2-178775871-C-T

Variant names:

• chr2-178775871-C-T
• rs144135510
• NM_001267550.2:c.5993G>A

Variant summary

Our verdict is Benign. The variant received -13 ACMG points: 0P and 13B. BP4_Strong BP6 BS1 BS2

The NM_001267550.2(TTN):​c.5993G>A​(p.Arg1998His) variant causes a missense change. The variant allele was found at a frequency of 0.000918 in 1,614,130 control chromosomes in the GnomAD database, including 15 homozygotes. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R1998L) has been classified as Uncertain significance.

• Frequency:
  • Genomes: 𝑓 0.00081 (1 hom., cov: 33)
  • Exomes 𝑓: 0.00093 (14 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:3 B:18 O:1
• Conservation: PhyloP100: 4.80
• Publications: 12 publications found

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

Our verdict: Benign. The variant received -13 ACMG points.

• BP4: Computational evidence support a benign effect (MetaRNN=0.0073085725).
• BP6: Variant 2-178775871-C-T is Benign according to our data. Variant chr2-178775871-C-T is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 47256.
• BS1: Variant frequency is greater than expected in population sas. GnomAd4 allele frequency = 0.000808 (123/152296) while in subpopulation SAS AF = 0.00871 (42/4824). AF 95% confidence interval is 0.00662. There are 1 homozygotes in GnomAd4. There are 67 alleles in the male GnomAd4 subpopulation. Median coverage is 33. This position passed quality control check.
• BS2: High Homozygotes in GnomAdExome4 at 14 AD,AR gene

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTN	NM_001267550.2	c.5993G>A	p.Arg1998His	missense_variant	Exon 28 of 363	ENST00000589042.5	NP_001254479.2
TTN	NM_133379.5	c.5993G>A	p.Arg1998His	missense_variant	Exon 28 of 46	ENST00000360870.10	NP_596870.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.5993G>A	p.Arg1998His	missense_variant	Exon 28 of 363	5	NM_001267550.2	ENSP00000467141.1
TTN	ENST00000360870.10	c.5993G>A	p.Arg1998His	missense_variant	Exon 28 of 46	5	NM_133379.5	ENSP00000354117.4

Frequencies

GnomAD3 genomes AF: 0.000808 AC: 123 AN: 152178 Hom.: 1 Cov.: 33

Gnomad AFR AF: 0.000121

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000196

Gnomad ASJ AF: 0.00663

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00870

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.000735

Gnomad OTH AF: 0.00

GnomAD2 exomes AF: 0.00162 AC: 406 AN: 250982 AF XY: 0.00197

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.000145

Gnomad ASJ exome AF: 0.00834

Gnomad EAS exome AF: 0.0000544

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.000670

Gnomad OTH exome AF: 0.00147

GnomAD4 exome AF: 0.000930 AC: 1359 AN: 1461834 Hom.: 14 Cov.: 33 AF XY: 0.00118 AC XY: 857 AN XY: 727220

African (AFR) AF: 0.000179 AC: 6 AN: 33472

American (AMR) AF: 0.000157 AC: 7 AN: 44720

Ashkenazi Jewish (ASJ) AF: 0.00777 AC: 203 AN: 26134

East Asian (EAS) AF: 0.0000252 AC: 1 AN: 39696

South Asian (SAS) AF: 0.00768 AC: 662 AN: 86254

European-Finnish (FIN) AF: 0.0000187 AC: 1 AN: 53414

Middle Eastern (MID) AF: 0.00121 AC: 7 AN: 5768

European-Non Finnish (NFE) AF: 0.000362 AC: 403 AN: 1111982

Other (OTH) AF: 0.00114 AC: 69 AN: 60394

GnomAD4 genome AF: 0.000808 AC: 123 AN: 152296 Hom.: 1 Cov.: 33 AF XY: 0.000900 AC XY: 67 AN XY: 74482

