chr2-178733828-C-A

Variant names:

• chr2-178733828-C-A
• rs779159076
• NM_001267550.2:c.15561G>T

Variant summary

Our verdict is Benign. Variant got -11 ACMG points: 2P and 13B. PM2 BP4_Strong BP6_Very_Strong BP7

The NM_001267550.2(TTN):​c.15561G>T​(p.Leu5187Leu) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Benign (★★). Synonymous variant affecting the same amino acid position (i.e. L5187L) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 33)
• Consequence: TTN NM_001267550.2 synonymous
• Clinical Significance: Benign criteria provided, multiple submitters, no conflicts B:8
• Conservation: PhyloP100: -0.129

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 Benign. Variant got -11 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.57).
• BP6: Variant 2-178733828-C-A is Benign according to our data. Variant chr2-178733828-C-A is described in ClinVar as [Benign]. Clinvar id is 262320.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• BP7: Synonymous conserved (PhyloP=-0.129 with no splicing effect.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTN	NM_001267550.2	c.15561G>T	p.Leu5187Leu	synonymous_variant	Exon 53 of 363	ENST00000589042.5	NP_001254479.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.15561G>T	p.Leu5187Leu	synonymous_variant	Exon 53 of 363	5	NM_001267550.2	ENSP00000467141.1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 36

GnomAD4 genome Cov.: 33

ClinVar

Significance: Benign

Submissions summary: Benign:8

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Autosomal recessive limb-girdle muscular dystrophy type 2J Benign:2

Aug 01, 2017

Phosphorus, Inc.

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Sep 10, 2021

Genome-Nilou Lab

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Tibial muscular dystrophy Benign:2

Aug 01, 2017

Phosphorus, Inc.

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Sep 10, 2021

Genome-Nilou Lab

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

not specified Benign:1

-

PreventionGenetics, part of Exact Sciences

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Dilated cardiomyopathy 1G Benign:1

Aug 01, 2017

Phosphorus, Inc.

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Early-onset myopathy with fatal cardiomyopathy Benign:1

Sep 10, 2021

Genome-Nilou Lab

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Myopathy, myofibrillar, 9, with early respiratory failure Benign:1

Sep 10, 2021

Genome-Nilou Lab

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.57
CADD	Benign	1.0
DANN	Benign	0.66

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

Publications

LitVar

Other links and lift over

dbSNP: rs779159076; hg19: chr2-179598555;