chr2-178745884-C-A

Variant names:

Variant summary

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

The NM_133379.5(TTN):c.16516G>T(p.Glu5506*) variant causes a stop gained change. The variant allele was found at a frequency of 0.0000839 in 1,609,784 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 Uncertain significance (★★).

Frequency

Genomes: 𝑓 0.000046 ( 0 hom., cov: 32)

Exomes 𝑓: 0.000088 ( 1 hom. )

Consequence

TTN
NM_133379.5 stop_gained

Scores

Clinical Significance

Uncertain significance criteria provided, multiple submitters, no conflicts U:6

Conservation

PhyloP100: 5.11

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 0 ACMG points.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTN	NM_133379.5 link	c.16516G>T	p.Glu5506*	stop_gained	Exon 46 of 46	ENST00000360870.10	NP_596870.2	Q8WZ42-6Q7Z3B7
TTN	NM_001267550.2 link	c.11312-3963G>T		intron_variant	Intron 47 of 362	ENST00000589042.5	NP_001254479.2	A0A0A0MTS7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000360870.10 link	c.16516G>T	p.Glu5506*	stop_gained	Exon 46 of 46	5	NM_133379.5	ENSP00000354117.4		Q8WZ42-6
TTN	ENST00000589042.5 link	c.11312-3963G>T		intron_variant	Intron 47 of 362	5	NM_001267550.2	ENSP00000467141.1		A0A0A0MTS7

Frequencies

GnomAD3 genomes

AF:

0.0000461

AC:

AN:

151888

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.0000657

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:

0.0000884

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000608

AC:

AN:

246836

Hom.:

AF XY:

0.0000600

AC XY:

AN XY:

133320

show subpopulations

Gnomad AFR exome

AF:

0.0000619

Gnomad AMR exome

AF:

0.00

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:

0.000125

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000878

AC:

128

AN:

1457896

Hom.:

Cov.:

AF XY:

0.0000855

AC XY:

AN XY:

725112

show subpopulations

Gnomad4 AFR exome

AF:

0.0000302

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:

0.000106

Gnomad4 OTH exome

AF:

0.000133

GnomAD4 genome

AF:

0.0000461

AC:

AN:

151888

Hom.:

Cov.:

AF XY:

0.0000270

AC XY:

AN XY:

74156

show subpopulations

Gnomad4 AFR

AF:

0.00

Gnomad4 AMR

AF:

0.0000657

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.0000884

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.000143

Hom.:

Bravo

AF:

0.0000680

TwinsUK

AF:

0.00

AC:

ALSPAC

AF:

0.000259

AC:

ESP6500AA

AF:

0.000227

AC:

ESP6500EA

AF:

0.000582

AC:

ExAC

AF:

0.0000330

AC:

EpiCase

AF:

0.000164

EpiControl

AF:

0.00

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:6

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

not specified

Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Jan 16, 2025	Variant summary: TTN NM_133378:c.10360+7240G>T is located at a position not widely known to affect splicing. This variant corresponds to c.11312-3963G>T in NM_001267550 and NM_133379:c.16516G>T p.Glu5506X, however nonsense mediated decay is not expected. Loss of function variants in all TTN bands are strongly associated with a spectrum of autosomal recessive titinopathies when exon expression (proportion spliced in, PSI, 1=complete expression) in skeletal muscle is >0.1 (PMID: 36977548, 39198997, 29598826, 32778822, 29691892, 33449170, 36977548, internal data). In contrast, loss of function variants in all TTN bands are only strongly associated with autosomal dominant TTN-related cardiomyopathies if located in exons constitutively expressed (PSI >0.9) in cardiac muscle, excluding extreme C-terminal exons 359-363 (PMID: 25589632, 31216868, 32964742, 34662387, 27869827, Shetty et al., Nat Cardiovasc Res 2024, cardiodb.org, internal data). This variant has a maximum skeletal muscle PSI of 0.02 and a maximum cardiac muscle PSI of 0.035. Consensus agreement among computation tools predict no significant impact on normal splicing. However, these predictions have yet to be confirmed by functional studies. The variant allele was found at a frequency of 6.4e-05 in 330022 control chromosomes. This frequency is not significantly higher than estimated for a pathogenic variant in TTN causing Autosomal Recessive Titinopathy (6.4e-05 vs 0.00039), allowing no conclusion about variant significance. c.10360+7240G>T has been reported in the literature in individuals affected with clinical features of cardiomyopathy without strong evidence for causality (Jurgens_2022) and wad not enriched in the Atrial Fibrillation cohort from the UK Biobank (Connell_2021). These report(s) do not provide unequivocal conclusions about association of the variant with Autosomal Recessive Titinopathy and other TTN-related diseaes. 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: 31691645, 35177841, 33226272). ClinVar contains an entry for this variant (Variation ID: 166247). Based on the evidence outline above, and the lack of clinical evidence in a low PSI exon, the variant has been classified as uncertain significance. -
Uncertain significance, criteria provided, single submitter	clinical testing	Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine	Jan 25, 2019	Variant classified as Uncertain Significance - Favor Benign. The p.Glu5506X variant in TTN has not been previously reported in individuals with cardiomyopathy, but has been identified in 5/8598 of European American chromosomes by the NHLBI Exome Sequencing Project (http://evs.gs.washington.edu/EVS/; dbSNP rs148430495). This variant is located in the last exon of an alternative transcript (Novex-3) and is expected to result in a truncated protein. Although truncating variants in the TTN gene are common in individuals with DCM (Herman 2012), the role of the Novex-3 transcript in cardiomyopathy is unclear. In summary, additional information is needed to fully assess the clinical significance of the Glu5506X variant. -

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 08, 2021

- -

not provided

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Eurofins Ntd Llc (ga)

Nov 28, 2017

- -

Tibial muscular dystrophy

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Centre for Mendelian Genomics, University Medical Centre Ljubljana

Oct 02, 2019

This variant was classified as: Uncertain significance. The available evidence on this variant's pathogenicity is insufficient or conflicting. The following ACMG criteria were applied in classifying this variant: No criteria apply. -

Primary dilated cardiomyopathy

Uncertain:1

Uncertain significance, criteria provided, single submitter

research

Cardiovascular Biomedical Research Unit, Royal Brompton & Harefield NHS Foundation Trust

Oct 08, 2014

This TTN truncating variant (TTNtv) was identified in three individuals in this cohort. It affects only the Novex-3 isoform, which does not span the sarcomere and has not been implicated in DCM. In the seven cohorts assessed, TTNtv were found in 14% of ambulant DCM, 22% end-stage or familial DCM, and 2% controls. Heterozygous nonsense, frameshift and canonical splice-disrupting variants found in constitutive and other highly utilised exons are highly likely to be pathogenic when identified in individuals with phenotypically confirmed DCM. TTNtv found incidentally in healthy individuals (excluding familial assessment of DCM relatives) are thought to have low penetrance, particularly when identified in exons that are not constitutively expressed in the heart. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Benign

-0.15

BayesDel_noAF

Benign

-0.25

CADD

Benign

DANN

Uncertain

0.99

Eigen

Uncertain

0.39

Eigen_PC

Uncertain

0.49

FATHMM_MKL

Uncertain

0.97

Vest4

0.46

GERP RS

5.9

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

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