rs1025426023

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 3P and 1B. PM2PP2BP4

The NM_001267550.2(TTN):c.56051G>A(p.Cys18684Tyr) variant causes a missense, splice region change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000323 in 1,547,022 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. 3/3 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. C18684R) has been classified as Uncertain significance.

Frequency

Genomes: 𝑓 0.000020 ( 0 hom., cov: 32)

Exomes 𝑓: 0.0000014 ( 0 hom. )

Consequence

TTN
NM_001267550.2 missense, splice_region

Scores

Splicing: ADA: 0.9390

Clinical Significance

Uncertain significance criteria provided, single submitter U:1

Conservation

PhyloP100: 7.76

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 made for transcript

Verdict is Uncertain_significance. Variant got 2 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

PP2

Missense variant where missense usually causes diseases, TTN

BP4

Computational evidence support a benign effect (MetaRNN=0.37362605).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTN	NM_001267550.2 linkuse as main transcript	c.56051G>A	p.Cys18684Tyr	missense_variant, splice_region_variant	289/363	ENST00000589042.5
TTN-AS1	NR_038272.1 linkuse as main transcript	n.3725+100C>T		intron_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTN	ENST00000589042.5 linkuse as main transcript	c.56051G>A	p.Cys18684Tyr	missense_variant, splice_region_variant	289/363	5	NM_001267550.2	P1
TTN-AS1	ENST00000659121.1 linkuse as main transcript	n.502+2169C>T		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes

AF:

0.0000198

AC:

AN:

151804

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000726

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:

0.00

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000150

AC:

AN:

199838

Hom.:

AF XY:

0.0000276

AC XY:

AN XY:

108582

show subpopulations

Gnomad AFR exome

AF:

0.000139

Gnomad AMR exome

AF:

0.0000438

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad SAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000143

AC:

AN:

1395218

Hom.:

Cov.:

AF XY:

0.00000290

AC XY:

AN XY:

688966

show subpopulations

Gnomad4 AFR exome

AF:

0.0000659

Gnomad4 AMR exome

AF:

0.00

Gnomad4 ASJ exome

AF:

0.00

Gnomad4 EAS exome

AF:

0.00

Gnomad4 SAS exome

AF:

0.00

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

0.00

Gnomad4 OTH exome

AF:

0.00

GnomAD4 genome

AF:

0.0000198

AC:

AN:

151804

Hom.:

Cov.:

AF XY:

0.0000135

AC XY:

AN XY:

74086

show subpopulations

Gnomad4 AFR

AF:

0.0000726

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.00

Gnomad4 OTH

AF:

0.00

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

LINK: link

Submissions by phenotype

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

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

May 09, 2017

This sequence change replaces cysteine with tyrosine at codon 18684 of the TTN protein (p.Cys18684Tyr). Conservation data is not available for the cysteine residue and there is a large physicochemical difference between cysteine and tyrosine. This variant also falls at the first nucleotide of exon 289 of the TTN coding sequence, which is part of the consensus splice site for this exon. This variant is not present in population databases (ExAC no frequency) and has not been reported in the literature in individuals with a TTN-related disease. This variant identified in the TTN gene is located in the A-band of the resulting protein (PMID: 25589632). Experimental studies and prediction algorithms are not available for this variant, and it is unclear how this variant impacts the function of this protein. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may alter RNA splicing, but this prediction has not been confirmed by published transcriptional studies. In summary, this variant is a novel missense change with uncertain impact on RNA splicing and protein function. It has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.21

BayesDel_addAF

Benign

-0.17

BayesDel_noAF

Benign

-0.23

Cadd

Benign

Dann

Benign

0.86

Eigen

Pathogenic

0.75

Eigen_PC

Pathogenic

0.77

FATHMM_MKL

Pathogenic

1.0

LIST_S2

Uncertain

0.87

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

M_CAP

Benign

0.048

MetaRNN

Benign

0.37

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

MetaSVM

Benign

-0.47

MutationTaster

Benign

1.0

D;D;D;D;D;D

PrimateAI

Uncertain

0.77

PROVEAN

Pathogenic

-7.1

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

REVEL

Uncertain

0.36

Sift

Benign

0.51

T;T;.;.;T;T;.

Vest4

0.56

MutPred

0.32

Gain of methylation at K16112 (P = 0.0426);.;.;.;.;.;.;

MVP

0.73

ClinPred

0.23

GERP RS

5.8

Splicing

Name

Calibrated prediction

Score

Prediction

dbscSNV1_ADA

Benign

0.94

dbscSNV1_RF

Benign

0.56

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

LitVar

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over