2012	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, criteria provided, single submitter	clinical testing	Genetic Services Laboratory, University of Chicago	Aug 15, 2013	- -
Benign, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Aug 09, 2019	- -
Benign, criteria provided, single submitter	clinical testing	PreventionGenetics, part of Exact Sciences	-	- -
Benign, no assertion criteria provided	clinical testing	Clinical Genetics, Academic 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 12, 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 12, 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. -

not provided Benign:2

Benign, criteria provided, single submitter	clinical testing	Athena Diagnostics	Nov 02, 2018	- -
Benign, criteria provided, single submitter	not provided	Breakthrough Genomics, Breakthrough Genomics	-	- -

Tibial muscular dystrophy Benign:2

Benign, criteria provided, single submitter	clinical testing	Illumina Laboratory Services, Illumina	Jan 12, 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	Genome-Nilou Lab	Sep 10, 2021	- -
Benign, criteria provided, single submitter	clinical testing	Illumina Laboratory Services, Illumina	Jan 12, 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. -

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

Benign, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Feb 01, 2024

- -

Dilated cardiomyopathy 1G Benign:1

Benign, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 12, 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

Benign, criteria provided, single submitter

clinical testing

Ambry Genetics

Feb 07, 2019

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
BayesDel_noAF	Benign	-0.35
CADD	Benign	13
DANN	Benign	0.42

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.060		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: rs6715406; hg19: chr2-179650701; COSMIC: COSV59948304; COSMIC: COSV59948304;