rs746830456

chr2-178725599-C-Gchr2-178725599-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 3P and 2B. PM2 PP2 BP4_Moderate

The NM_001267550.2(TTN):c.20605G>C(p.Glu6869Gln) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000686 in 1,457,944 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 14/18 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. E6869K) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 2.17

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]

(HGNC:):

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.

• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant where missense usually causes diseases, TTN
• BP4: Computational evidence support a benign effect (MetaRNN=0.22796473).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTN	NM_001267550.2	c.20605G>C	p.Glu6869Gln	missense_variant	71/363	ENST00000589042.5

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTN	ENST00000589042.5	c.20605G>C	p.Glu6869Gln	missense_variant	71/363	5	NM_001267550.2	P1
	ENST00000590024.1	n.2143C>G		non_coding_transcript_exon_variant	1/1
TTN-AS1	ENST00000659121.1	n.503-8905C>G		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 6.86e-7 AC: 1 AN: 1457944 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 724930

Gnomad4 AFR exome AF: 0.0000300

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Cardiovascular phenotype Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Jul 31, 2013

The p.E5625Q variant (also known as c.16873G>C) is located in coding exon 67 of the TTNgene. This alteration results from a G to C substitution at nucleotide position 16873. The glutamic acid at codon 5625 is replaced by glutamine, an amino acid with highly similar properties.This variant was not reported in population-based cohorts in the following databases: Database of Single Nucleotide Polymorphisms (dbSNP), the 1000 Genomes Project and the NHLBI Exome Sequencing Project (ESP). In the ESP, this variant was not observed in 5962 samples (11924 alleles) with coverage at this position. Based on protein sequence alignment, this amino acid positionis not well conserved in available vertebrate species, with glutamine as the reference amino acid in two species, including chimp. In addition, this alteration is predicted to be benign by PolyPhen analysis.Since supporting evidence is limited at this time, the clinical significance of this variant remains unclear.​ -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.091
BayesDel_addAF	Benign	-0.30	T
BayesDel_noAF	Benign	-0.67
Cadd	Benign	18
Dann	Benign	0.90
Eigen	Benign	-0.31
Eigen_PC	Benign	-0.15
FATHMM_MKL	Uncertain	0.89	D
LIST_S2	Benign	0.64	T;T;.;T
M_CAP	Benign	0.017	T
MetaRNN	Benign	0.23	T;T;T;T
MetaSVM	Benign	-1.0	T
MutationTaster	Benign	1.0	D;D;D;N;N;N
PrimateAI	Benign	0.41	T
PROVEAN	Benign	-1.3	N;.;.;.
REVEL	Benign	0.079
Sift	Benign	0.20	T;.;.;.
Polyphen		0.099	.;.;B;B
Vest4		0.12
MutPred		0.45		.;.;Loss of loop (P = 0.1242);Loss of loop (P = 0.1242);
MVP		0.085
MPC		0.094
ClinPred		0.098	T
GERP RS		5.0

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

Publications

LitVar

Other links and lift over

dbSNP: rs746830456; hg19: chr2-179590326;