2-178585291-G-T

Variant names:

• chr2-178585291-G-T
• rs768345594
• NM_001267550.2:c.64453C>A

Variant summary

Our verdict is Likely benign. The variant received -4 ACMG points: 0P and 4B. BP4_Moderate BP6 BP7

The NM_001267550.2(TTN):​c.64453C>A​(p.Arg21485Arg) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000385 in 1,611,460 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Synonymous variant affecting the same amino acid position (i.e. R21485R) has been classified as Likely benign.

• Frequency:
  • Genomes: 𝑓 0.000026 (0 hom., cov: 32)
  • Exomes 𝑓: 0.000040 (0 hom.)
• Consequence: TTN NM_001267550.2 synonymous
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:3 B:4
• Conservation: PhyloP100: 1.91
• Publications: 3 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: Likely_benign. The variant received -4 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.33).
• BP6: Variant 2-178585291-G-T is Benign according to our data. Variant chr2-178585291-G-T is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 808969.
• BP7: Synonymous conserved (PhyloP=1.91 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

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TTN	NM_001267550.2	MANE Select	c.64453C>A	p.Arg21485Arg	synonymous	Exon 309 of 363	NP_001254479.2	Q8WZ42-12
	TTN	NM_001256850.1		c.59530C>A	p.Arg19844Arg	synonymous	Exon 259 of 313	NP_001243779.1	Q8WZ42-1
	TTN	NM_133378.4		c.56749C>A	p.Arg18917Arg	synonymous	Exon 258 of 312	NP_596869.4	Q8WZ42-11

Ensembl Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TTN	ENST00000589042.5	TSL:5 MANE Select	c.64453C>A	p.Arg21485Arg	synonymous	Exon 309 of 363	ENSP00000467141.1	Q8WZ42-12
	TTN	ENST00000446966.2	TSL:1	c.64297C>A	p.Arg21433Arg	synonymous	Exon 307 of 361	ENSP00000408004.2	A0A1B0GXE3
	TTN	ENST00000436599.2	TSL:1	c.64177C>A	p.Arg21393Arg	synonymous	Exon 307 of 361	ENSP00000405517.2	A0A0C4DG59

Frequencies

GnomAD3 genomes AF: 0.0000263 AC: 4 AN: 151994 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.000779

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: 0.0000688 AC: 17 AN: 246988 AF XY: 0.0000672

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.000952

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000397 AC: 58 AN: 1459348 Hom.: 0 Cov.: 32 AF XY: 0.0000413 AC XY: 30 AN XY: 725798

African (AFR) AF: 0.00 AC: 0 AN: 33286

American (AMR) AF: 0.00 AC: 0 AN: 44452

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26068

East Asian (EAS) AF: 0.00136 AC: 54 AN: 39646

South Asian (SAS) AF: 0.00 AC: 0 AN: 85780

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53356

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5744

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1110734

Other (OTH) AF: 0.0000664 AC: 4 AN: 60282

GnomAD4 genome AF: 0.0000263 AC: 4 AN: 152112 Hom.: 0 Cov.: 32 AF XY: 0.0000403 AC XY: 3 AN XY: 74356

African (AFR) AF: 0.00 AC: 0 AN: 41530

American (AMR) AF: 0.00 AC: 0 AN: 15276

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

East Asian (EAS) AF: 0.000781 AC: 4 AN: 5124

South Asian (SAS) AF: 0.00 AC: 0 AN: 4816

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10618

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

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 67968

Other (OTH) AF: 0.00 AC: 0 AN: 2108

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.0000227

Asia WGS AF: 0.000289 AC: 1 AN: 3478

ClinVar

ClinVar submissions

Significance: Conflicting classifications of pathogenicity

Revision: criteria provided, conflicting classifications

Pathogenic	VUS	Benign	Condition
-	1	-	Autosomal recessive limb-girdle muscular dystrophy type 2J (1)
-	-	1	Autosomal recessive limb-girdle muscular dystrophy type 2J;C1858763:Dilated cardiomyopathy 1G (1)
-	-	1	Cardiovascular phenotype (1)
-	1	-	Dilated cardiomyopathy 1G (1)
-	1	-	Early-onset myopathy with fatal cardiomyopathy (1)
-	-	1	Myopathy, myofibrillar, 9, with early respiratory failure (1)
-	-	1	Tibial muscular dystrophy (1)

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.33
CADD	Benign	1.6
DANN	Benign	0.78
PhyloP100		1.9
Mutation Taster		=51/49	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: rs768345594; hg19: chr2-179450018;