2-178709678-G-A

Variant names:

• chr2-178709678-G-A
• rs727505185
• NM_001267550.2:c.28641C>T

Variant summary

Our verdict is Benign. The variant received -11 ACMG points: 2P and 13B. PM2 BP4_Strong BP6_Very_Strong BP7

The NM_001267550.2(TTN):​c.28641C>T​(p.Asn9547Asn) 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 Likely benign (★★).

• Frequency: Genomes: not found (cov: 33)
• Consequence: TTN NM_001267550.2 synonymous
• Clinical Significance: Likely benign criteria provided, multiple submitters, no conflicts B:3
• Conservation: PhyloP100: 0.291
• 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]

LOC124906100 (HGNC:):

ACMG classification

Our verdict: Benign. The variant received -11 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.76).
• BP6: Variant 2-178709678-G-A is Benign according to our data. Variant chr2-178709678-G-A is described in ClinVar as Likely_benign. ClinVar VariationId is 179873.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• BP7: Synonymous conserved (PhyloP=0.291 with no splicing effect.

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

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TTN	NM_001267550.2	MANE Select	c.28641C>T	p.Asn9547Asn	synonymous	Exon 99 of 363	NP_001254479.2
	TTN	NM_001256850.1		c.27690C>T	p.Asn9230Asn	synonymous	Exon 97 of 313	NP_001243779.1
	TTN	NM_133378.4		c.24909C>T	p.Asn8303Asn	synonymous	Exon 96 of 312	NP_596869.4

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TTN	ENST00000589042.5	TSL:5 MANE Select	c.28641C>T	p.Asn9547Asn	synonymous	Exon 99 of 363	ENSP00000467141.1
	TTN	ENST00000446966.2	TSL:1	c.28641C>T	p.Asn9547Asn	synonymous	Exon 99 of 361	ENSP00000408004.2
	TTN	ENST00000436599.2	TSL:1	c.28365C>T	p.Asn9455Asn	synonymous	Exon 97 of 361	ENSP00000405517.2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 33

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.00000756

ClinVar

Significance: Likely benign

Submissions summary: Benign:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not specified Benign:2

Sep 11, 2017

GeneDx

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant is considered likely benign or benign based on one or more of the following criteria: it is a conservative change, it occurs at a poorly conserved position in the protein, it is predicted to be benign by multiple in silico algorithms, and/or has population frequency not consistent with disease.

Jul 11, 2014

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Asn8303Asn in exon 96 of TTN: This variant is not expected to have clinical sign ificance because it does not alter an amino acid residue and is not located with in the splice consensus sequence.

Autosomal recessive limb-girdle muscular dystrophy type 2J;C1858763:Dilated cardiomyopathy 1G Benign:1

Dec 11, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.76
CADD	Benign	0.50
DANN	Benign	0.64
PhyloP100		0.29
Mutation Taster		=98/2	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: rs727505185; hg19: chr2-179574405;