rs757603460

Variant names:

• chr2-178577446-G-GGTAT
• rs757603460
• NM_001267550.2:c.68885_68888dupATAC

Variant summary

Our verdict is Pathogenic. The variant received 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_001267550.2(TTN):​c.68885_68888dupATAC​(p.Ile22964TyrfsTer8) variant causes a frameshift change. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Likely pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: TTN NM_001267550.2 frameshift
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 4.88
• Publications: 1 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]

ENSG00000271011 (HGNC:):

ACMG classification

Our verdict: Pathogenic. The variant received 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 2-178577446-G-GGTAT is Pathogenic according to our data. Variant chr2-178577446-G-GGTAT is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 404732.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 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.68885_68888dupATAC	p.Ile22964TyrfsTer8	frameshift	Exon 324 of 363	NP_001254479.2
	TTN	NM_001256850.1		c.63962_63965dupATAC	p.Ile21323TyrfsTer8	frameshift	Exon 274 of 313	NP_001243779.1
	TTN	NM_133378.4		c.61181_61184dupATAC	p.Ile20396TyrfsTer8	frameshift	Exon 273 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.68885_68888dupATAC	p.Ile22964TyrfsTer8	frameshift	Exon 324 of 363	ENSP00000467141.1
	TTN	ENST00000446966.2	TSL:1	c.68729_68732dupATAC	p.Ile22912TyrfsTer8	frameshift	Exon 322 of 361	ENSP00000408004.2
	TTN	ENST00000436599.2	TSL:1	c.68609_68612dupATAC	p.Ile22872TyrfsTer8	frameshift	Exon 322 of 361	ENSP00000405517.2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD2 exomes AF: 0.00000812 AC: 2 AN: 246420 AF XY: 0.00

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000581

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome Data not reliable, filtered out with message: AS_VQSR AF: 0.00000137 AC: 2 AN: 1454750 Hom.: 0 Cov.: 35 AF XY: 0.00 AC XY: 0 AN XY: 722612

African (AFR) AF: 0.00 AC: 0 AN: 33386

American (AMR) AF: 0.0000448 AC: 2 AN: 44634

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26066

East Asian (EAS) AF: 0.00 AC: 0 AN: 39438

South Asian (SAS) AF: 0.00 AC: 0 AN: 86134

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 51610

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5740

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1107630

Other (OTH) AF: 0.00 AC: 0 AN: 60112

GnomAD4 genome Cov.: 32

ClinVar

ClinVar submissions as Germline

Significance: Pathogenic/Likely pathogenic

Revision: criteria provided, multiple submitters, no conflicts

Pathogenic	VUS	Benign	Condition
2	-	-	not provided (2)
1	-	-	Autosomal recessive limb-girdle muscular dystrophy type 2J;C1858763:Dilated cardiomyopathy 1G (1)
1	-	-	Cardiovascular phenotype (1)

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
PhyloP100		4.9
Mutation Taster		=0/200	disease causing (ClinVar)

Splicing

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs757603460; hg19: chr2-179442173;