2-178589733-G-C

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.61992C>G(p.Asn20664Lys) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000508 in 1,613,436 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 13/20 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another nucleotide change resulting in the same amino acid substitution has been previously reported as Uncertain significance in ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. N20664H) has been classified as Uncertain significance.

Frequency

Genomes: 𝑓 0.000053 ( 0 hom., cov: 33)

Exomes 𝑓: 0.000051 ( 0 hom. )

Consequence

TTN
NM_001267550.2 missense

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:3B:1

Conservation

PhyloP100: 2.03

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:

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=0.16839352).

BP6

Variant 2-178589733-G-C is Benign according to our data. Variant chr2-178589733-G-C is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 179045.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTN	NM_001267550.2 link	c.61992C>G	p.Asn20664Lys	missense_variant	Exon 304 of 363	ENST00000589042.5	NP_001254479.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5 link	c.61992C>G	p.Asn20664Lys	missense_variant	Exon 304 of 363	5	NM_001267550.2	ENSP00000467141.1

Frequencies

GnomAD3 genomes

AF:

0.0000526

AC:

AN:

152088

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000241

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

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:

0.00

GnomAD2 exomes

AF:

0.0000201

AC:

AN:

248482

AF XY:

0.0000297

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.0000445

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000506

AC:

AN:

1461348

Hom.:

Cov.:

AF XY:

0.0000509

AC XY:

AN XY:

726960

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

33448

American (AMR)

AF:

0.00

AC:

AN:

44714

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26126

East Asian (EAS)

AF:

0.00

AC:

AN:

39672

South Asian (SAS)

AF:

0.00

AC:

AN:

86246

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53400

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5758

European-Non Finnish (NFE)

AF:

0.0000612

AC:

AN:

1111630

Other (OTH)

AF:

0.0000994

AC:

AN:

60354

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.464

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:

0.0000526

AC:

AN:

152088

Hom.:

Cov.:

AF XY:

0.0000539

AC XY:

AN XY:

74274

show subpopulations

African (AFR)

AF:

0.0000241

AC:

AN:

41456

American (AMR)

AF:

0.00

AC:

AN:

15268

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3472

East Asian (EAS)

AF:

0.00

AC:

AN:

5144

South Asian (SAS)

AF:

0.00

AC:

AN:

4822

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10626

Middle Eastern (MID)

AF:

0.00

AC:

AN:

316

European-Non Finnish (NFE)

AF:

0.000103

AC:

AN:

67982

Other (OTH)

AF:

0.00

AC:

AN:

2090

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.488

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:

0.00

Hom.:

Bravo

AF:

0.0000604

TwinsUK

AF:

0.00

AC:

ALSPAC

AF:

0.000259

AC:

ESP6500AA

AF:

0.00

AC:

ESP6500EA

AF:

0.000244

AC:

ExAC

AF:

0.0000248

AC:

EpiCase

AF:

0.000218

EpiControl

AF:

0.00

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:3Benign:1

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

not specified

Uncertain:1

Nov 14, 2013

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

The Asn18096Lys variant in TTN has not been previously reported in individuals w ith cardiomyopathy, but has been identified in 2/8212 European American chromoso mes by the NHLBI Exome Sequencing Project (http://evs.gs.washington.edu; dbSNP r s376455983). Computational analyses (amino acid biochemical properties, conserv ation, PolyPhen-2, AlignGVGD, SIFT) do not provide strong evidence for or agains t an impact to the protein. Additional information is needed to fully assess the clinical significance of the Asn18096Lys variant. -

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

Uncertain:1

May 06, 2018

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

This sequence change replaces asparagine with lysine at codon 20664 of the TTN protein (p.Asn20664Lys). There is a moderate physicochemical difference between asparagine and lysine. This variant is present in population databases (rs376455983, ExAC 0.004%). This variant has not been reported in the literature in individuals with TTN-related disease. ClinVar contains an entry for this variant (Variation ID: 179045). This variant is located in the A band of TTN (PMID: 25589632). Variants in this region may be relevant for cardiac or neuromuscular disorders (PMID: 25589632, 23975875). Algorithms developed to predict the effect of missense changes on protein structure and function are unavailable for the TTN gene. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site, but this prediction has not been confirmed by published transcriptional studies. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Cardiovascular phenotype

Uncertain:1

Sep 11, 2020

Ambry Genetics

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

The p.N11599K variant (also known as c.34797C>G), located in coding exon 131 of the TTN gene, results from a C to G substitution at nucleotide position 34797. The asparagine at codon 11599 is replaced by lysine, an amino acid with similar properties. This amino acid position is poorly conserved in available vertebrate species. In addition, this alteration is predicted to be tolerated by in silico analysis. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

not provided

Benign:1

Jun 26, 2019

GeneDx

Significance:Likely benign

Review Status:criteria provided, single submitter

Collection Method:clinical testing

See Variant Classification Assertion Criteria. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Pathogenic

0.71

BayesDel_addAF

Benign

-0.28

BayesDel_noAF

Benign

-0.48

CADD

Benign

(source)

DANN

Benign

0.95

Eigen

Benign

0.10

Eigen_PC

Benign

0.14

FATHMM_MKL

Uncertain

0.92

LIST_S2

Uncertain

0.92

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

M_CAP

Benign

0.014

MetaRNN

Benign

0.17

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

MetaSVM

Benign

-1.0

MutationAssessor

Uncertain

2.1

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

PhyloP100

2.0

PrimateAI

Uncertain

0.76

PROVEAN

Uncertain

-3.5

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

REVEL

Benign

0.18

Sift

Uncertain

0.025

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

Polyphen

0.92

.;.;.;P;.;.;P

Vest4

0.43

MutPred

0.53

.;.;.;Gain of methylation at N19023 (P = 0.0122);.;.;Gain of methylation at N19023 (P = 0.0122);

MVP

0.17

MPC

0.22

ClinPred

0.44

GERP RS

2.0

Mutation Taster

=51/49

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