2-178577794-C-G

Variant names:

• chr2-178577794-C-G
• rs764263517
• NM_001267550.2:c.68632G>C

Variant summary

Our verdict is Likely benign. The variant received -1 ACMG points: 0P and 1B. BP4

The NM_001267550.2(TTN):​c.68632G>C​(p.Val22878Leu) variant causes a missense change. In-silico tool predicts a benign outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. V22878M) has been classified as Likely benign.

• Frequency:
  • Genomes: 𝑓 0.000020 (0 hom., cov: 32)
  • Exomes 𝑓: 0.0 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 4.07
• 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]

ENSG00000271011 (HGNC:):

ACMG classification

Our verdict: Likely_benign. The variant received -1 ACMG points.

• BP4: Computational evidence support a benign effect (MetaRNN=0.3386527).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTN	NM_001267550.2	c.68632G>C	p.Val22878Leu	missense_variant	Exon 323 of 363	ENST00000589042.5	NP_001254479.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.68632G>C	p.Val22878Leu	missense_variant	Exon 323 of 363	5	NM_001267550.2	ENSP00000467141.1

Frequencies

GnomAD3 genomes AF: 0.0000198 AC: 3 AN: 151870 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000242

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

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: 0.0000294

Gnomad OTH AF: 0.00

GnomAD4 exome Data not reliable, filtered out with message: AC0;AS_VQSR AF: 0.00 AC: 0 AN: 1460796 Hom.: 0 Cov.: 35 AF XY: 0.00 AC XY: 0 AN XY: 726636

African (AFR) AF: 0.00 AC: 0 AN: 33448

American (AMR) AF: 0.00 AC: 0 AN: 44666

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26100

East Asian (EAS) AF: 0.00 AC: 0 AN: 39584

South Asian (SAS) AF: 0.00 AC: 0 AN: 86136

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53312

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5748

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1111464

Other (OTH) AF: 0.00 AC: 0 AN: 60338

GnomAD4 genome Data not reliable, filtered out with message: AS_VQSR AF: 0.0000198 AC: 3 AN: 151870 Hom.: 0 Cov.: 32 AF XY: 0.0000135 AC XY: 1 AN XY: 74180

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.0000242 AC: 1 AN: 41326

American (AMR) AF: 0.00 AC: 0 AN: 15248

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3464

East Asian (EAS) AF: 0.00 AC: 0 AN: 5138

South Asian (SAS) AF: 0.00 AC: 0 AN: 4830

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10620

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 312

European-Non Finnish (NFE) AF: 0.0000294 AC: 2 AN: 67928

Other (OTH) AF: 0.00 AC: 0 AN: 2092

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5. (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.51
BayesDel_addAF	Benign	-0.0071	T
BayesDel_noAF	Benign	-0.25
CADD	Benign	21
DANN	Benign	0.91
Eigen	Uncertain	0.63
Eigen_PC	Uncertain	0.65
FATHMM_MKL	Uncertain	0.97	D
LIST_S2	Uncertain	0.96	D;D;D;.;D;D;D
M_CAP	Benign	0.049	D
MetaRNN	Benign	0.34	T;T;T;T;T;T;T
MetaSVM	Benign	-0.29	T
MutationAssessor	Uncertain	2.0	.;.;.;M;.;.;M
PhyloP100		4.1
PrimateAI	Uncertain	0.67	T
PROVEAN	Benign	-2.2	N;N;.;.;N;N;.
REVEL	Uncertain	0.29
Sift	Uncertain	0.0080	D;D;.;.;D;D;.
Polyphen		0.98	.;.;.;D;.;.;D
Vest4		0.37
MutPred		0.66		.;.;.;Loss of methylation at K21239 (P = 0.0677);.;.;Loss of methylation at K21239 (P = 0.0677);
MVP		0.51
MPC		0.28
ClinPred		0.45	T
GERP RS		5.7
Mutation Taster		=38/62	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: rs764263517; hg19: chr2-179442521;