2-178714986-C-T

Position:

chr2-178714986-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 5 ACMG points: 5P and 0B. PP2PP3_Strong

The NM_001267550.2(TTN):c.26200G>A(p.Ala8734Thr) variant causes a missense, splice region change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000349 in 1,604,034 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Uncertain significance (★★).

Frequency

Genomes: 𝑓 0.000020 ( 0 hom., cov: 33)

Exomes 𝑓: 0.000037 ( 0 hom. )

Consequence

TTN
NM_001267550.2 missense, splice_region

Scores

Splicing: ADA: 1.000

Clinical Significance

Uncertain significance criteria provided, multiple submitters, no conflicts U:4

Conservation

PhyloP100: 7.91

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 5 ACMG points.

PP2

Missense variant in gene, where missense usually causes diseases (based on misZ statistic), TTN. . Gene score misZ -1.1021 (greater than the threshold 3.09). Trascript score misZ 6.9794 (greater than threshold 3.09). GenCC has associacion of gene with dilated cardiomyopathy, tibial muscular dystrophy, early-onset myopathy with fatal cardiomyopathy, autosomal recessive centronuclear myopathy, hypertrophic cardiomyopathy, hypertrophic cardiomyopathy 9, TTN-related myopathy, dilated cardiomyopathy 1G, arrhythmogenic right ventricular cardiomyopathy, myopathy, myofibrillar, 9, with early respiratory failure, familial isolated dilated cardiomyopathy, childhood-onset progressive contractures-limb-girdle weakness-muscle dystrophy syndrome, autosomal recessive limb-girdle muscular dystrophy type 2J.

PP3

Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF, max_spliceai. No scorers claiming Uncertain. No scorers claiming Benign.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTN	NM_001267550.2 linkuse as main transcript	c.26200G>A	p.Ala8734Thr	missense_variant, splice_region_variant	90/363	ENST00000589042.5

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTN	ENST00000589042.5 linkuse as main transcript	c.26200G>A	p.Ala8734Thr	missense_variant, splice_region_variant	90/363	5	NM_001267550.2	P1
TTN-AS1	ENST00000659121.1 linkuse as main transcript	n.503-19518C>T		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes

AF:

0.0000197

AC:

AN:

152092

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:

0.0000294

Gnomad OTH

AF:

0.00

GnomAD4 exome

AF:

0.0000365

AC:

AN:

1451942

Hom.:

Cov.:

AF XY:

0.0000319

AC XY:

AN XY:

721004

show subpopulations

Gnomad4 AFR exome

AF:

0.00

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:

0.0000470

Gnomad4 OTH exome

AF:

0.0000167

GnomAD4 genome

AF:

0.0000197

AC:

AN:

152092

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

74278

show subpopulations

Gnomad4 AFR

AF:

0.0000241

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:

0.0000294

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.0000329

Hom.:

Bravo

AF:

0.0000113

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:4

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

not specified

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Aug 14, 2013

The Ala7490Thr variant in TTN has not been reported in individuals with cardiomy opathy or in large population studies. Computational analyses (biochemical amino acid properties, conservation, AlignGVGD, PolyPhen2, and SIFT) suggest that thi s amino acid change may not impact the protein, though this information is not p redictive enough to rule out pathogenicity. This variant is located in the last base of the exon, which is part of the 5' splice region. Computational tools do suggest an impact to splicing, though this information is not predictive enough to determine pathogenicity. Additional information is needed to fully assess the clinical significance of this variant. -

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

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Oct 05, 2022

This sequence change replaces alanine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 8734 of the TTN protein (p.Ala8734Thr). This variant also falls at the last nucleotide of exon 90, which is part of the consensus splice site for this exon. This variant is present in population databases (rs727503646, gnomAD 0.007%). This variant has not been reported in the literature in individuals affected with TTN-related conditions. ClinVar contains an entry for this variant (Variation ID: 166149). Experimental studies and prediction algorithms are not available or were not evaluated, and the functional significance of this variant is currently unknown. Variants that disrupt the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. This variant is located in the I band of TTN (PMID: 25589632). Variants in this region may be clinically relevant, but have not been definitively shown to cause cardiomyopathy or neuromuscular disease (PMID: 27493940, 32778822). 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. -

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

Uncertain significance, criteria provided, single submitter

clinical testing

Fulgent Genetics, Fulgent Genetics

Sep 18, 2021

- -

not provided

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Eurofins Ntd Llc (ga)

May 18, 2016

- -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.076

BayesDel_addAF

Benign

-0.15

BayesDel_noAF

Benign

-0.45

CADD

Uncertain

DANN

Benign

0.96

Eigen

Benign

0.064

Eigen_PC

Benign

0.22

FATHMM_MKL

Pathogenic

0.99

LIST_S2

Benign

0.82

T;D;.;T

M_CAP

Benign

0.035

MetaRNN

Benign

0.21

T;T;T;T

MetaSVM

Benign

-1.0

MutationTaster

Benign

0.98

D;D;D;D;D;D

PrimateAI

Benign

0.36

PROVEAN

Benign

-2.1

N;.;.;.

REVEL

Benign

0.084

Sift

Benign

0.11

T;.;.;.

Polyphen

0.0010

.;.;B;B

Vest4

0.37

MVP

0.12

MPC

0.081

ClinPred

0.70

GERP RS

5.0

Splicing

Name

Calibrated prediction

Score

Prediction

dbscSNV1_ADA

Pathogenic

1.0

dbscSNV1_RF

Pathogenic

1.0

SpliceAI score (max)

0.56

Details are displayed if max score is > 0.2

DS_DL_spliceai

0.56

Position offset: 0

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