rs138060032

chr2-178799566-G-A

Variant summary

Our verdict is Uncertain significance. Variant got 0 ACMG points: 1P and 1B. PP2 BP6

The NM_001267550.2(TTN):c.835C>T(p.Arg279Trp) variant causes a missense change. The variant allele was found at a frequency of 0.000397 in 1,614,026 control chromosomes in the GnomAD database, including 1 homozygotes. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Synonymous variant affecting the same amino acid position (i.e. R279R) has been classified as Likely benign.

• Frequency:
  • Genomes: 𝑓 0.00028 (0 hom., cov: 32)
  • Exomes 𝑓: 0.00041 (1 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:16 B:3 O:1
• Conservation: PhyloP100: 6.39

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]

ACMG classification

Verdict is Uncertain_significance. Variant got 0 ACMG points.

• PP2: Missense variant where missense usually causes diseases, TTN
• BP6: Variant 2-178799566-G-A is Benign according to our data. Variant chr2-178799566-G-A is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 12659.We mark this variant Likely_benign, oryginal submissions are: {not_provided=1, Uncertain_significance=11, Likely_benign=3}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTN	NM_001267550.2	c.835C>T	p.Arg279Trp	missense_variant	6/363	ENST00000589042.5
TTN	NM_133379.5	c.835C>T	p.Arg279Trp	missense_variant	6/46	ENST00000360870.10

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTN	ENST00000589042.5	c.835C>T	p.Arg279Trp	missense_variant	6/363	5	NM_001267550.2	P1
TTN	ENST00000360870.10	c.835C>T	p.Arg279Trp	missense_variant	6/46	5	NM_133379.5

Frequencies

GnomAD3 genomes AF: 0.000276 AC: 42 AN: 152176 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000965

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000131

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: 0.000514

Gnomad OTH AF: 0.000478

GnomAD3 exomes AF: 0.000187 AC: 47 AN: 251394 Hom.: 0 AF XY: 0.000162 AC XY: 22 AN XY: 135872

Gnomad AFR exome AF: 0.0000615

Gnomad AMR exome AF: 0.0000867

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: 0.000369

Gnomad OTH exome AF: 0.000163

GnomAD4 exome AF: 0.000409 AC: 598 AN: 1461850 Hom.: 1 Cov.: 31 AF XY: 0.000375 AC XY: 273 AN XY: 727224

Gnomad4 AFR exome AF: 0.0000597

Gnomad4 AMR exome AF: 0.0000671

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.0000562

Gnomad4 NFE exome AF: 0.000518

Gnomad4 OTH exome AF: 0.000232

GnomAD4 genome AF: 0.000276 AC: 42 AN: 152176 Hom.: 0 Cov.: 32 AF XY: 0.000215 AC XY: 16 AN XY: 74342

Gnomad4 AFR AF: 0.0000965

Gnomad4 AMR AF: 0.000131

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.000514

Gnomad4 OTH AF: 0.000478

Alfa AF: 0.000416 Hom.: 0

Bravo AF: 0.000287

TwinsUK AF: 0.00135 AC: 5

ALSPAC AF: 0.000259 AC: 1

ESP6500AA AF: 0.00 AC: 0

ESP6500EA AF: 0.000116 AC: 1

ExAC AF: 0.000132 AC: 16

EpiCase AF: 0.000600

EpiControl AF: 0.000119

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:16 Benign:3 Other:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Uncertain:9 Other:1

Uncertain significance, criteria provided, single submitter	clinical testing	Athena Diagnostics	Sep 14, 2018	- -
Uncertain significance, no assertion criteria provided	clinical testing	Clinical Genetics, Academic Medical Center	-	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Oct 12, 2022	- -
Uncertain significance, criteria provided, single submitter	research	Biesecker Lab/Clinical Genomics Section, National Institutes of Health	Jun 24, 2013	- -
not provided, no classification provided	clinical testing	GeneDx	Sep 04, 2014	- -
Uncertain significance, no assertion criteria provided	clinical testing	Laboratory of Diagnostic Genome Analysis, Leiden University Medical Center (LUMC)	-	- -
Uncertain significance, no assertion criteria provided	clinical testing	Diagnostic Laboratory, Department of Genetics, University Medical Center Groningen	-	- -
Uncertain significance, no assertion criteria provided	clinical testing	Clinical Genetics DNA and cytogenetics Diagnostics Lab, Erasmus MC, Erasmus Medical Center	-	- -
Uncertain significance, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Apr 01, 2017	- -
Uncertain significance, no assertion criteria provided	clinical testing	Joint Genome Diagnostic Labs from Nijmegen and Maastricht, Radboudumc and MUMC+	-	- -

Myopathy, myofibrillar, 9, with early respiratory failure Pathogenic:1 Uncertain:1

