rs878854432

Variant names:

• chr2-178544074-C-CA
• rs878854432
• NM_001267550.2:c.96069dupT

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 12P and 0B. PVS1 PM2 PP5_Moderate

The NM_001267550.2(TTN):​c.96069dupT​(p.Val32024CysfsTer31) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,461,070 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Likely pathogenic (★). Synonymous variant affecting the same amino acid position (i.e. T32023T) has been classified as Likely benign. Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: TTN NM_001267550.2 frameshift
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:2
• Conservation: PhyloP100: -0.251
• Publications: 0 publications found

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]

ACMG classification

Our verdict: Pathogenic. The variant received 12 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 2-178544074-C-CA is Pathogenic according to our data. Variant chr2-178544074-C-CA is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 238870.Status of the report is criteria_provided_single_submitter, 1 stars.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_001267550.2. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TTN	NM_001267550.2	MANE Select	c.96069dupT	p.Val32024CysfsTer31	frameshift	Exon 346 of 363	NP_001254479.2
	TTN	NM_001256850.1		c.91146dupT	p.Val30383CysfsTer31	frameshift	Exon 296 of 313	NP_001243779.1
	TTN	NM_133378.4		c.88365dupT	p.Val29456CysfsTer31	frameshift	Exon 295 of 312	NP_596869.4

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TTN	ENST00000589042.5	TSL:5 MANE Select	c.96069dupT	p.Val32024CysfsTer31	frameshift	Exon 346 of 363	ENSP00000467141.1
	TTN	ENST00000446966.2	TSL:1	c.95913dupT	p.Val31972CysfsTer31	frameshift	Exon 344 of 361	ENSP00000408004.2
	TTN	ENST00000436599.2	TSL:1	c.95793dupT	p.Val31932CysfsTer31	frameshift	Exon 344 of 361	ENSP00000405517.2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461070 Hom.: 0 Cov.: 33 AF XY: 0.00000138 AC XY: 1 AN XY: 726780

African (AFR) AF: 0.00 AC: 0 AN: 33460

American (AMR) AF: 0.00 AC: 0 AN: 44700

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26100

East Asian (EAS) AF: 0.00 AC: 0 AN: 39690

South Asian (SAS) AF: 0.00 AC: 0 AN: 86220

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53348

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5760

European-Non Finnish (NFE) AF: 0.00000180 AC: 2 AN: 1111452

Other (OTH) AF: 0.00 AC: 0 AN: 60340

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, single submitter

Submissions by phenotype

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

Jan 01, 2016

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

For these reasons, this variant has been classified as Likely Pathogenic. This variant is found in the A-band of this gene. While this particular variant has not been reported in the literature, truncating variants in the A-band of TTN are likely pathogenic (PMID: 25589632). This sequence change duplicates 1 nucleotide in exon 346 of the TTN mRNA (c.96069dupT), causing a frameshift at codon 32024. This creates a premature translational stop signal (p.Val32024Cysfs*31) and is expected to result in an absent or disrupted protein product.

Dilated cardiomyopathy 1G Pathogenic:1

Jan 01, 2016

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change duplicates 1 nucleotide in exon 346 of the TTN mRNA (c.96069dupT), causing a frameshift at codon 32024. This creates a premature translational stop signal (p.Val32024Cysfs*31) and is expected to result in an absent or disrupted protein product. This variant is found in the A-band of this gene. While this particular variant has not been reported in the literature, truncating variants in the A-band of TTN are likely pathogenic (PMID: 25589632). For these reasons, this variant has been classified as Likely Pathogenic.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
PhyloP100		-0.25

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

Other links and lift over

dbSNP: rs878854432; hg19: chr2-179408801;