chr2-178542263-C-T

Position:

chr2-178542263-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 5 ACMG points: 5P and 0B. PVS1_ModeratePM2PP5

The NM_001267550.2(TTN):c.97492+1G>A variant causes a splice donor, intron change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000187 in 1,603,430 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 1/1 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

Frequency

Genomes: 𝑓 0.0000066 ( 0 hom., cov: 32)

Exomes 𝑓: 0.0000014 ( 0 hom. )

Consequence

TTN
NM_001267550.2 splice_donor, intron

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2U:1

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:):

TTN-AS1 links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Uncertain_significance. Variant got 5 ACMG points.

PVS1

Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.0027691338 fraction of the gene. No cryptic splice site detected. Exon removal is inframe change.

PM2

Very rare variant in population databases, with high coverage;

PP5

Variant 2-178542263-C-T is Pathogenic according to our data. Variant chr2-178542263-C-T is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 1393545.We mark this variant Likely_pathogenic, oryginal submissions are: {Pathogenic=1, Uncertain_significance=1}. Variant chr2-178542263-C-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTN	NM_001267550.2 linkuse as main transcript	c.97492+1G>A		splice_donor_variant, intron_variant		ENST00000589042.5	NP_001254479.2	A0A0A0MTS7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5 linkuse as main transcript	c.97492+1G>A		splice_donor_variant, intron_variant		5	NM_001267550.2	ENSP00000467141.1		A0A0A0MTS7

Frequencies

GnomAD3 genomes

AF:

0.00000657

AC:

AN:

152092

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.0000656

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:

0.00000419

AC:

AN:

238604

Hom.:

AF XY:

0.00

AC XY:

AN XY:

129360

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 SAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00000931

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000138

AC:

AN:

1451338

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

720416

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:

0.0000189

Gnomad4 NFE exome

AF:

9.05e-7

Gnomad4 OTH exome

AF:

0.00

GnomAD4 genome

AF:

0.00000657

AC:

AN:

152092

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

74290

show subpopulations

Gnomad4 AFR

AF:

0.00

Gnomad4 AMR

AF:

0.0000656

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

Bravo

AF:

0.00000378

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2Uncertain:1

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

TTN-related disorder

Pathogenic:1

Pathogenic, no assertion criteria provided

clinical testing

PreventionGenetics, part of Exact Sciences

Apr 12, 2024

The TTN c.97492+1G>A variant is predicted to disrupt the GT donor site and interfere with normal splicing. This variant has been reported in individuals with dilated cardiomyopathy (eTable 2 in Corden et al. 2019. PubMed ID: 31251381; reported with the genomic coordinate chr2:179406990 C>T in Table S1, Ware et al. 2016. PubMed ID: 26735901 and Jansen et al. 2019. PubMed ID: 31112426). A different variant at the same position has also been reported in an individual with dilated cardiomyopathy (reported with the genomic coordinate chr2:179406990 C>G in Table S1, Ware et al. 2016. PubMed ID: 26735901). This variant is reported in 0.00093% of alleles in individuals of European (Non-Finnish) descent in gnomAD. This variant is located in the A-band region of the TTN protein in which truncating TTN variants have been found more frequently in dilated cardiomyopathy patients than in controls (Herman et al. 2012. PubMed ID: 22335739). RNAseq studies from heart tissue indicate the adjacent exon is commonly included in TTN mRNA transcripts (PSI of 100%, Roberts et al. 2015. PubMed ID: 25589632; https://www.cardiodb.org/titin/titin_exon.php?id=309). TTN truncating variants are reported in 1-2% of presumably healthy individuals, but occur more frequently in exons with low PSI values (Roberts et al. 2015. PubMed ID: 25589632; Herman et al. 2012. PubMed ID: 22335739). Many cases of severe recessive TTN-related myopathies in which the individual is compound heterozygous for two loss of function variants in TTN have also been reported (See Ceyhan-Birsoy et al. 2013. PubMed ID: 23975875; Chauveau et al. 2014. PubMed ID: 24105469; Evilä et al. 2016. PubMed ID:27796757; Ge et al. 2019. PubMed ID: 31053406; Oates et al. 2018. PubMed ID: 29691892; Bryen et al. 2020. PubMed ID: 31660661). In summary, we classify this variant as pathogenic. Of note, this variant is considered pathogenic for increased risk of TTN-related cardiac disorders, and also for autosomal recessive severe congenital titinopathies when in the presence of an additional loss-of-function TTN variant. -

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

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Nov 02, 2021

This sequence change affects a donor splice site in intron 349 of the TTN gene. It is expected to disrupt RNA splicing and likely results in a truncated or disrupted TTN protein. The frequency data for this variant in the population databases is considered unreliable, as metrics indicate poor data quality at this position in the gnomAD database. For these reasons, this variant has been classified as Pathogenic. This variant is located in the A band of TTN (PMID: 25589632). Truncating variants in this region are significantly overrepresented in patients affected with dilated cardiomyopathy (PMID: 25589632). Truncating variants in this region have also been reported in individuals affected with autosomal recessive centronuclear myopathy (PMID: 23975875). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. Disruption of this splice site has been observed in individuals with dilated cardiomyopathy (PMID: 22335739). -

Cardiovascular phenotype

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Jan 24, 2024

The c.70297+1G>A intronic variant results from a G to A substitution one nucleotide after coding exon 176 of the TTN gene. Exon 176 is located in the A-band region of the N2-B isoform of the titin protein and is constitutively expressed in TTN transcripts (percent spliced in or PSI 100%). This nucleotide position is highly conserved in available vertebrate species. In silico splice site analysis predicts that this alteration will weaken the native splice donor site. This alteration disrupts the canonical splice site and is expected to cause aberrant splicing. However, although direct evidence is unavailable, this alteration is predicted to result in an in-frame transcript that is not expected to trigger nonsense-mediated mRNA decay. The exact functional effect of the predicted splice impact is unknown. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Pathogenic

0.47

BayesDel_noAF

Pathogenic

0.44

CADD

Pathogenic

DANN

Uncertain

0.99

Eigen

Pathogenic

1.2

Eigen_PC

Pathogenic

1.1

FATHMM_MKL

Pathogenic

1.0

MutationTaster

Benign

1.0

D;D;D;D;D;D

GERP RS

6.2

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.7

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.99

Details are displayed if max score is > 0.2

DS_DL_spliceai

0.99

Position offset: 1

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