chr2-178720391-A-G

Variant names:

• chr2-178720391-A-G
• rs727505045
• NM_001267550.2:c.23371T>C

Variant summary

Our verdict is Uncertain significance. The variant received 0 ACMG points: 2P and 2B. PM2 BP4_Moderate

The NM_001267550.2(TTN):​c.23371T>C​(p.Phe7791Leu) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,458,944 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 12/19 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Another nucleotide change resulting in the same amino acid substitution has been previously reported as Uncertain significance in ClinVar.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 3.07
• Publications: 0 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: Uncertain_significance. The variant received 0 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.10029858).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTN	NM_001267550.2	c.23371T>C	p.Phe7791Leu	missense_variant	Exon 80 of 363	ENST00000589042.5	NP_001254479.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.23371T>C	p.Phe7791Leu	missense_variant	Exon 80 of 363	5	NM_001267550.2	ENSP00000467141.1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD2 exomes AF: 0.00000405 AC: 1 AN: 246812 AF XY: 0.00

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.0000557

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1458944 Hom.: 0 Cov.: 35 AF XY: 0.00 AC XY: 0 AN XY: 725496

African (AFR) AF: 0.00 AC: 0 AN: 33300

American (AMR) AF: 0.00 AC: 0 AN: 44470

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 25988

East Asian (EAS) AF: 0.0000252 AC: 1 AN: 39678

South Asian (SAS) AF: 0.00 AC: 0 AN: 85826

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53294

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5750

European-Non Finnish (NFE) AF: 9.01e-7 AC: 1 AN: 1110420

Other (OTH) AF: 0.00 AC: 0 AN: 60218

GnomAD4 genome Cov.: 33

ExAC AF: 0.00000828 AC: 1

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not specified Uncertain:1

Mar 18, 2014

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The Phe6547Leu variant in TTN has not been previously reported in individuals wi th cardiomyopathy or in large population studies. Computational prediction tool s and conservation analysis suggest that the Phe6547Leu variant may not impact t he protein, though this information is not predictive enough to rule out pathoge nicity. Additional information is needed to fully assess the clinical significan ce of the Phe6547Leu variant. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.68
BayesDel_addAF	Benign	-0.20	T
BayesDel_noAF	Benign	-0.35
CADD	Benign	22
DANN	Benign	0.96
Eigen	Benign	-0.17
Eigen_PC	Benign	0.098
FATHMM_MKL	Uncertain	0.82	D
LIST_S2	Benign	0.56	T;T;.;T
M_CAP	Benign	0.0097	T
MetaRNN	Benign	0.10	T;T;T;T
MetaSVM	Benign	-1.1	T
PhyloP100		3.1
PrimateAI	Uncertain	0.59	T
PROVEAN	Uncertain	-2.5	D;.;.;.
REVEL	Benign	0.16
Sift	Benign	0.48	T;.;.;.
Polyphen		0.0050	.;.;B;B
Vest4		0.28
MutPred		0.45		.;.;Loss of methylation at K7475 (P = 0.0355);Loss of methylation at K7475 (P = 0.0355);
MVP		0.13
MPC		0.10
ClinPred		0.30	T
GERP RS		5.9
Mutation Taster		=78/22	polymorphism

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: rs727505045; hg19: chr2-179585118;