2-178636754-T-C

Position:

• chr2-178636754-T-C

Variant summary

Our verdict is Likely benign. Variant got -4 ACMG points: 1P and 5B. PP2 BP4_Strong BP6

The NM_001267550.2(TTN):​c.40973A>G​(p.Lys13658Arg) variant causes a missense change. The variant allele was found at a frequency of 0.000145 in 1,609,074 control chromosomes in the GnomAD database, including 1 homozygotes. In-silico tool predicts a benign outcome for this variant. 13/19 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Synonymous variant affecting the same amino acid position (i.e. K13658K) has been classified as Likely benign.

• Frequency:
  • Genomes: 𝑓 0.00016 (0 hom., cov: 32)
  • Exomes 𝑓: 0.00014 (1 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:8 B:4
• Conservation: PhyloP100: 3.86

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 -4 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=0.06652439).
• BP6: Variant 2-178636754-T-C is Benign according to our data. Variant chr2-178636754-T-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 178220.We mark this variant Likely_benign, oryginal submissions are: {Likely_benign=2, Uncertain_significance=8, Benign=2}. Variant chr2-178636754-T-C is described in Lovd as [Likely_benign].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTN	NM_001267550.2	c.40973A>G	p.Lys13658Arg	missense_variant	225/363	ENST00000589042.5

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTN	ENST00000589042.5	c.40973A>G	p.Lys13658Arg	missense_variant	225/363	5	NM_001267550.2	P1
TTN-AS1	ENST00000659121.1	n.502+39073T>C		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes AF: 0.000158 AC: 24 AN: 152068 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000724

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000197

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.000415

Gnomad FIN AF: 0.0000942

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.000221

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.000162 AC: 40 AN: 246562 Hom.: 0 AF XY: 0.000202 AC XY: 27 AN XY: 133780

Gnomad AFR exome AF: 0.0000648

Gnomad AMR exome AF: 0.0000880

Gnomad ASJ exome AF: 0.000101

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.000299

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.000223

Gnomad OTH exome AF: 0.000168

GnomAD4 exome AF: 0.000144 AC: 210 AN: 1456888 Hom.: 1 Cov.: 32 AF XY: 0.000177 AC XY: 128 AN XY: 724118

Gnomad4 AFR exome AF: 0.0000301

Gnomad4 AMR exome AF: 0.000180

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.000372

Gnomad4 FIN exome AF: 0.0000750

Gnomad4 NFE exome AF: 0.000119

Gnomad4 OTH exome AF: 0.000299

GnomAD4 genome AF: 0.000158 AC: 24 AN: 152186 Hom.: 0 Cov.: 32 AF XY: 0.000175 AC XY: 13 AN XY: 74386

Gnomad4 AFR AF: 0.0000722

Gnomad4 AMR AF: 0.000196

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.000415

Gnomad4 FIN AF: 0.0000942

Gnomad4 NFE AF: 0.000221

Gnomad4 OTH AF: 0.00

Alfa AF: 0.000241 Hom.: 0

Bravo AF: 0.000193

ESP6500AA AF: 0.00 AC: 0

ESP6500EA AF: 0.000244 AC: 2

ExAC AF: 0.000149 AC: 18

EpiCase AF: 0.000328

EpiControl AF: 0.000178

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:8 Benign:4

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not specified Uncertain:1 Benign:1

Likely benign, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Jul 30, 2024	Variant summary: TTN c.33269A>G (p.Lys11090Arg) results in a conservative amino acid change located in the I-band region of the encoded protein sequence. Five of five in-silico tools predict a benign effect of the variant on protein function. The variant allele was found at a frequency of 0.00014 in 1602136 control chromosomes in the gnomAD database (v4.1 dataset). In addition, within the South Asian subpopulation (allele frequency: 0.00037) the variant was fond in 1 homozygote. Furthermore, in certain ethnicities, e.g. in the Middle Eastern, the variant was reported with an even higher frequency (i.e. 0.0025), and which is about 6-times higher than the estimated maximum expected for a pathogenic variant in TTN causing Dilated Cardiomyopathy (0.00039), suggesting that the variant might be benign. The variant, c.33269A>G, has been reported in the literature in one individual affected with hypertrophic cardiomyopathy (Lopes_2013). These report(s) do not provide unequivocal conclusions about association of the variant with Dilated Cardiomyopathy. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. The following publication have been ascertained in the context of this evaluation (PMID: 23396983). ClinVar contains an entry for this variant (Variation ID: 178220). Based on the evidence outlined above, the variant was classified as likely benign. -
Uncertain significance, criteria provided, single submitter	clinical testing	Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine	Jul 17, 2013	The Lys11090Arg variant in TTN has not been reported in individuals with cardiom yopathy, but has been identified in 2/8212 European American chromosomes by the NHLBI Exome Sequencing Project (http://evs.gs.washington.edu/EVS/; dbSNP rs18471 321). Computational analyses (biochemical amino acid properties, conservation, A lignGVGD, PolyPhen2, and SIFT) do not provide strong support for or against an i mpact to the protein. Additional information is needed to fully assess the clini cal significance of this variant. -

not provided Uncertain:1 Benign:1

Likely benign, criteria provided, single submitter	clinical testing	GeneDx	Feb 06, 2020	This variant is associated with the following publications: (PMID: 23396983) -
Uncertain significance, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Dec 16, 2023	- -

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

Labcorp Genetics (formerly Invitae), Labcorp

Dec 21, 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. -

Cardiomyopathy Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

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

Jul 08, 2019

- -

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. -

Cardiovascular phenotype Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Mar 18, 2013

There is insufficient or conflicting evidence for classification of this alteration. -

Myopathy, myofibrillar, 9, with early respiratory failure Benign:1

Benign, 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 was too high to be consistent with this variant causing disease. Therefore, this variant is classified as benign. -

Tibial muscular dystrophy Benign:1

Benign, 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 was too high to be consistent with this variant causing disease. Therefore, this variant is classified as benign. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.10
BayesDel_addAF	Benign	-0.27	T
BayesDel_noAF	Benign	-0.31
CADD	Benign	18
DANN	Uncertain	0.98
DEOGEN2	Benign	0.027	.;.;.;.;.;.;.;T
Eigen	Benign	-0.19
Eigen_PC	Benign	-0.011
FATHMM_MKL	Uncertain	0.82	D
LIST_S2	Benign	0.85	D;D;D;.;D;D;T;T
M_CAP	Benign	0.025	T
MetaRNN	Benign	0.053	T;T;T;T;T;T;T;T
MetaSVM	Benign	-0.95	T
MutationAssessor	Benign	0.76	.;.;.;N;.;.;N;.
MutationTaster	Benign	0.98	N;N;N;N;N;N
PrimateAI	Uncertain	0.63	T
PROVEAN	Benign	-1.6	N;N;.;.;N;N;.;N
REVEL	Benign	0.073
Sift	Benign	0.35	T;T;.;.;T;T;.;D
Polyphen		0.0020	.;.;.;B;.;.;B;.
Vest4		0.29
MVP		0.37
MPC		0.069
ClinPred		0.018	T
GERP RS		4.3

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: rs184713215; hg19: chr2-179501481;