rs376018437
Variant summary
Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PVS1_ModeratePP3_Strong
The NM_001267550.2(TTN):c.32554+1G>T variant causes a splice donor change. The variant allele was found at a frequency of 0.00000374 in 1,602,780 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: 𝑓 0.0000066 ( 0 hom., cov: 32)
Exomes 𝑓: 0.0000034 ( 0 hom. )
Consequence
TTN
NM_001267550.2 splice_donor
NM_001267550.2 splice_donor
Scores
5
1
1
Splicing: ADA: 1.000
2
Clinical Significance
Conservation
PhyloP100: 5.51
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-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]
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ACMG classification
Classification made for transcript
Verdict is Likely_pathogenic. Variant got 6 ACMG points.
PVS1
?
Splicing variant, NOT destroyed by nmd, known LOF gene, truncates exone, which is 7.686893E-4 fraction of the gene. Cryptic splice site detected, with MaxEntScore 6, offset of -16, new splice context is: aagGTgccc. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in inframe change.
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.32554+1G>T | splice_donor_variant | ENST00000589042.5 | |||
LOC124906100 | XR_007087318.1 | n.2186-28849C>A | intron_variant, non_coding_transcript_variant |
Ensembl
Gene | Transcript | HGVSc | HGVSp | Effect | #exon/exons | TSL | MANE | Appris | UniProt |
---|---|---|---|---|---|---|---|---|---|
TTN | ENST00000589042.5 | c.32554+1G>T | splice_donor_variant | 5 | NM_001267550.2 | P1 | |||
TTN-AS1 | ENST00000659121.1 | n.503-49599C>A | intron_variant, non_coding_transcript_variant |
Frequencies
GnomAD3 genomes ? AF: 0.00000658 AC: 1AN: 151980Hom.: 0 Cov.: 32
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GnomAD3 exomes AF: 0.00000854 AC: 2AN: 234246Hom.: 0 AF XY: 0.00000788 AC XY: 1AN XY: 126952
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GnomAD4 exome AF: 0.00000345 AC: 5AN: 1450800Hom.: 0 Cov.: 31 AF XY: 0.00000139 AC XY: 1AN XY: 720902
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ClinVar
Significance: Uncertain significance
Submissions summary: Uncertain:3
Revision: criteria provided, single submitter
LINK: link
Submissions by phenotype
not provided Uncertain:2
Uncertain significance, no assertion criteria provided | clinical testing | Clinical Genetics DNA and cytogenetics Diagnostics Lab, Erasmus MC, Erasmus Medical Center | - | - - |
Uncertain significance, no assertion criteria provided | clinical testing | Joint Genome Diagnostic Labs from Nijmegen and Maastricht, Radboudumc and MUMC+ | - | - - |
Autosomal recessive limb-girdle muscular dystrophy type 2J;C1858763:Dilated cardiomyopathy 1G Uncertain:1
Uncertain significance, criteria provided, single submitter | clinical testing | Invitae | Sep 19, 2023 | This variant has not been reported in the literature in individuals affected with TTN-related conditions. This sequence change affects a donor splice site in intron 130 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. ClinVar contains an entry for this variant (Variation ID: 658232). 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). Truncating variants in this region have been shown to be highly prevalent in the general population and unaffected individuals (PMID: 26701604, 22335739). However, truncating variants in this region have also been reported in individuals affected with autosomal recessive centronuclear myopathy (PMID: 23975875). 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. - |
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
Pathogenic
D
MutationTaster
Benign
D;D;D;D;D;D
GERP RS
Splicing
Name
Calibrated prediction
Score
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dbscSNV1_ADA
Pathogenic
dbscSNV1_RF
Pathogenic
SpliceAI score (max)
Details are displayed if max score is > 0.2
DS_DG_spliceai
Position offset: 17
DS_DL_spliceai
Position offset: 1
Find out detailed SpliceAI scores and Pangolin per-transcript scores at