2-178604002-C-A

Variant names:

• chr2-178604002-C-A
• rs116142642
• NM_001267550.2:c.54685G>T

Variant summary

Our verdict is Likely benign. The variant received -2 ACMG points: 2P and 4B. PM2 BP4_Strong

The NM_001267550.2(TTN):​c.54685G>T​(p.Val18229Leu) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000342 in 1,460,836 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 17/20 in silico tools predict 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. V18229M) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000034 (0 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 0.984
• Publications: 5 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]

ACMG classification

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

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.057883263).

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_001267550.2. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TTN	NM_001267550.2	MANE Select	c.54685G>T	p.Val18229Leu	missense	Exon 282 of 363	NP_001254479.2	Q8WZ42-12
	TTN	NM_001256850.1		c.49762G>T	p.Val16588Leu	missense	Exon 232 of 313	NP_001243779.1	Q8WZ42-1
	TTN	NM_133378.4		c.46981G>T	p.Val15661Leu	missense	Exon 231 of 312	NP_596869.4	Q8WZ42-11

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TTN	ENST00000589042.5	TSL:5 MANE Select	c.54685G>T	p.Val18229Leu	missense	Exon 282 of 363	ENSP00000467141.1	Q8WZ42-12
	TTN	ENST00000446966.2	TSL:1	c.54529G>T	p.Val18177Leu	missense	Exon 280 of 361	ENSP00000408004.2	A0A1B0GXE3
	TTN	ENST00000436599.2	TSL:1	c.54409G>T	p.Val18137Leu	missense	Exon 280 of 361	ENSP00000405517.2	A0A0C4DG59

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD2 exomes AF: 0.0000201 AC: 5 AN: 248574 AF XY: 0.0000148

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.000145

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000342 AC: 5 AN: 1460836 Hom.: 0 Cov.: 31 AF XY: 0.00000275 AC XY: 2 AN XY: 726710

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

African (AFR) AF: 0.00 AC: 0 AN: 33414

American (AMR) AF: 0.000112 AC: 5 AN: 44706

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26108

East Asian (EAS) AF: 0.00 AC: 0 AN: 39668

South Asian (SAS) AF: 0.00 AC: 0 AN: 86204

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53400

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5754

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1111262

Other (OTH) AF: 0.00 AC: 0 AN: 60320

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.00000494837), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 32

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.00000378

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.16
BayesDel_addAF	Benign	-0.35	T
BayesDel_noAF	Benign	-0.48
CADD	Benign	10
DANN	Benign	0.90
Eigen	Benign	-0.53
Eigen_PC	Benign	-0.30
FATHMM_MKL	Benign	0.51	D
LIST_S2	Benign	0.82	T
M_CAP	Benign	0.0079	T
MetaRNN	Benign	0.058	T
MetaSVM	Benign	-1.1	T
MutationAssessor	Benign	-0.61	N
PhyloP100		0.98
PrimateAI	Benign	0.38	T
PROVEAN	Benign	-1.2	N
REVEL	Benign	0.11
Sift	Benign	0.50	T
Polyphen		0.0	B
Vest4		0.16
MutPred		0.60		Loss of MoRF binding (P = 0.0957)
MVP		0.19
MPC		0.083
ClinPred		0.059	T
GERP RS		3.1
Mutation Taster		=89/11	polymorphism

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.030		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: rs116142642; hg19: chr2-179468729;