2-178537923-C-T

Variant names:

• chr2-178537923-C-T
• rs727504987
• NM_001267550.2:c.99290-6G>A

Variant summary

Our verdict is Benign. The variant received -12 ACMG points: 0P and 12B. BP4_Strong BP6_Very_Strong

The NM_001267550.2(TTN):​c.99290-6G>A variant causes a splice region, intron change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000298 in 1,442,320 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 3/3 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Likely benign (★★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.000030 (0 hom.)
• Consequence: TTN NM_001267550.2 splice_region, intron
• Scores: Splicing: ADA: 0.00004453
• Clinical Significance: Likely benign criteria provided, multiple submitters, no conflicts B:2
• Conservation: PhyloP100: -0.0550
• 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: Benign. The variant received -12 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.88).
• BP6: Variant 2-178537923-C-T is Benign according to our data. Variant chr2-178537923-C-T is described in ClinVar as Likely_benign. ClinVar VariationId is 413059.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

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.99290-6G>A		splice_region intron	N/A	NP_001254479.2
	TTN	NM_001256850.1		c.94367-6G>A		splice_region intron	N/A	NP_001243779.1
	TTN	NM_133378.4		c.91586-6G>A		splice_region intron	N/A	NP_596869.4

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TTN	ENST00000589042.5	TSL:5 MANE Select	c.99290-6G>A		splice_region intron	N/A	ENSP00000467141.1
	TTN	ENST00000446966.2	TSL:1	c.99134-6G>A		splice_region intron	N/A	ENSP00000408004.2
	TTN	ENST00000436599.2	TSL:1	c.99014-6G>A		splice_region intron	N/A	ENSP00000405517.2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD2 exomes AF: 0.0000667 AC: 15 AN: 224826 AF XY: 0.0000902

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

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: 0.0000298 AC: 43 AN: 1442320 Hom.: 0 Cov.: 32 AF XY: 0.0000377 AC XY: 27 AN XY: 715714

African (AFR) AF: 0.00 AC: 0 AN: 33010

American (AMR) AF: 0.00 AC: 0 AN: 42742

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 25368

East Asian (EAS) AF: 0.00 AC: 0 AN: 39378

South Asian (SAS) AF: 0.000501 AC: 42 AN: 83818

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 51454

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5686

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1101244

Other (OTH) AF: 0.0000168 AC: 1 AN: 59620

GnomAD4 genome Cov.: 33

Alfa AF: 0.00 Hom.: 1

Bravo AF: 0.00000378

ClinVar

Significance: Likely benign

Submissions summary: Benign:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

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

Jan 22, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Cardiomyopathy Benign:1

Jun 19, 2023

CHEO Genetics Diagnostic Laboratory, Children's Hospital of Eastern Ontario

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	-0.88
CADD	Benign	0.15
DANN	Benign	0.59
PhyloP100		-0.055
Mutation Taster		=95/5	polymorphism

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Benign	0.000045
dbscSNV1_RF	Benign	0.030
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: rs727504987; hg19: chr2-179402650;