2-178734925-C-T

Position:

• chr2-178734925-C-T

Variant summary

Our verdict is Likely benign. Variant got -1 ACMG points: 1P and 2B. PP2 BP4_Moderate

The NM_001267550.2(TTN):​c.14999G>A​(p.Arg5000His) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000242 in 1,611,166 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 12/18 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. R5000C) has been classified as Likely benign.

• Frequency:
  • Genomes: 𝑓 0.000053 (0 hom., cov: 33)
  • Exomes 𝑓: 0.000021 (0 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 3.03

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 Likely_benign. 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.
• BP4: Computational evidence support a benign effect (MetaRNN=0.1723578).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTN	NM_001267550.2	c.14999G>A	p.Arg5000His	missense_variant	51/363	ENST00000589042.5

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTN	ENST00000589042.5	c.14999G>A	p.Arg5000His	missense_variant	51/363	5	NM_001267550.2	P1
TTN-AS1	ENST00000659121.1	n.628+296C>T		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes AF: 0.0000526 AC: 8 AN: 152156 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.0000241

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000262

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: 0.0000441

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.0000206 AC: 5 AN: 242268 Hom.: 0 AF XY: 0.0000304 AC XY: 4 AN XY: 131512

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000296

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.0000331

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000276

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000212 AC: 31 AN: 1459010 Hom.: 0 Cov.: 31 AF XY: 0.0000221 AC XY: 16 AN XY: 725586

Gnomad4 AFR exome AF: 0.0000299

Gnomad4 AMR exome AF: 0.0000226

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.0000507

Gnomad4 SAS exome AF: 0.000128

Gnomad4 FIN exome AF: 0.0000188

Gnomad4 NFE exome AF: 0.0000126

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome AF: 0.0000526 AC: 8 AN: 152156 Hom.: 0 Cov.: 33 AF XY: 0.0000673 AC XY: 5 AN XY: 74322

Gnomad4 AFR AF: 0.0000241

Gnomad4 AMR AF: 0.000262

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.0000441

Gnomad4 OTH AF: 0.00

Alfa AF: 0.0000901 Hom.: 0

Bravo AF: 0.0000491

ESP6500AA AF: 0.00 AC: 0

ESP6500EA AF: 0.000122 AC: 1

ExAC AF: 0.0000166 AC: 2

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Athena Diagnostics	Jun 09, 2020	- -
Uncertain significance, criteria provided, single submitter	clinical testing	GeneDx	May 02, 2017	The R3756H variant has not been published as a pathogenic variant, nor has it been reported as a benign variant to our knowledge. The R3756H variant is observed in 1/49074 (0.002%) allele from individuals of European background (Lek et al., 2016; 1000 Genomes Consortium et al., 2015; Exome Variant Server). This variant is a conservative amino acid substitution, which is not likely to impact secondary protein structure as these residues share similar properties. This substitution occurs at a position where amino acids with similar properties to Arginine are tolerated across species. Additionally, the R3756H variant is not located in the A-band nor the M-line region of titin, where the majority of pathogenic truncating variants have been reported. However, in silico analysis predicts this variant is probably damaging to the protein structure/function. -

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

May 11, 2017

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.077
BayesDel_addAF	Benign	-0.17	T
BayesDel_noAF	Benign	-0.37
CADD	Uncertain	24
DANN	Benign	0.96
Eigen	Benign	0.096
Eigen_PC	Uncertain	0.29
FATHMM_MKL	Uncertain	0.92	D
LIST_S2	Benign	0.79	T;T;.;T
M_CAP	Benign	0.012	T
MetaRNN	Benign	0.17	T;T;T;T
MetaSVM	Benign	-1.0	T
MutationTaster	Benign	1.0	D;D;D;N;N;N
PrimateAI	Benign	0.44	T
PROVEAN	Uncertain	-2.5	D;.;.;.
REVEL	Benign	0.18
Sift	Benign	0.090	T;.;.;.
Polyphen		0.066	.;.;B;B
Vest4		0.25
MVP		0.092
MPC		0.11
ClinPred		0.16	T
GERP RS		5.9

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: rs377062348; hg19: chr2-179599652; COSMIC: COSV59987591; COSMIC: COSV59987591;