rs780334981

Positions:

• chr2-178618369-G-A

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 1P and 0B. PP2

The NM_001267550.2(TTN):​c.47089C>T​(p.Arg15697Cys) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000558 in 1,612,340 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: 𝑓 0.000033 (0 hom., cov: 33)
  • Exomes 𝑓: 0.000058 (0 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:4 B:1
• Conservation: PhyloP100: 7.85

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

Verdict is Uncertain_significance. Variant got 1 ACMG points.

• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), TTN. . Gene score misZ -1.1021 (greater than the threshold 3.09). Trascript score misZ 6.9794 (greater than threshold 3.09). GenCC has associacion of gene with dilated cardiomyopathy, tibial muscular dystrophy, early-onset myopathy with fatal cardiomyopathy, autosomal recessive centronuclear myopathy, hypertrophic cardiomyopathy, hypertrophic cardiomyopathy 9, TTN-related myopathy, dilated cardiomyopathy 1G, arrhythmogenic right ventricular cardiomyopathy, myopathy, myofibrillar, 9, with early respiratory failure, familial isolated dilated cardiomyopathy, childhood-onset progressive contractures-limb-girdle weakness-muscle dystrophy syndrome, autosomal recessive limb-girdle muscular dystrophy type 2J.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTN	NM_001267550.2	c.47089C>T	p.Arg15697Cys	missense_variant	252/363	ENST00000589042.5	NP_001254479.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.47089C>T	p.Arg15697Cys	missense_variant	252/363	5	NM_001267550.2	ENSP00000467141	P1
TTN-AS1	ENST00000659121.1	n.502+20688G>A		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes AF: 0.0000329 AC: 5 AN: 151828 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.0000483

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.0000657

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000295

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.0000323 AC: 8 AN: 247718 Hom.: 0 AF XY: 0.0000447 AC XY: 6 AN XY: 134358

Gnomad AFR exome AF: 0.0000647

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.0000563

Gnomad SAS exome AF: 0.0000981

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000268

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000582 AC: 85 AN: 1460512 Hom.: 0 Cov.: 32 AF XY: 0.0000551 AC XY: 40 AN XY: 726562

Gnomad4 AFR exome AF: 0.0000299

Gnomad4 AMR exome AF: 0.0000672

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.0000253

Gnomad4 SAS exome AF: 0.0000580

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000666

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome AF: 0.0000329 AC: 5 AN: 151828 Hom.: 0 Cov.: 33 AF XY: 0.0000270 AC XY: 2 AN XY: 74130

Gnomad4 AFR AF: 0.0000483

Gnomad4 AMR AF: 0.0000657

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.0000295

Gnomad4 OTH AF: 0.00

Alfa AF: 0.0000658 Hom.: 0

Bravo AF: 0.0000340

TwinsUK AF: 0.000270 AC: 1

ALSPAC AF: 0.00 AC: 0

ExAC AF: 0.0000248 AC: 3

EpiCase AF: 0.0000546

EpiControl AF: 0.00

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:4 Benign:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Uncertain:2 Benign:1

Likely benign, criteria provided, single submitter	clinical testing	GeneDx	Mar 16, 2020	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Oct 17, 2017	- -
Uncertain significance, criteria provided, single submitter	research	Biesecker Lab/Clinical Genomics Section, National Institutes of Health	Jun 24, 2013	- -

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

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Oct 12, 2017

- -

Cardiovascular phenotype Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Sep 20, 2019

The p.R6632C variant (also known as c.19894C>T), located in coding exon 79 of the TTN gene, results from a C to T substitution at nucleotide position 19894. The arginine at codon 6632 is replaced by cysteine, an amino acid with highly dissimilar properties. This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be tolerated by in silico analysis. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.65
BayesDel_addAF	Benign	-0.10	T
BayesDel_noAF	Benign	-0.18
CADD	Uncertain	25
DANN	Benign	0.93
Eigen	Pathogenic	0.86
Eigen_PC	Pathogenic	0.85
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Pathogenic	0.97	D;D;D;.;D;D;D
M_CAP	Benign	0.024	T
MetaRNN	Uncertain	0.59	D;D;D;D;D;D;D
MetaSVM	Benign	-0.30	T
MutationAssessor	Uncertain	2.1	.;.;.;M;.;.;M
MutationTaster	Benign	1.0	D;D;D;D;D;D
PrimateAI	Uncertain	0.76	T
PROVEAN	Pathogenic	-6.0	D;D;.;.;D;D;.
REVEL	Uncertain	0.46
Sift	Benign	0.062	T;T;.;.;T;T;.
Polyphen		1.0	.;.;.;D;.;.;D
Vest4		0.58
MutPred		0.73		.;.;.;Loss of MoRF binding (P = 0.0078);.;.;Loss of MoRF binding (P = 0.0078);
MVP		0.53
MPC		0.54
ClinPred		0.36	T
GERP RS		5.8

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		Details are displayed if max score is > 0.2

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

Publications

LitVar

Other links and lift over

dbSNP: rs780334981; hg19: chr2-179483096;