2-178554093-C-T

Variant names:

Variant summary

Our verdict is Likely benign. The variant received -3 ACMG points: 0P and 3B. BP4_ModerateBP6

The NM_001267550.2(TTN):c.89018G>A(p.Arg29673Gln) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000143 in 1,613,742 control chromosomes in the GnomAD database, including 1 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. R29673L) has been classified as Uncertain significance.

Frequency

Genomes: 𝑓 0.00021 ( 0 hom., cov: 33)

Exomes 𝑓: 0.00014 ( 1 hom. )

Consequence

TTN
NM_001267550.2 missense

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:11B:4

Conservation

PhyloP100: 7.76

Publications

6 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:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Likely_benign. The variant received -3 ACMG points.

BP4

Computational evidence support a benign effect (MetaRNN=0.1433894).

BP6

Variant 2-178554093-C-T is Benign according to our data. Variant chr2-178554093-C-T is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 165761.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTN	NM_001267550.2 link	c.89018G>A	p.Arg29673Gln	missense_variant	Exon 333 of 363	ENST00000589042.5	NP_001254479.2	A0A0A0MTS7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5 link	c.89018G>A	p.Arg29673Gln	missense_variant	Exon 333 of 363	5	NM_001267550.2	ENSP00000467141.1		A0A0A0MTS7

Frequencies

GnomAD3 genomes

AF:

0.000210

AC:

AN:

152158

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00157

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:

0.000103

Gnomad OTH

AF:

0.000479

GnomAD2 exomes

AF:

0.000229

AC:

AN:

248486

AF XY:

0.000275

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.000811

Gnomad ASJ exome

AF:

0.0000996

Gnomad EAS exome

AF:

0.0000556

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.000169

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.000136

AC:

199

AN:

1461584

Hom.:

Cov.:

AF XY:

0.000151

AC XY:

110

AN XY:

727076

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

33470

American (AMR)

AF:

0.000716

AC:

AN:

44722

Ashkenazi Jewish (ASJ)

AF:

0.0000383

AC:

AN:

26130

East Asian (EAS)

AF:

0.0000504

AC:

AN:

39696

South Asian (SAS)

AF:

0.000220

AC:

AN:

86252

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53390

Middle Eastern (MID)

AF:

0.000694

AC:

AN:

5766

European-Non Finnish (NFE)

AF:

0.000114

AC:

127

AN:

1111788

Other (OTH)

AF:

0.000232

AC:

AN:

60370

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.454

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Exome Hom

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:

0.000210

AC:

AN:

152158

Hom.:

Cov.:

AF XY:

0.000283

AC XY:

AN XY:

74320

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

41442

American (AMR)

AF:

0.00157

AC:

AN:

15274

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3468

East Asian (EAS)

AF:

0.00

AC:

AN:

5184

South Asian (SAS)

AF:

0.00

AC:

AN:

4832

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10616

Middle Eastern (MID)

AF:

0.00

AC:

AN:

316

European-Non Finnish (NFE)

AF:

0.000103

AC:

AN:

68026

Other (OTH)

AF:

0.000479

AC:

AN:

2088

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.497

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:

0.0000508

Hom.:

Bravo

AF:

0.000336

ESP6500AA

AF:

0.00

AC:

ESP6500EA

AF:

0.000363

AC:

ExAC

AF:

0.000199

AC:

EpiCase

AF:

0.000273

EpiControl

AF:

0.000237

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:11Benign:4

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

not provided

Uncertain:8Benign:1

May 09, 2024

Mayo Clinic Laboratories, Mayo Clinic

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

Dec 07, 2023

Revvity Omics, Revvity

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

Jun 24, 2013

Biesecker Lab/Clinical Genomics Section, National Institutes of Health

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:research

- -

Feb 13, 2018

Eurofins Ntd Llc (ga)

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

Laboratory of Diagnostic Genome Analysis, Leiden University Medical Center (LUMC)

