rs1553479315

Variant names:

• chr2-178528426-A-G
• rs1553479315
• NM_001267550.2:c.107225T>C

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 2P and 0B. PM2

The NM_001267550.2(TTN):​c.107225T>C​(p.Ile35742Thr) variant causes a missense, splice region change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. 3/3 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 33)
• Consequence: TTN NM_001267550.2 missense, splice_region
• Scores: Splicing: ADA: 0.07283
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 9.02

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

Verdict is Uncertain_significance. Variant got 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTN	NM_001267550.2	c.107225T>C	p.Ile35742Thr	missense_variant, splice_region_variant	Exon 361 of 363	ENST00000589042.5	NP_001254479.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.107225T>C	p.Ile35742Thr	missense_variant, splice_region_variant	Exon 361 of 363	5	NM_001267550.2	ENSP00000467141.1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

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

Dec 11, 2017

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

In summary, this variant is a novel missense change with unknown impact on protein function. Missense variants in this region of the TTN gene are typically not causative for cardiac disease, but may be relevant for neuromuscular disorders. However, the available evidence is currently insufficient to determine this variant’s role in disease. Therefore, it has been classified as a Variant of Uncertain Significance This variant has not been reported in the literature in individuals with TTN-related disease. This variant is not present in population databases (ExAC no frequency). This sequence change replaces isoleucine with threonine at codon 35742 of the TTN protein (p.Ile35742Thr). The isoleucine residue is highly conserved and there is a moderate physicochemical difference between isoleucine and threonine. This variant identified in the TTN gene is located in the M band of the resulting protein (PMID: 25589632). It is unclear how this variant impacts the function of this protein. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.74
BayesDel_addAF	Uncertain	0.063	T
BayesDel_noAF	Benign	-0.15
CADD	Benign	20
DANN	Benign	0.76
Eigen	Pathogenic	0.69
Eigen_PC	Uncertain	0.65
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.89	D;D;D;.;D;D;D
M_CAP	Uncertain	0.12	D
MetaRNN	Uncertain	0.44	T;T;T;T;T;T;T
MetaSVM	Uncertain	0.12	D
MutationAssessor	Uncertain	2.6	.;.;.;M;.;.;M
PrimateAI	Benign	0.47	T
PROVEAN	Uncertain	-3.2	D;D;.;.;D;D;.
REVEL	Uncertain	0.57
Sift	Uncertain	0.0030	.;D;.;.;D;D;.
Polyphen		0.94	.;.;.;P;.;.;P
Vest4		0.32
MutPred		0.69		.;.;.;Gain of disorder (P = 0.0411);.;.;Gain of disorder (P = 0.0411);
MVP		0.74
MPC		0.34
ClinPred		0.60	D
GERP RS		5.3

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Benign	0.073
dbscSNV1_RF	Benign	0.26
SpliceAI score (max)		0.020		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs1553479315; hg19: chr2-179393153;