African (AFR) AF: 0.000120 AC: 5 AN: 41576

American (AMR) AF: 0.000196 AC: 3 AN: 15300

Ashkenazi Jewish (ASJ) AF: 0.00663 AC: 23 AN: 3470

East Asian (EAS) AF: 0.00 AC: 0 AN: 5180

South Asian (SAS) AF: 0.00871 AC: 42 AN: 4824

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10618

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 294

European-Non Finnish (NFE) AF: 0.000735 AC: 50 AN: 68008

Other (OTH) AF: 0.00 AC: 0 AN: 2114

Alfa AF: 0.000834 Hom.: 3

Bravo AF: 0.000495

ESP6500AA AF: 0.00 AC: 0

ESP6500EA AF: 0.00116 AC: 10

ExAC AF: 0.00175 AC: 213

Asia WGS AF: 0.00231 AC: 8 AN: 3478

EpiCase AF: 0.000709

EpiControl AF: 0.00107

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:3 Benign:18 Other:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not specified Benign:7

Oct 07, 2019

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: TTN c.5993G>A (p.Arg1998His) results in a non-conservative amino acid change located in the near Z-disk / I-band region of the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 0.0016 in 250982 control chromosomes, predominantly at a frequency of 0.0075 within the South Asian subpopulation in the gnomAD database, including 3 homozygotes. The observed variant frequency within South Asian control individuals in the gnomAD database is approximately 12 fold of the estimated maximal expected allele frequency for a pathogenic variant in TTN causing Cardiomyopathy phenotype (0.00063), strongly suggesting that the variant is a benign polymorphism found primarily in populations of South Asian origin. To our knowledge, no occurrence of c.5993G>A in individuals affected with Cardiomyopathy and no experimental evidence demonstrating its impact on protein function have been reported. Four ClinVar submissions (evaluation after 2014) cite the variant as benign. Based on the evidence outlined above, the variant was classified as benign. -

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Clinical Genetics, Academic Medical Center

Significance: Benign

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Sep 03, 2015

Eurofins Ntd Llc (ga)

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Apr 09, 2025

Molecular Diagnostic Laboratory for Inherited Cardiovascular Disease, Montreal Heart Institute

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Aug 22, 2016

Athena Diagnostics

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

-

Joint Genome Diagnostic Labs from Nijmegen and Maastricht, Radboudumc and MUMC+

Significance: Benign

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Dec 18, 2017

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

proposed classification - variant undergoing re-assessment, contact laboratory -

not provided Benign:5 Other:1

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Clinical Genetics DNA and cytogenetics Diagnostics Lab, Erasmus MC, Erasmus Medical Center

Significance: Likely benign

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

-

Genome Diagnostics Laboratory, University Medical Center Utrecht

Significance: Likely benign

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Mar 01, 2025

CeGaT Center for Human Genetics Tuebingen

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

TTN: BS2 -

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Diagnostic Laboratory, Department of Genetics, University Medical Center Groningen

Significance: Likely benign

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Jun 24, 2013

Biesecker Lab/Clinical Genomics Section, National Institutes of Health

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: research

- -

Mar 14, 2013

GeneDx

Significance: not provided

Review Status: no classification provided

Collection Method: clinical testing

- -

Tip-toe gait Pathogenic:1

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Practice for Gait Abnormalities, David Pomarino, Competency Network Toe Walking c/o Practice Pomarino

Significance: Likely pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

Myopathy refers to diseases that affect skeletal Muscles. These diseases attack muscle fibers, making muscles weak. Inherited myopathies are often caused by inheriting an abnormal gene mutation from a parent that causes the disease. Symptoms of congenital myopathies usually start at birth or in early childhood, but may not appear until the teen years or even later in adulthood. Congenital myopathies are somewhat unique compared with other inherited myopathies, as weakness typically affects all muscles and is often not progressive. Symptoms are: Muscle weakness, most commonly of upper arms and shoulders and thighs, muscle cramps, stiffness and spasms, fatigue with exertion and lack of energy. Our patients all walk on tiptoe, so they show similar symptoms. When we genetically test them with our toe walking panel, we find that around 90 per cent of them have a genetic variant that explains their toe walking. These can be assigned, for example, to the area of myopathies (such as variants of the COL6A3 gene), the area of hereditary neuropathies (such as variants of the KMT2C gene) or the area of metabolic diseases (such as variants of the PYGM gene). In a smaller group of patients with almost identical symptoms, no abnormality is found in the genes of our panel, but spastic paraplegia can be detected. In another small group of our toe walkers, no abnormalities can be detected in the genes analysed in our toe walking panel, nor do they suffer from spastic paraplegia, as is also the case with healthy children. In contrast to these, however, they show a tiptoe gait. These patients suffer from infantile cerebral palsy, in which toe walking can also be observed. -

