2-178621704-A-G

Variant names:

• chr2-178621704-A-G
• rs74580375
• NM_001267550.2:c.45120T>C

Variant summary

Our verdict is Benign. The variant received -11 ACMG points: 0P and 11B. BP4_Moderate BP6_Very_Strong BP7

The NM_001267550.2(TTN):​c.45120T>C​(p.Ile15040Ile) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000496 in 1,611,844 control chromosomes in the GnomAD database, including 1 homozygotes. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Likely benign (★★).

• Frequency:
  • Genomes: 𝑓 0.000039 (1 hom., cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: TTN NM_001267550.2 synonymous
• Clinical Significance: Likely benign criteria provided, multiple submitters, no conflicts B:3
• Conservation: PhyloP100: 2.03
• Publications: 8 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 -11 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.46).
• BP6: Variant 2-178621704-A-G is Benign according to our data. Variant chr2-178621704-A-G is described in ClinVar as Likely_benign. ClinVar VariationId is 228095.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• BP7: Synonymous conserved (PhyloP=2.03 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.45120T>C	p.Ile15040Ile	synonymous	Exon 245 of 363	NP_001254479.2
	TTN	NM_001256850.1		c.40197T>C	p.Ile13399Ile	synonymous	Exon 195 of 313	NP_001243779.1
	TTN	NM_133378.4		c.37416T>C	p.Ile12472Ile	synonymous	Exon 194 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.45120T>C	p.Ile15040Ile	synonymous	Exon 245 of 363	ENSP00000467141.1
	TTN	ENST00000446966.2	TSL:1	c.44964T>C	p.Ile14988Ile	synonymous	Exon 243 of 361	ENSP00000408004.2
	TTN	ENST00000436599.2	TSL:1	c.44844T>C	p.Ile14948Ile	synonymous	Exon 243 of 361	ENSP00000405517.2

Frequencies

GnomAD3 genomes AF: 0.0000395 AC: 6 AN: 151886 Hom.: 1 Cov.: 32

Gnomad AFR AF: 0.000145

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.00

Gnomad OTH AF: 0.00

GnomAD2 exomes AF: 0.00000815 AC: 2 AN: 245532 AF XY: 0.00

Gnomad AFR exome AF: 0.000130

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: 0.00000137 AC: 2 AN: 1459840 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 726172

⚠️ 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: 33380

American (AMR) AF: 0.00 AC: 0 AN: 44548

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26078

East Asian (EAS) AF: 0.00 AC: 0 AN: 39440

South Asian (SAS) AF: 0.00 AC: 0 AN: 86130

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53232

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

European-Non Finnish (NFE) AF: 9.00e-7 AC: 1 AN: 1111038

Other (OTH) AF: 0.0000166 AC: 1 AN: 60244

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.00666416), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome AF: 0.0000395 AC: 6 AN: 152004 Hom.: 1 Cov.: 32 AF XY: 0.0000538 AC XY: 4 AN XY: 74292

African (AFR) AF: 0.000144 AC: 6 AN: 41538

American (AMR) AF: 0.00 AC: 0 AN: 15250

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3466

East Asian (EAS) AF: 0.00 AC: 0 AN: 5126

South Asian (SAS) AF: 0.00 AC: 0 AN: 4822

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10608

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 294

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 67878

Other (OTH) AF: 0.00 AC: 0 AN: 2110

Alfa AF: 0.00000202 Hom.: 3

ClinVar

Significance: Likely benign

Submissions summary: Benign:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not specified Benign:1

Apr 01, 2015

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

p.Ile12472Ile in exon 194 of TTN: This variant is not expected to have clinical significance because it does not alter an amino acid residue and is not located within the splice consensus sequence. It has been identified in 2/9614 African c hromosomes by the Exome Aggregation Consortium (ExAC, http://exac.broadinstitute .org; dbSNP rs74580375).

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

Dec 03, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Cardiovascular phenotype Benign:1

Aug 08, 2019

Ambry Genetics

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This alteration is classified as likely benign based on a combination of the following: seen in unaffected individuals, population frequency, intact protein function, lack of segregation with disease, co-occurrence, RNA analysis, in silico models, amino acid conservation, lack of disease association in case-control studies, and/or the mechanism of disease or impacted region is inconsistent with a known cause of pathogenicity.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.46
CADD	Benign	3.6
DANN	Benign	0.80
PhyloP100		2.0
Mutation Taster		=83/17	polymorphism

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.040		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: rs74580375; hg19: chr2-179486431;