NM_001267550.2:c.13945A>G

Variant names:

• chr2-178739288-T-C
• rs1060500392
• NM_001267550.2:c.13945A>G

Variant summary

Our verdict is Likely benign. The variant received -2 ACMG points: 0P and 2B. BP4_Moderate

The NM_001267550.2(TTN):​c.13945A>G​(p.Lys4649Glu) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000685 in 1,460,694 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 15/19 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Synonymous variant affecting the same amino acid position (i.e. K4649K) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000068 (0 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 2.31
• Publications: 2 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]

LOC124906101 (HGNC:):

ACMG classification

Our verdict: Likely_benign. The variant received -2 ACMG points.

• BP4: Computational evidence support a benign effect (MetaRNN=0.09834862).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTN	NM_001267550.2	c.13945A>G	p.Lys4649Glu	missense_variant	Exon 48 of 363	ENST00000589042.5	NP_001254479.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.13945A>G	p.Lys4649Glu	missense_variant	Exon 48 of 363	5	NM_001267550.2	ENSP00000467141.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000685 AC: 10 AN: 1460694 Hom.: 0 Cov.: 31 AF XY: 0.00000413 AC XY: 3 AN XY: 726494

African (AFR) AF: 0.00 AC: 0 AN: 33462

American (AMR) AF: 0.00 AC: 0 AN: 44688

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26112

East Asian (EAS) AF: 0.00 AC: 0 AN: 39578

South Asian (SAS) AF: 0.00 AC: 0 AN: 86216

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53340

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5758

European-Non Finnish (NFE) AF: 0.00000810 AC: 9 AN: 1111216

Other (OTH) AF: 0.0000166 AC: 1 AN: 60324

GnomAD4 genome Cov.: 32

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.00000378

EpiCase AF: 0.00

EpiControl AF: 0.0000594

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

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

Dec 05, 2016

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces lysine with glutamic acid at codon 4649 of the TTN protein (p.Lys4649Glu). The lysine residue is weakly conserved and there is a small physicochemical difference between lysine and glutamic acid. This variant is not present in population databases (ExAC no frequency) and has not been reported in the literature in individuals with a TTN-related disease. Algorithms developed to predict the effect of missense changes on protein structure and function are unavailable for the TTN gene. In summary, this variant is a novel missense change with uncertain impact on protein function. It has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.15
BayesDel_addAF	Benign	-0.18	T
BayesDel_noAF	Benign	-0.49
CADD	Benign	21
DANN	Benign	0.95
Eigen	Benign	-0.15
Eigen_PC	Benign	0.023
FATHMM_MKL	Uncertain	0.84	D
LIST_S2	Benign	0.71	T;T;.;T;T;T
M_CAP	Benign	0.013	T
MetaRNN	Benign	0.098	T;T;T;T;T;T
MetaSVM	Benign	-1.0	T
PhyloP100		2.3
PrimateAI	Benign	0.31	T
PROVEAN	Benign	-1.5	N;.;.;N;N;.
REVEL	Benign	0.11
Sift	Benign	0.89	T;.;.;T;T;.
Vest4		0.11
MutPred		0.54		.;.;.;.;Loss of ubiquitination at K4478 (P = 0.0134);.;
MVP		0.17
MPC		0.12
ClinPred		0.33	T
GERP RS		4.7
Mutation Taster		=47/53	disease causing

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: rs1060500392; hg19: chr2-179604015;