rs747236787

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1PM2PP5_Very_Strong

The NM_001267550.2(TTN):c.54418C>T(p.Arg18140Ter) variant causes a stop gained change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000214 in 1,400,692 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★). Variant results in nonsense mediated mRNA decay.

Frequency

Genomes: not found (cov: 32)

Exomes 𝑓: 0.0000021 ( 0 hom. )

Consequence

TTN
NM_001267550.2 stop_gained

Scores

Clinical Significance

Likely pathogenic criteria provided, multiple submitters, no conflicts P:4

Conservation

PhyloP100: 2.59

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 Pathogenic. Variant got 18 ACMG points.

PVS1

Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.

PM2

Very rare variant in population databases, with high coverage;

PP5

Variant 2-178604269-G-A is Pathogenic according to our data. Variant chr2-178604269-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 579797.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTN	NM_001267550.2 linkuse as main transcript	c.54418C>T	p.Arg18140Ter	stop_gained	282/363	ENST00000589042.5
TTN-AS1	NR_038272.1 linkuse as main transcript	n.3918-462G>A		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.54418C>T	p.Arg18140Ter	stop_gained	282/363	5	NM_001267550.2	P1
TTN-AS1	ENST00000659121.1 linkuse as main transcript	n.502+6588G>A		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes

Cov.:

GnomAD3 exomes

AF:

0.00000983

AC:

AN:

203450

Hom.:

AF XY:

0.00000920

AC XY:

AN XY:

108640

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:

0.0000209

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000214

AC:

AN:

1400692

Hom.:

Cov.:

AF XY:

0.00000435

AC XY:

AN XY:

689722

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:

9.26e-7

Gnomad4 OTH exome

AF:

0.0000347

GnomAD4 genome

Cov.:

ExAC

AF:

0.0000166

AC:

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

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

Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Invitae

Sep 12, 2022

In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely 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). ClinVar contains an entry for this variant (Variation ID: 579797). This variant has not been reported in the literature in individuals affected with TTN-related conditions. 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. This sequence change creates a premature translational stop signal (p.Arg18140*) in the TTN gene. While this is not anticipated to result in nonsense mediated decay, it is expected to create a truncated TTN protein. -

Dilated cardiomyopathy 1G;C1861065:Hypertrophic cardiomyopathy 9

Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

New York Genome Center

Mar 09, 2023

The c.54418C>T variant identified in TTN has not been reported previously in individuals with titinopathies; it has been reported in ClinVar as Likely pathogenic by three submitters [ClinVar ID: 579797]. The c.54418C>T variant is observed in 2 alleles (~0.0009% minor allele frequency with 0 homozygote) in population databases (gnomAD v2.1.1 and v3.1.2, TOPMed Freeze 8), suggesting it is not a common benign variant in the populations represented in those databases. The c.54418C>T variant is located in exon 282 (A-band) of this 363-exon gene, is predicted to incorporate a premature termination codon (p.(Arg18140Ter), and is expected to result in loss-of-function either through protein truncation or nonsense-mediated mRNA decay. Based on available evidence, this c.54418C>T p.(Arg18140Ter) variant identified in TTN is classified as Likely Pathogenic. -

not provided

Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Apr 02, 2023

Nonsense variant predicted to result in protein truncation or nonsense mediated decay in a gene for which loss-of-function is a known mechanism of disease; Located in the A-band region of TTN in which the majority of loss of function variants have been associated with autosomal dominant titinopathies (Herman et al., 2012); Has not been previously published as pathogenic or benign to our knowledge; Not observed at significant frequency in large population cohorts (gnomAD); This variant is associated with the following publications: (PMID: 22335739) -

Cardiovascular phenotype

Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

May 27, 2022

The p.R9075* variant (also known as c.27223C>T), located in coding exon 109 of the TTN gene, results from a C to T substitution at nucleotide position 27223. This changes the amino acid from an arginine to a stop codon within coding exon 109. This exon 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 alteration is expected to result in loss of function by premature protein truncation or nonsense-mediated mRNA decay. While truncating variants in TTN are present in 1-3% of the general population, truncating variants in the A-band are the most common cause of dilated cardiomyopathy (DCM) (Herman DS et al. N. Engl. J. Med., 2012 Feb;366:619-28; Roberts AM et al. Sci Transl Med, 2015 Jan;7:270ra6). TTN truncating variants encoded in constitutive exons (PSI >90%) have been found to be significantly associated with DCM regardless of their position in titin (Schafer S et al. Nat. Genet., 2017 01;49:46-53). As such, this alteration is classified as likely pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Pathogenic

0.60

BayesDel_noAF

Pathogenic

0.62

Cadd

Pathogenic

Dann

Uncertain

0.99

Eigen

Pathogenic

1.1

Eigen_PC

Pathogenic

0.96

FATHMM_MKL

Uncertain

0.91

MutationTaster

Benign

1.0

A;A;A;A;A;A

Vest4

0.94

GERP RS

5.2

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.030

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