rs1367949983

Positions:

• chr2-178749898-C-T

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 0P and 2B. BP4_Moderate

The NM_133379.5(TTN):​c.12502G>A​(p.Ala4168Thr) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000116 in 1,461,080 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 12/15 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.000012 (0 hom.)
• Consequence: TTN NM_133379.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 0.720

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 Likely_benign. Variant got -2 ACMG points.

• BP4: Computational evidence support a benign effect (MetaRNN=0.07203406).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTN	NM_133379.5	c.12502G>A	p.Ala4168Thr	missense_variant	46/46	ENST00000360870.10
TTN	NM_001267550.2	c.11311+3226G>A		intron_variant		ENST00000589042.5

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTN	ENST00000360870.10	c.12502G>A	p.Ala4168Thr	missense_variant	46/46	5	NM_133379.5
TTN	ENST00000589042.5	c.11311+3226G>A		intron_variant		5	NM_001267550.2	P1
TTN-AS1	ENST00000659121.1	n.1224-6368C>T		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000402 AC: 1 AN: 248948 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 134848

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 SAS 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: 0.0000116 AC: 17 AN: 1461080 Hom.: 0 Cov.: 36 AF XY: 0.00000963 AC XY: 7 AN XY: 726842

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000153

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Jun 21, 2016

The p.Ala4168Thr variant in TTN has not been reported in individuals with cardio myopathy or in large population studies. Computational prediction tools and cons ervation analysis are limited or unavailable for this variant. In summary, the c linical significance of the p.Ala4168Thr variant is uncertain. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Benign	-0.22	T
BayesDel_noAF	Benign	-0.56
CADD	Benign	13
DANN	Uncertain	0.99
Eigen	Benign	-0.76
Eigen_PC	Benign	-0.61
FATHMM_MKL	Benign	0.0083	N
LIST_S2	Benign	0.45	T
M_CAP	Benign	0.0091	T
MetaRNN	Benign	0.072	T
MetaSVM	Benign	-0.99	T
MutationTaster	Benign	1.0	N;N;N;N;N;N;N
PROVEAN	Benign	0.28	N
REVEL	Benign	0.065
Sift	Benign	0.32	T
Sift4G	Benign	0.72	T
Polyphen		0.0010	B
Vest4		0.14
MutPred		0.48		Gain of phosphorylation at A4168 (P = 0.0126);
MVP		0.47
ClinPred		0.062	T
GERP RS		2.6

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

Publications

LitVar

Other links and lift over

dbSNP: rs1367949983; hg19: chr2-179614625;