2-178556857-C-T

Variant names:

Variant summary

Our verdict is Benign. The variant received -16 ACMG points: 0P and 16B. BP4_StrongBP6_Very_StrongBS1

The NM_001267550.2(TTN):c.88297G>A(p.Asp29433Asn) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000271 in 1,613,372 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 Likely benign (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. D29433H) has been classified as Uncertain significance.

Frequency

Genomes: 𝑓 0.0014 ( 0 hom., cov: 33)

Exomes 𝑓: 0.00015 ( 0 hom. )

Consequence

TTN
NM_001267550.2 missense

Scores

Clinical Significance

Benign/Likely benign criteria provided, multiple submitters, no conflicts B:13

Conservation

PhyloP100: 7.91

Publications

2 publications found

Variant links:

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 links:

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]

TTN-AS1 links:

ENSG00000279598 (HGNC:):

ENSG00000279598 links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Benign. The variant received -16 ACMG points.

BP4

Computational evidence support a benign effect (MetaRNN=0.008444011).

BP6

Variant 2-178556857-C-T is Benign according to our data. Variant chr2-178556857-C-T is described in ClinVar as Benign/Likely_benign. ClinVar VariationId is 165766.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

BS1

Variant frequency is greater than expected in population afr. GnomAd4 allele frequency = 0.0014 (213/152256) while in subpopulation AFR AF = 0.0046 (191/41550). AF 95% confidence interval is 0.00406. There are 0 homozygotes in GnomAd4. There are 100 alleles in the male GnomAd4 subpopulation. Median coverage is 33. This position passed quality control check.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_001267550.2. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein
TTN	NM_001267550.2	MANE Select	c.88297G>A	p.Asp29433Asn	missense	Exon 330 of 363	NP_001254479.2
TTN	NM_001256850.1		c.83374G>A	p.Asp27792Asn	missense	Exon 280 of 313	NP_001243779.1
TTN	NM_133378.4		c.80593G>A	p.Asp26865Asn	missense	Exon 279 of 312	NP_596869.4

Ensembl Transcripts

Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein
TTN	ENST00000589042.5	TSL:5 MANE Select	c.88297G>A	p.Asp29433Asn	missense	Exon 330 of 363	ENSP00000467141.1
TTN	ENST00000446966.2	TSL:1	c.88141G>A	p.Asp29381Asn	missense	Exon 328 of 361	ENSP00000408004.2
TTN	ENST00000436599.2	TSL:1	c.88021G>A	p.Asp29341Asn	missense	Exon 328 of 361	ENSP00000405517.2

Frequencies

GnomAD3 genomes

AF:

0.00139

AC:

212

AN:

152138

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00459

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.000655

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.0000588

Gnomad OTH

AF:

0.00383

GnomAD2 exomes

AF:

0.000355

AC:

AN:

248128

AF XY:

0.000238

show subpopulations

Gnomad AFR exome

AF:

0.00472

Gnomad AMR exome

AF:

0.000319

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.0000356

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.000153

AC:

224

AN:

1461116

Hom.:

Cov.:

AF XY:

0.000120

AC XY:

AN XY:

726854

show subpopulations

African (AFR)

AF:

0.00478

AC:

160

AN:

33474

American (AMR)

AF:

0.000358

AC:

AN:

44714

Ashkenazi Jewish (ASJ)

AF:

0.0000766

AC:

AN:

26122

East Asian (EAS)

AF:

0.00

AC:

AN:

39626

South Asian (SAS)

AF:

0.0000116

AC:

AN:

86226

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53062

Middle Eastern (MID)

AF:

0.000173

AC:

AN:

5764

European-Non Finnish (NFE)

AF:

0.0000252

AC:

AN:

1111766

Other (OTH)

AF:

0.000265

AC:

AN:

60362

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.475

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

GnomAD4 genome

AF:

0.00140

AC:

213

AN:

152256

Hom.:

Cov.:

AF XY:

0.00134

AC XY:

100

AN XY:

74440

show subpopulations

African (AFR)

AF:

0.00460

AC:

191

AN:

41550

American (AMR)

AF:

0.000654

AC:

AN:

15294

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3472

East Asian (EAS)

AF:

0.00

AC:

AN:

5178

South Asian (SAS)

AF:

0.00

AC:

AN:

4828

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10604

Middle Eastern (MID)

AF:

0.00

AC:

AN:

292

European-Non Finnish (NFE)

AF:

0.0000588

AC:

AN:

68016

Other (OTH)

AF:

