NM_001267550.2:c.107099A>G

Variant names:

• chr2-178528652-T-C
• rs1060500391
• NM_001267550.2:c.107099A>G

Variant summary

Our verdict is Uncertain significance. The variant received 0 ACMG points: 2P and 2B. PM2 BP4_Moderate

The NM_001267550.2(TTN):​c.107099A>G​(p.Asp35700Gly) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,460,800 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 16/20 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. D35700N) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 2.42
• 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: Uncertain_significance. The variant received 0 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.13963813).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTN	NM_001267550.2	c.107099A>G	p.Asp35700Gly	missense_variant	Exon 360 of 363	ENST00000589042.5	NP_001254479.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.107099A>G	p.Asp35700Gly	missense_variant	Exon 360 of 363	5	NM_001267550.2	ENSP00000467141.1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1460800 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 726586

African (AFR) AF: 0.00 AC: 0 AN: 33472

American (AMR) AF: 0.00 AC: 0 AN: 44574

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26102

East Asian (EAS) AF: 0.00 AC: 0 AN: 39670

South Asian (SAS) AF: 0.00 AC: 0 AN: 86112

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53332

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 0.00000180 AC: 2 AN: 1111430

Other (OTH) AF: 0.00 AC: 0 AN: 60340

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

Nov 12, 2016

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may alter RNA splicing, but this prediction has not been confirmed by published transcriptional studies. In summary, this variant is a novel missense change with uncertain 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. Algorithms developed to predict the effect of missense changes on protein structure and function are unavailable for the TTN gene. This variant is not present in population databases (ExAC no frequency) and has not been reported in the literature in individuals with a TTN-related disease. This sequence change replaces aspartic acid with glycine at codon 35700 of the TTN protein (p.Asp35700Gly). The aspartic acid residue is weakly conserved and there is a moderate physicochemical difference between aspartic acid and glycine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.18
BayesDel_addAF	Benign	-0.10	T
BayesDel_noAF	Benign	-0.39
CADD	Benign	16
DANN	Benign	0.80
Eigen	Benign	-0.29
Eigen_PC	Benign	-0.090
FATHMM_MKL	Uncertain	0.86	D
LIST_S2	Benign	0.77	T;T;T;.;T;T;T
M_CAP	Benign	0.022	T
MetaRNN	Benign	0.14	T;T;T;T;T;T;T
MetaSVM	Benign	-0.96	T
MutationAssessor	Benign	0.12	.;.;.;N;.;.;N
PhyloP100		2.4
PrimateAI	Benign	0.30	T
PROVEAN	Uncertain	-3.7	D;D;.;.;D;D;.
REVEL	Benign	0.17
Sift	Benign	0.44	.;T;.;.;T;T;.
Polyphen		0.0	.;.;.;B;.;.;B
Vest4		0.27
MutPred		0.33		.;.;.;Gain of glycosylation at S34058 (P = 0.0806);.;.;Gain of glycosylation at S34058 (P = 0.0806);
MVP		0.20
MPC		0.11
ClinPred		0.28	T
GERP RS		4.4
Mutation Taster		=84/16	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: rs1060500391; hg19: chr2-179393379;