Pathogenic, no assertion criteria provided	literature only	OMIM	Jun 10, 2005	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Illumina Laboratory Services, Illumina	Apr 27, 2017	This variant was observed as part of a predisposition screen in an ostensibly healthy population. A literature search was performed for the gene, cDNA change, and amino acid change (where applicable). Publications were found based on this search. However, the evidence from the literature, in combination with allele frequency data from public databases where available, was not sufficient to rule this variant in or out of causing disease. Therefore, this variant is classified as a variant of unknown significance. -

not specified Benign:2

Likely benign, criteria provided, single submitter	clinical testing	Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine	Apr 09, 2018	proposed classification - variant undergoing re-assessment, contact laboratory -
Likely benign, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Jun 19, 2023	Variant summary: TTN c.835C>T (p.Arg279Trp) results in a non-conservative amino acid change located in the Z-disk region of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 0.00019 in 282792 control chromosomes, predominantly at a frequency of 0.00036 within the Non-Finnish European subpopulation in the gnomAD database. This frequency is approximately equal to the estimated maximal expected allele frequency for a pathogenic variant in TTN causing Dilated Cardiomyopathy (0.00039), suggesting that the variant is a benign polymorphism found primarily in populations of Non-Finnish European origin. c.835C>T has been reported in the literature in multiple individuals affected with TTN-related conditions without strong evidence for causality (e.g., Lange_2005, Campuzan_2015, Sanchez_2016, van Spaendonck-Zwart_2014). At-least two co-occurrences with other pathogenic variant(s) have been reported in cis with this variant (TTN c.87491C>T, p.Pro29164Leu, Lange_2005; c.69086_69095del10, p.Arg23029ThrfsX9, van Spaendonck-Zwart_2014), providing supporting evidence for a benign role. Two publications report experimental evidence evaluating an impact on protein function, demonstrating reduced binding to nbd1 in mutant cells (Lange_2005, Chaveau_2014). However, neither study provides quantitative data indicating the strength of the effect. The following publications have been ascertained in the context of this evaluation (PMID: 26516846, 24105469, 24569025, 24578547, 27930701, 20708934, 24558114, 15802564, 24271327, 24231549). Eight submitters have cited clinical-significance assessments for this variant to ClinVar after 2014. Six submitters classified the variant as a variant of uncertain significance, and two classified it as likely benign. Based on the evidence outlined above, the variant was classified as likely benign. -

Autosomal recessive limb-girdle muscular dystrophy type 2J Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Apr 27, 2017

This variant was observed as part of a predisposition screen in an ostensibly healthy population. A literature search was performed for the gene, cDNA change, and amino acid change (where applicable). No publications were found based on this search. Allele frequency data from public databases did not allow this variant to be ruled in or out of causing disease. Therefore, this variant is classified as a variant of unknown significance. -

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

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

May 08, 2017

- -

Dilated cardiomyopathy 1G Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Apr 27, 2017

This variant was observed as part of a predisposition screen in an ostensibly healthy population. A literature search was performed for the gene, cDNA change, and amino acid change (where applicable). No publications were found based on this search. Allele frequency data from public databases did not allow this variant to be ruled in or out of causing disease. Therefore, this variant is classified as a variant of unknown significance. -

Early-onset myopathy with fatal cardiomyopathy Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Apr 27, 2017

This variant was observed as part of a predisposition screen in an ostensibly healthy population. A literature search was performed for the gene, cDNA change, and amino acid change (where applicable). No publications were found based on this search. Allele frequency data from public databases did not allow this variant to be ruled in or out of causing disease. Therefore, this variant is classified as a variant of unknown significance. -

Tibial muscular dystrophy Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Apr 27, 2017

This variant was observed as part of a predisposition screen in an ostensibly healthy population. A literature search was performed for the gene, cDNA change, and amino acid change (where applicable). No publications were found based on this search. Allele frequency data from public databases did not allow this variant to be ruled in or out of causing disease. Therefore, this variant is classified as a variant of unknown significance. -

Cardiovascular phenotype Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Nov 13, 2018

The p.R279W variant (also known as c.835C>T), located in coding exon 5 of the TTN gene, results from a C to T substitution at nucleotide position 835. The arginine at codon 279 is replaced by tryptophan, an amino acid with dissimilar properties. This variant was reported in cis with a truncating TTN alteration in a family with both dilated cardiomyopathy and peripartum cardiomyopathy (van Spaendonck-Zwarts KY et al. Eur Heart J. 2014;35:2165-73). This alteration has also been reported as a secondary cardiac variant in an exome cohort, and was detected in a sudden unexplained death case with variants in other cardiac-related genes (Ng D et al. Circ Cardiovasc Genet. 2013;6:337-46; Sanchez O et al. PLoS ONE. 2016;11(12):e0167358). This amino acid position is highly conserved in available vertebrate species. In addition, the in silico prediction for this alteration is inconclusive. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Cardiomyopathy Benign:1

Likely benign, criteria provided, single submitter

clinical testing

CHEO Genetics Diagnostic Laboratory, Children's Hospital of Eastern Ontario

Dec 10, 2020

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.68
BayesDel_addAF	Benign	-0.11	T
BayesDel_noAF	Uncertain	0.030
Cadd	Uncertain	24
Dann	Uncertain	1.0
Eigen	Uncertain	0.66
Eigen_PC	Uncertain	0.63
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.97	D;D;D;.;D;D;D;D
M_CAP	Benign	0.053	D
MetaRNN	Uncertain	0.48	T;T;T;T;T;T;T;T
MetaSVM	Uncertain	0.25	D
MutationTaster	Benign	0.99	A;A;A;A;A;A;A
PrimateAI	Uncertain	0.69	T
PROVEAN	Pathogenic	-4.9	D;D;.;.;D;D;.;D
REVEL	Uncertain	0.60
Sift	Pathogenic	0.0	D;D;.;.;D;D;.;D
Polyphen		1.0	.;.;.;D;.;.;D;D
Vest4		0.43
MVP		0.56
MPC		0.47
ClinPred		0.77	D
GERP RS		4.8

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: rs138060032; hg19: chr2-179664293; COSMIC: COSV59876236; COSMIC: COSV59876236;