0.00379

AC:

AN:

2110

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.510

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Genome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

Alfa

AF:

0.000472

Hom.:

Bravo

AF:

0.00154

ESP6500AA

AF:

0.00369

AC:

ESP6500EA

AF:

0.00

AC:

ExAC

AF:

0.000430

AC:

Asia WGS

AF:

0.000289

AC:

AN:

3476

EpiCase

AF:

0.00

EpiControl

AF:

0.000178

ClinVar

Significance: Benign/Likely benign

Submissions summary: Benign:13

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

not specified

Benign:5

Oct 31, 2015

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Asp26865Asn in exon 279 of TTN: This variant is not expected to have clinical si gnificance because it has been identified in 0.5% (45/9664) of African chromoso mes by the Exome Aggregation Consortium (ExAC, http://exac.broadinstitute.org; d bSNP rs189202799).

Apr 09, 2025

Molecular Diagnostic Laboratory for Inherited Cardiovascular Disease, Montreal Heart Institute

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Oct 10, 2017

GeneDx

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

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.

Aug 19, 2016

Eurofins Ntd Llc (ga)

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Jun 12, 2023

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.80593G>A (p.Asp26865Asn) results in a conservative amino acid change located in the A-band region of the encoded protein sequence. Two of four in-silico tools predict a benign effect of the variant on protein function. The variant allele was found at a frequency of 0.00035 in 248128 control chromosomes, predominantly at a frequency of 0.0047 within the African or African-American subpopulation in the gnomAD database. The observed variant frequency within African or African-American control individuals in the gnomAD database is approximately 12-fold of the estimated maximal expected allele frequency for a pathogenic variant in TTN causing Dilated Cardiomyopathy phenotype (0.00039), strongly suggesting that the variant is a benign polymorphism found primarily in populations of African or African-American origin. To our knowledge, no occurrence of c.80593G>A in individuals affected with Dilated Cardiomyopathy and no experimental evidence demonstrating its impact on protein function have been reported in the literature. Additionally, a co-occurrence with another pathogenic variant has been observed (TTR c.424G>A, p.Val142Ile; internal data), providing supporting evidence for a benign role. Seven clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 and all classified the variant as benign (n=3)/likely benign (n=4). Based on the evidence outlined above, the variant was classified as benign.

TTN-related disorder

Benign:1

Nov 10, 2020

PreventionGenetics, part of Exact Sciences

Significance:Likely benign

Review Status:no assertion criteria provided

Collection Method:clinical testing

This variant is classified as likely benign based on ACMG/AMP sequence variant interpretation guidelines (Richards et al. 2015 PMID: 25741868, with internal and published modifications).

Autosomal recessive limb-girdle muscular dystrophy type 2J

Benign:1

Sep 10, 2021

Genome-Nilou Lab

Significance:Benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

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

Early-onset myopathy with fatal cardiomyopathy

Benign:1

Sep 10, 2021

Genome-Nilou Lab

Significance:Benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

not provided

Benign:1

Jul 20, 2018

Athena Diagnostics

Significance:Benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Tibial muscular dystrophy

Benign:1

Sep 10, 2021

Genome-Nilou Lab

Significance:Benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Myopathy, myofibrillar, 9, with early respiratory failure

Benign:1

Sep 10, 2021

Genome-Nilou Lab

Significance:Benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Cardiovascular phenotype

Benign:1

Jul 09, 2018

Ambry Genetics

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

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 v4.9

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Uncertain

0.38

BayesDel_addAF

Benign

-0.50

BayesDel_noAF

Benign

-0.49

CADD

Benign

(source)

DANN

Benign

0.97

Eigen

Pathogenic

0.73

Eigen_PC

Pathogenic

0.75

FATHMM_MKL

Pathogenic

0.99

LIST_S2

Uncertain

0.94

M_CAP

Benign

0.045

MetaRNN

Benign

0.0084

MetaSVM

Benign

-0.67

MutationAssessor

Pathogenic

3.4

PhyloP100

7.9

PrimateAI

Uncertain

0.70

PROVEAN

Uncertain

-3.5

REVEL

Uncertain

0.35

Sift

Uncertain

0.0030

Polyphen

0.98

Vest4

0.38

MVP

0.25

MPC

0.22

ClinPred

0.072

GERP RS

5.9

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.1

Mutation Taster

=81/19

polymorphism

(source)

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.010

Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Variant Effect in Transcripts

RefSeq Transcripts

Ensembl Transcripts

Frequencies

Age Distribution

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over