rs778392667

Variant names:

• chr2-178733340-AG-A
• rs778392667
• NM_001267550.2:c.15952delC

Variant summary

Our verdict is Likely pathogenic. The variant received 8 ACMG points: 8P and 0B. PVS1

The NM_001267550.2(TTN):​c.15952delC​(p.Leu5318SerfsTer34) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000753 in 1,461,522 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★). Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000075 (0 hom.)
• Consequence: TTN NM_001267550.2 frameshift
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 2.91
• 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: Likely_pathogenic. The variant received 8 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.

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

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TTN	NM_001267550.2	MANE Select	c.15952delC	p.Leu5318SerfsTer34	frameshift	Exon 54 of 363	NP_001254479.2	Q8WZ42-12
	TTN	NM_001256850.1		c.15001delC	p.Leu5001SerfsTer34	frameshift	Exon 52 of 313	NP_001243779.1	Q8WZ42-1
	TTN	NM_133378.4		c.12220delC	p.Leu4074SerfsTer34	frameshift	Exon 51 of 312	NP_596869.4	Q8WZ42-11

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TTN	ENST00000589042.5	TSL:5 MANE Select	c.15952delC	p.Leu5318SerfsTer34	frameshift	Exon 54 of 363	ENSP00000467141.1	Q8WZ42-12
	TTN	ENST00000446966.2	TSL:1	c.15952delC	p.Leu5318SerfsTer34	frameshift	Exon 54 of 361	ENSP00000408004.2	A0A1B0GXE3
	TTN	ENST00000436599.2	TSL:1	c.15676delC	p.Leu5226SerfsTer34	frameshift	Exon 52 of 361	ENSP00000405517.2	A0A0C4DG59

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD2 exomes AF: 0.00000402 AC: 1 AN: 248516 AF XY: 0.00

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 FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000889

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000753 AC: 11 AN: 1461522 Hom.: 0 Cov.: 36 AF XY: 0.00000413 AC XY: 3 AN XY: 727042

African (AFR) AF: 0.00 AC: 0 AN: 33470

American (AMR) AF: 0.00 AC: 0 AN: 44712

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26130

East Asian (EAS) AF: 0.00 AC: 0 AN: 39674

South Asian (SAS) AF: 0.00 AC: 0 AN: 86246

European-Finnish (FIN) AF: 0.0000375 AC: 2 AN: 53392

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5762

European-Non Finnish (NFE) AF: 0.00000720 AC: 8 AN: 1111774

Other (OTH) AF: 0.0000166 AC: 1 AN: 60362

GnomAD4 genome Cov.: 33

ClinVar

ClinVar submissions

Significance: Uncertain significance

Revision: criteria provided, single submitter

Pathogenic	VUS	Benign	Condition
-	1	-	Autosomal recessive limb-girdle muscular dystrophy type 2J;C1858763:Dilated cardiomyopathy 1G (1)

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
PhyloP100		2.9
Mutation Taster		=1/199	disease causing (fs/PTC)

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: rs778392667; hg19: chr2-179598067;