chr2-178776102-A-G

Variant names:

• chr2-178776102-A-G
• rs786205318
• NM_001267550.2:c.5762T>C

Variant summary

Our verdict is Likely benign. The variant received -2 ACMG points: 2P and 4B. PM2 BP4_Strong

The NM_001267550.2(TTN):​c.5762T>C​(p.Ile1921Thr) variant causes a missense 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. 16/19 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. I1921V) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 32)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: -0.171
• 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 -2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.050255656).

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.5762T>C	p.Ile1921Thr	missense	Exon 28 of 363	NP_001254479.2
	TTN	NM_001256850.1		c.5762T>C	p.Ile1921Thr	missense	Exon 28 of 313	NP_001243779.1
	TTN	NM_133378.4		c.5762T>C	p.Ile1921Thr	missense	Exon 28 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.5762T>C	p.Ile1921Thr	missense	Exon 28 of 363	ENSP00000467141.1
	TTN	ENST00000446966.2	TSL:1	c.5762T>C	p.Ile1921Thr	missense	Exon 28 of 361	ENSP00000408004.2
	TTN	ENST00000436599.2	TSL:1	c.5486T>C	p.Ile1829Thr	missense	Exon 26 of 361	ENSP00000405517.2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 33

GnomAD4 genome Cov.: 32

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Uncertain:1

Jun 24, 2013

Biesecker Lab/Clinical Genomics Section, National Institutes of Health

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: research

Cardiovascular phenotype Uncertain:1

Jan 25, 2018

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.I1875T variant (also known as c.5624T>C), located in coding exon 26 of the TTN gene, results from a T to C substitution at nucleotide position 5624. The isoleucine at codon 1875 is replaced by threonine, an amino acid with similar properties. This amino acid position is poorly conserved in available vertebrate species. In addition, this alteration is predicted to be tolerated by in silico analysis. Since supporting evidence is limited at this time, the clinical significance of this alterations remains unclear.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.063
BayesDel_addAF	Benign	-0.24	T
BayesDel_noAF	Benign	-0.59
CADD	Benign	7.6
DANN	Benign	0.71
Eigen	Benign	-0.86
Eigen_PC	Benign	-0.81
FATHMM_MKL	Benign	0.021	N
LIST_S2	Benign	0.83	T
M_CAP	Benign	0.017	T
MetaRNN	Benign	0.050	T
MetaSVM	Benign	-0.98	T
PhyloP100		-0.17
PrimateAI	Benign	0.31	T
PROVEAN	Benign	0.65	N
REVEL	Benign	0.14
Sift	Benign	0.68	T
Sift4G	Benign	0.80	T
Polyphen		0.0	B
Vest4		0.26
MutPred		0.42		Gain of disorder (P = 0.0168)
MVP		0.24
MPC		0.11
ClinPred		0.027	T
GERP RS		-3.1
Mutation Taster		=78/22	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: rs786205318; hg19: chr2-179640829;