rs774414270
Positions:
Variant summary
Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PVS1_ModeratePM2PP3_Strong
The NM_001267550.2(TTN):c.1938+1G>T variant causes a splice donor change. The variant allele was found at a frequency of 0.000000685 in 1,460,530 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic 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: not found (cov: 32)
Exomes 𝑓: 6.8e-7 ( 0 hom. )
Consequence
TTN
NM_001267550.2 splice_donor
NM_001267550.2 splice_donor
Scores
4
2
1
Splicing: ADA: 1.000
2
Clinical Significance
Conservation
PhyloP100: 3.64
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]
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ACMG classification
Classification made for transcript
Verdict is Likely_pathogenic. Variant got 8 ACMG points.
PVS1
Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.0012688005 fraction of the gene. No cryptic splice site detected. Exon removal is inframe change.
PM2
Very rare variant in population databases, with high coverage;
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 | c.1938+1G>T | splice_donor_variant | ENST00000589042.5 | |||
TTN | NM_133379.5 | c.1938+1G>T | splice_donor_variant | ENST00000360870.10 |
Ensembl
Gene | Transcript | HGVSc | HGVSp | Effect | #exon/exons | TSL | MANE | Appris | UniProt |
---|---|---|---|---|---|---|---|---|---|
TTN | ENST00000360870.10 | c.1938+1G>T | splice_donor_variant | 5 | NM_133379.5 | ||||
TTN | ENST00000589042.5 | c.1938+1G>T | splice_donor_variant | 5 | NM_001267550.2 | P1 |
Frequencies
GnomAD3 genomes Cov.: 32
GnomAD3 genomes
Cov.:
32
GnomAD4 exome AF: 6.85e-7 AC: 1AN: 1460530Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1AN XY: 726622
GnomAD4 exome
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GnomAD4 genome Cov.: 32
GnomAD4 genome
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32
ExAC
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1
ClinVar
Significance: Uncertain significance
Submissions summary: Uncertain:2
Revision: criteria provided, multiple submitters, no conflicts
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 | Jan 04, 2022 | 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. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. ClinVar contains an entry for this variant (Variation ID: 466867). This variant has not been reported in the literature in individuals affected with TTN-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change affects a donor splice site in intron 12 of the TTN gene. It is expected to disrupt RNA splicing. Variants that disrupt the donor or acceptor splice site typically lead to a loss of protein function (PMID: 16199547), however the current clinical and genetic evidence is not sufficient to establish whether loss-of-function variants in TTN cause disease. - |
not provided Uncertain:1
Uncertain significance, criteria provided, single submitter | clinical testing | Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine | Dec 01, 2023 | The c.1938+1G>T variant in TTN has not been previously reported in individuals with cardiomyopathy and was absent from large population studies. This variant has also been reported in ClinVar (Variation ID 466867). This variant occurs within the canonical splice site (+1) and is predicted to cause altered splicing leading to an abnormal or absent protein. This variant is predicted to cause in-frame exon skipping of exon 12 (less than 10% of the protein), which has a 79% PSI. In summary, the clinical significance of this variant is uncertain. ACMG/AMP Criteria applied: PVS1_Moderate, PM2_Supporting. - |
Computational scores
Source:
Name
Calibrated prediction
Score
Prediction
BayesDel_addAF
Pathogenic
D
BayesDel_noAF
Pathogenic
CADD
Pathogenic
DANN
Uncertain
Eigen
Pathogenic
Eigen_PC
Pathogenic
FATHMM_MKL
Uncertain
D
MutationTaster
Benign
D;D;D;D;D;D;D
GERP RS
Splicing
Name
Calibrated prediction
Score
Prediction
dbscSNV1_ADA
Pathogenic
dbscSNV1_RF
Pathogenic
SpliceAI score (max)
Details are displayed if max score is > 0.2
DS_DL_spliceai
Position offset: 1
Find out detailed SpliceAI scores and Pangolin per-transcript scores at