Significance:Uncertain significance

Review Status:no assertion criteria provided

Collection Method:clinical testing

- -

Jun 24, 2019

GeneDx

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

Clinical Genetics, Academic Medical Center

Significance:Uncertain significance

Review Status:no assertion criteria provided

Collection Method:clinical testing

- -

Department of Pathology and Laboratory Medicine, Sinai Health System

Significance:Uncertain significance

Review Status:no assertion criteria provided

Collection Method:clinical testing

The TTN p.Arg27105Gln variant was not identified in the literature but was identified in dbSNP (ID: rs200639218) and ClinVar (classified as uncertain signifcance by Invitae, Laboratory for Molecular Medicine, Fulgent Genetics, EGL Genetics and Biesecker Lab/Clinical Genomics Section, National Institutes of Health). The variant was identified in control databases in 60 of 279880 chromosomes at a frequency of 0.0002144 (Genome Aggregation Database March 6, 2019, v2.1.1). The variant was observed in the following populations: Latino in 29 of 35362 chromosomes (freq: 0.00082), Other in 2 of 7114 chromosomes (freq: 0.000281), South Asian in 8 of 30600 chromosomes (freq: 0.000261), European (non-Finnish) in 19 of 127734 chromosomes (freq: 0.000149), Ashkenazi Jewish in 1 of 10334 chromosomes (freq: 0.000097) and East Asian in 1 of 19526 chromosomes (freq: 0.000051), but was not observed in the African or European (Finnish) populations. The p.Arg27105 residue is conserved in mammals and computational analyses (PolyPhen-2, SIFT, AlignGVGD, BLOSUM, MutationTaster) provide inconsistent predictions regarding the impact to the protein; this information is not very predictive of pathogenicity. The variant occurs outside of the splicing consensus sequence and in silico or computational prediction software programs (SpliceSiteFinder, MaxEntScan, NNSPLICE, GeneSplicer) do not predict a difference in splicing. In summary, based on the above information the clinical significance of this variant cannot be determined with certainty at this time. This variant is classified as a variant of uncertain significance. -

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

Significance:Uncertain significance

Review Status:no assertion criteria provided

Collection Method:clinical testing

- -

not specified

Uncertain:1Benign:2

Dec 04, 2024

Athena Diagnostics

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

Feb 17, 2025

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

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Variant summary: TTN c.81314G>A (p.Arg27105Gln) results in a conservative amino acid change in 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 0.00023 in 248486 control chromosomes, predominantly at a frequency of 0.00081 within the Latino subpopulation in the gnomAD database. The observed variant frequency within Latino control individuals in the gnomAD database is approximately 2 fold of the estimated maximal expected allele frequency for a pathogenic variant in TTN causing Autosomal Recessive Titinopathy phenotype (0.00039). c.81314G>A has been reported in the literature in at-least one heterozygous individual who had a sudden unexplained death and in at-least one individual with coronary heart disease (CHD), dilated cardiomyopathy (DCM), or idiopathic ventricular tachycardia (iVT), without strong evidence of causality (example: Campuzano_2015, Guelly_2021). These reports do not provide unequivocal conclusions about association of the variant with Autosomal Recessive Titinopathy or other TTN-related disorders. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. The following publications have been ascertained in the context of this evaluation (PMID: 26516846, 33552729). ClinVar contains an entry for this variant (Variation ID: 165761). Based on the evidence outlined above, the variant was classified as likely benign. -

Dec 04, 2014

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

The p.Arg27105Gln variant in TTN has not been previously reported in individuals with cardiomyopathy, but has been identified in 3/8262 European American chromo somes by the NHLBI Exome Sequencing Project (http://evs.gs.washington.edu/EVS/; dbSNP rs200639218). Computational prediction tools and conservation analysis sug gest that this variant may impact the protein, though this information is not pr edictive enough to determine pathogenicity. In summary, the clinical significanc e of the p.Arg27105Gln variant is uncertain. -

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

Uncertain:1

Jul 25, 2017

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

Autosomal recessive limb-girdle muscular dystrophy type 2J;C1838244:Tibial muscular dystrophy;C1858763:Dilated cardiomyopathy 1G;C1861065:Hypertrophic cardiomyopathy 9;C1863599:Myopathy, myofibrillar, 9, with early respiratory failure;C2673677:Early-onset myopathy with fatal cardiomyopathy

Uncertain:1

Oct 31, 2018

Fulgent Genetics, Fulgent Genetics

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

Cardiomyopathy

Benign:1

Feb 16, 2022

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

Significance:Benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Uncertain

0.38

BayesDel_addAF

Benign

-0.26

BayesDel_noAF

Benign

-0.23

CADD

Benign

(source)

DANN

Uncertain

0.99

Eigen

Pathogenic

0.91

Eigen_PC

Pathogenic

0.88

FATHMM_MKL

Pathogenic

0.99

LIST_S2

Uncertain

0.97

D;D;D;.;D;D;D

M_CAP

Benign

0.016

MetaRNN

Benign

0.14

T;T;T;T;T;T;T

MetaSVM

Uncertain

-0.23

MutationAssessor

Uncertain

2.5

.;.;.;M;.;.;M

PhyloP100

7.8

PrimateAI

Uncertain

0.65

PROVEAN

Uncertain

-2.8

D;D;.;.;D;D;.

REVEL

Uncertain

0.38

Sift

Uncertain

0.010

D;D;.;.;D;D;.

Polyphen

1.0

.;.;.;D;.;.;D

Vest4

0.45

MVP

0.35

MPC

0.50

ClinPred

0.24

GERP RS

5.6

Mutation Taster

=99/1

polymorphism

(source)

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

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over