rs397517650

Positions:

• chr2-178776446-C-A

Variant summary

Our verdict is Likely benign. Variant got -1 ACMG points: 1P and 2B. PP2 BP4_Moderate

The NM_001267550.2(TTN):​c.5418G>T​(p.Leu1806Phe) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000746 in 1,609,010 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 12/18 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., cov: 33)
  • Exomes 𝑓: 0.0000076 (0 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 1.55

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 -1 ACMG points.

• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), TTN. . Gene score misZ -1.1021 (greater than the threshold 3.09). Trascript score misZ 6.9794 (greater than threshold 3.09). GenCC has associacion of gene with dilated cardiomyopathy, tibial muscular dystrophy, early-onset myopathy with fatal cardiomyopathy, autosomal recessive centronuclear myopathy, hypertrophic cardiomyopathy, hypertrophic cardiomyopathy 9, TTN-related myopathy, dilated cardiomyopathy 1G, arrhythmogenic right ventricular cardiomyopathy, myopathy, myofibrillar, 9, with early respiratory failure, familial isolated dilated cardiomyopathy, childhood-onset progressive contractures-limb-girdle weakness-muscle dystrophy syndrome, autosomal recessive limb-girdle muscular dystrophy type 2J.
• BP4: Computational evidence support a benign effect (MetaRNN=0.23180279).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTN	NM_001267550.2	c.5418G>T	p.Leu1806Phe	missense_variant	28/363	ENST00000589042.5	NP_001254479.2
TTN	NM_133379.5	c.5418G>T	p.Leu1806Phe	missense_variant	28/46	ENST00000360870.10	NP_596870.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.5418G>T	p.Leu1806Phe	missense_variant	28/363	5	NM_001267550.2	ENSP00000467141	P1
TTN	ENST00000360870.10	c.5418G>T	p.Leu1806Phe	missense_variant	28/46	5	NM_133379.5	ENSP00000354117
TTN-AS1	ENST00000659121.1	n.3873C>A		non_coding_transcript_exon_variant	12/13

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152226 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.0000241

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.00

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 0.00000755 AC: 11 AN: 1456784 Hom.: 0 Cov.: 33 AF XY: 0.00000690 AC XY: 5 AN XY: 724964

Gnomad4 AFR exome AF: 0.0000299

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: 0.00000899

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152226 Hom.: 0 Cov.: 33 AF XY: 0.0000134 AC XY: 1 AN XY: 74364

Gnomad4 AFR AF: 0.0000241

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Mar 29, 2023	- -
Uncertain significance, criteria provided, single submitter	clinical testing	GeneDx	Jun 16, 2021	Has not been previously published as pathogenic or benign to our knowledge; Not observed at 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; Reported in ClinVar but additional evidence is not available (ClinVar Variant ID# 47176; Landrum et al., 2016) -

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Jan 28, 2013

The Leu1806Phe variant in TTN has not been reported in the literature nor previo usly identified by our laboratory. This variant has also not been identified in large and broad European American and African American populations by the NHLBI Exome Sequencing Project (http://evs.gs.washington.edu/EVS), though it may be co mmon in other populations. Computational analyses (biochemical amino acid proper ties, conservation, AlignGVGD, PolyPhen2, and SIFT) do not provide strong suppor t for or against an impact to the protein. Additional information is needed to f ully assess the clinical significance of this variant. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.25
BayesDel_addAF	Benign	-0.034	T
BayesDel_noAF	Benign	-0.29
CADD	Benign	17
DANN	Benign	0.95
Eigen	Uncertain	0.48
Eigen_PC	Uncertain	0.47
FATHMM_MKL	Uncertain	0.80	D
LIST_S2	Uncertain	0.95	D;D;D;.;D;D;D;D
M_CAP	Benign	0.012	T
MetaRNN	Benign	0.23	T;T;T;T;T;T;T;T
MetaSVM	Benign	-0.57	T
MutationTaster	Benign	0.67	D;N;N;N;N;N;N
PrimateAI	Uncertain	0.76	T
PROVEAN	Uncertain	-2.6	D;D;.;.;D;D;.;D
REVEL	Benign	0.15
Sift	Uncertain	0.017	D;D;.;.;D;D;.;T
Sift4G	Uncertain	0.0030	.;.;.;.;.;.;.;D
Polyphen		1.0, 1.0	.;.;.;D;.;.;D;D
Vest4		0.37
MutPred		0.22		Loss of ubiquitination at K1811 (P = 0.0853);.;Loss of ubiquitination at K1811 (P = 0.0853);Loss of ubiquitination at K1811 (P = 0.0853);.;.;Loss of ubiquitination at K1811 (P = 0.0853);Loss of ubiquitination at K1811 (P = 0.0853);
MVP		0.57
MPC		0.48
ClinPred		0.47	T
GERP RS		4.0

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: rs397517650; hg19: chr2-179641173;