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

Apr 27, 2017

Illumina Laboratory Services, Illumina

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed as part of a predisposition screen in an ostensibly healthy population. A literature search was performed for the gene, cDNA change, and amino acid change (where applicable). Publications were found based on this search. However, the evidence from the literature, in combination with allele frequency data from public databases where available, was not sufficient to rule this variant in or out of causing disease. Therefore, this variant is classified as a variant of unknown significance. -

Early-onset myopathy with fatal cardiomyopathy Uncertain:1

Apr 27, 2017

Illumina Laboratory Services, Illumina

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed as part of a predisposition screen in an ostensibly healthy population. A literature search was performed for the gene, cDNA change, and amino acid change (where applicable). Publications were found based on this search. However, the evidence from the literature, in combination with allele frequency data from public databases where available, was not sufficient to rule this variant in or out of causing disease. Therefore, this variant is classified as a variant of unknown significance. -

Cardiovascular phenotype Uncertain:1

Jan 06, 2013

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

There is insufficient or conflicting evidence for classification of this alteration. -

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

Feb 02, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Dilated cardiomyopathy 1G Benign:1

Apr 27, 2017

Illumina Laboratory Services, Illumina

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed as part of a predisposition screen in an ostensibly healthy population. A literature search was performed for the gene, cDNA change, and amino acid change (where applicable). Publications were found based on this search. The evidence from the literature, in combination with allele frequency data from public databases where available, was sufficient to determine this variant is unlikely to cause disease. Therefore, this variant is classified as likely benign. -

Cardiomyopathy Benign:1

Oct 19, 2021

CHEO Genetics Diagnostic Laboratory, Children's Hospital of Eastern Ontario

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

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

Apr 27, 2017

Illumina Laboratory Services, Illumina

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed as part of a predisposition screen in an ostensibly healthy population. A literature search was performed for the gene, cDNA change, and amino acid change (where applicable). Publications were found based on this search. The evidence from the literature, in combination with allele frequency data from public databases where available, was sufficient to rule this variant out of causing disease. Therefore, this variant is classified as benign. -

Tibial muscular dystrophy Benign:1

Apr 27, 2017

Illumina Laboratory Services, Illumina

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed as part of a predisposition screen in an ostensibly healthy population. A literature search was performed for the gene, cDNA change, and amino acid change (where applicable). Publications were found based on this search. The evidence from the literature, in combination with allele frequency data from public databases where available, was sufficient to rule this variant out of causing disease. Therefore, this variant is classified as benign. -

TTN-related myopathy Benign:1

Jun 06, 2023

Molecular Genetics, Royal Melbourne Hospital

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.23
BayesDel_addAF	Benign	-0.30	T
BayesDel_noAF	Benign	-0.20
CADD	Pathogenic	27
DANN	Uncertain	0.97
Eigen	Uncertain	0.57
Eigen_PC	Uncertain	0.59
FATHMM_MKL	Uncertain	0.91	D
LIST_S2	Pathogenic	0.98	D;D;D;.;D;D;D;D
M_CAP	Benign	0.048	D
MetaRNN	Benign	0.0073	T;T;T;T;T;T;T;T
MetaSVM	Benign	-0.39	T
PhyloP100		4.8
PrimateAI	Uncertain	0.71	T
PROVEAN	Uncertain	-3.1	D;D;.;.;D;D;.;D
REVEL	Benign	0.25
Sift	Uncertain	0.017	D;D;.;.;D;D;.;D
Sift4G	Pathogenic	0.0010	.;.;.;.;.;.;.;D
Polyphen		1.0	.;.;.;D;.;.;D;D
Vest4		0.34
MVP		0.32
MPC		0.44
ClinPred		0.079	T
GERP RS		5.1
Mutation Taster		=96/4	polymorphism

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

Other links and lift over

dbSNP: rs144135510; hg19: chr2-179640598; COSMIC: COSV60043814; COSMIC: COSV60043814;