2-178576594-T-G

Variant names:

• chr2-178576594-T-G
• rs72646884
• NM_001267550.2:c.69650A>C

Variant summary

Our verdict is Likely benign. The variant received -1 ACMG points: 0P and 1B. BP4

The NM_001267550.2(TTN):​c.69650A>C​(p.Glu23217Ala) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000684 in 1,461,394 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 Uncertain significance (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000068 (0 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 7.97
• 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: Likely_benign. The variant received -1 ACMG points.

• BP4: Computational evidence support a benign effect (MetaRNN=0.40890077).

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.69650A>C	p.Glu23217Ala	missense	Exon 325 of 363	NP_001254479.2
	TTN	NM_001256850.1		c.64727A>C	p.Glu21576Ala	missense	Exon 275 of 313	NP_001243779.1
	TTN	NM_133378.4		c.61946A>C	p.Glu20649Ala	missense	Exon 274 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.69650A>C	p.Glu23217Ala	missense	Exon 325 of 363	ENSP00000467141.1
	TTN	ENST00000446966.2	TSL:1	c.69494A>C	p.Glu23165Ala	missense	Exon 323 of 361	ENSP00000408004.2
	TTN	ENST00000436599.2	TSL:1	c.69374A>C	p.Glu23125Ala	missense	Exon 323 of 361	ENSP00000405517.2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD2 exomes AF: 0.00000403 AC: 1 AN: 248384 AF XY: 0.00000742

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: 0.00000891

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000684 AC: 10 AN: 1461394 Hom.: 0 Cov.: 35 AF XY: 0.0000110 AC XY: 8 AN XY: 726988

African (AFR) AF: 0.00 AC: 0 AN: 33450

American (AMR) AF: 0.00 AC: 0 AN: 44716

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26124

East Asian (EAS) AF: 0.00 AC: 0 AN: 39678

South Asian (SAS) AF: 0.00 AC: 0 AN: 86242

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53398

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5764

European-Non Finnish (NFE) AF: 0.00000810 AC: 9 AN: 1111668

Other (OTH) AF: 0.0000166 AC: 1 AN: 60354

GnomAD4 genome Cov.: 32

Alfa AF: 0.0000826 Hom.: 0

Bravo AF: 0.0000113

EpiCase AF: 0.00

EpiControl AF: 0.0000593

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Uncertain:3

Apr 12, 2021

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Not observed at a significant frequency in large population cohorts (Lek et al., 2016); Missense variant in a gene in which most reported pathogenic variants are truncating/loss-of-function; Has not been previously published as pathogenic or benign to our knowledge

Jul 28, 2020

Revvity Omics, Revvity

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Jun 24, 2013

Biesecker Lab/Clinical Genomics Section, National Institutes of Health

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: research

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.36
BayesDel_addAF	Uncertain	0.048	T
BayesDel_noAF	Benign	-0.17
CADD	Benign	21
DANN	Benign	0.93
Eigen	Pathogenic	0.73
Eigen_PC	Pathogenic	0.73
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.97	D
M_CAP	Benign	0.025	T
MetaRNN	Benign	0.41	T
MetaSVM	Benign	-0.45	T
MutationAssessor	Uncertain	2.5	M
PhyloP100		8.0
PrimateAI	Uncertain	0.67	T
PROVEAN	Pathogenic	-4.7	D
REVEL	Uncertain	0.39
Sift	Uncertain	0.012	D
Polyphen		1.0	D
Vest4		0.55
MVP		0.34
MPC		0.48
ClinPred		0.38	T
GERP RS		5.7
Mutation Taster		=59/41	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: rs72646884; hg19: chr2-179441321;