rs201057307

chr2-178621119-G-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.45599C>G(p.Ala15200Gly) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000342 in 1,612,210 control chromosomes in the GnomAD database, including 1 homozygotes. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A15200T) has been classified as Likely benign.

• Frequency:
  • Genomes: 𝑓 0.00030 (0 hom., cov: 32)
  • Exomes 𝑓: 0.00035 (1 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:6 B:12
• Conservation: PhyloP100: 9.94

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 where missense usually causes diseases, TTN
• BP4: Computational evidence support a benign effect (MetaRNN=0.009018153).
• BP6: Variant 2-178621119-G-C is Benign according to our data. Variant chr2-178621119-G-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 46991.We mark this variant Likely_benign, oryginal submissions are: {Benign=9, Uncertain_significance=6, Likely_benign=3}. Variant chr2-178621119-G-C is described in Lovd as [Benign].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTN	NM_001267550.2	c.45599C>G	p.Ala15200Gly	missense_variant	246/363	ENST00000589042.5

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTN	ENST00000589042.5	c.45599C>G	p.Ala15200Gly	missense_variant	246/363	5	NM_001267550.2	P1
TTN-AS1	ENST00000659121.1	n.502+23438G>C		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes AF: 0.000303 AC: 46 AN: 151892 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.0000657

Gnomad ASJ AF: 0.00953

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.000162

Gnomad OTH AF: 0.000479

GnomAD3 exomes AF: 0.000586 AC: 145 AN: 247242 Hom.: 0 AF XY: 0.000529 AC XY: 71 AN XY: 134156

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000584

Gnomad ASJ exome AF: 0.0116

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.000197

Gnomad OTH exome AF: 0.000834

GnomAD4 exome AF: 0.000346 AC: 505 AN: 1460318 Hom.: 1 Cov.: 32 AF XY: 0.000368 AC XY: 267 AN XY: 726442

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000673

Gnomad4 ASJ exome AF: 0.0130

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000697

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000801

Gnomad4 OTH exome AF: 0.00101

GnomAD4 genome AF: 0.000303 AC: 46 AN: 151892 Hom.: 0 Cov.: 32 AF XY: 0.000283 AC XY: 21 AN XY: 74166

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.0000657

Gnomad4 ASJ AF: 0.00953

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.000162

Gnomad4 OTH AF: 0.000479

Alfa AF: 0.00170 Hom.: 0

Bravo AF: 0.000385

ESP6500AA AF: 0.00 AC: 0

ESP6500EA AF: 0.000969 AC: 8

ExAC AF: 0.000422 AC: 51

EpiCase AF: 0.000437

EpiControl AF: 0.000415

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:6 Benign:12

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Uncertain:2 Benign:3

Benign, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Jan 01, 2024	TTN: BP4, BS1, BS2 -
Likely benign, criteria provided, single submitter	research	Biesecker Lab/Clinical Genomics Section, National Institutes of Health	Jun 24, 2013	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Genetic Services Laboratory, University of Chicago	Mar 31, 2014	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine	Jul 07, 2023	The p.Ala12632Gly variant in TTN has been reported in one heterozygous individual with hypertrophic cardiomyopathy and one compound heterozygous individual with myopathy (Lopes 2013 PMID: 23396983, Dabby 2015 PMID: 25772186). It has also been identified in 0.95% (33/3464) of Ashkenazi Jewish chromosomes and 0.016% (11/67906) of European chromosomes by gnomAD (http://gnomad.broadinstitute.org). This variant has also been reported in ClinVar (Variation ID 46991). Computational prediction tools and conservation analyses suggest that this variant may impact the protein, though this information is not predictive enough to determine pathogenicity. In summary, while the clinical significance of this variant is uncertain, these data suggest that it is more likely to be benign. ACMG/AMP Criteria applied: BS2_P, PP3. -
Likely benign, criteria provided, single submitter	clinical testing	GeneDx	Oct 15, 2020	This variant is associated with the following publications: (PMID: 27854229, 27854218, 25772186, 23861362, 23396983) -

not specified Uncertain:1 Benign:2

Uncertain significance, criteria provided, single submitter	clinical testing	Genomic Diagnostic Laboratory, Division of Genomic Diagnostics, Children's Hospital of Philadelphia	Jul 10, 2015	- -
Benign, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Jul 03, 2017	- -
Benign, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	May 18, 2023	Variant summary: TTN c.37895C>G (p.Ala12632Gly) results in a non-conservative amino acid change located in the I-band region of the encoded protein sequence. Three of five in-silico tools predict a benign effect of the variant on protein function. The variant allele was found at a frequency of 0.00059 in 247242 control chromosomes (gnomAD). The observed variant frequency is approximately equal to the estimated maximal expected allele frequency for a pathogenic variant in TTN causing Dilated Cardiomyopathy phenotype (0.00039) and within the Ashkenazi Jewish subpopulation it is seen at a frequency of 0.012, strongly suggesting that the variant is benign. c.37895C>G has been reported in the literature in settings of whole exome sequencing and multigene panel testing as a VUS in the heterozygous state in an individual affected with hypertrophic cardiomyopathy, and as a compound heterozygous genotype in two individuals with a myopathy phenotype without strong evidence for causality (e.g. Lopes_2013, Dabby_2015 Punetha_2016). Therefore, these reports do not provide unequivocal conclusions about association of the variant with disease. Additionally, a co-occurrence with a pathogenic variant has been observed (TTR c.148G>A, p.Val50Met; internal data), providing supporting evidence for a benign role. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. The following publications have been ascertained in the context of this evaluation (PMID: 25772186, 23396983, 27854218). Eleven submitters have provided clinical-significance assessments for this variant to ClinVar after 2014 and classified the variant as either benign (n=7)/likely benign (1) or VUS (n=3). Based on the evidence outlined above, the variant was classified as benign. -

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

Pathogenic, no assertion criteria provided	literature only	OMIM	Apr 17, 2019	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Illumina Laboratory Services, Illumina	Jan 12, 2018	This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Dilated cardiomyopathy 1G Uncertain:1 Benign:1

Uncertain significance, criteria provided, single submitter	clinical testing	Illumina Laboratory Services, Illumina	Jan 12, 2018	This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -
Benign, criteria provided, single submitter	clinical testing	Mendelics	May 28, 2019	- -

Early-onset myopathy with fatal cardiomyopathy Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 12, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

TTN-related disorder Benign:1

Likely benign, criteria provided, single submitter

clinical testing

PreventionGenetics, part of Exact Sciences

Aug 26, 2022

This variant is classified as likely benign based on ACMG/AMP sequence variant interpretation guidelines (Richards et al. 2015 PMID: 25741868, with internal and published modifications). -

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

Benign, criteria provided, single submitter

clinical testing

Invitae

Jan 27, 2024

- -

Cardiomyopathy Benign:1

Benign, criteria provided, single submitter

clinical testing

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

Jun 10, 2021

- -

Tibial muscular dystrophy Benign:1

Benign, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 12, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score and internal cut-off values, a variant classified as benign is not then subjected to further curation. The score for this variant resulted in a classification of benign for this disease. -

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

Benign, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 12, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score and internal cut-off values, a variant classified as benign is not then subjected to further curation. The score for this variant resulted in a classification of benign for this disease. -

Cardiovascular phenotype Benign:1

Benign, criteria provided, single submitter

clinical testing

Ambry Genetics

Nov 29, 2017

This alteration is classified as benign based on a combination of the following: seen in unaffected individuals, population frequency, intact protein function, lack of segregation with disease, co-occurrence, RNA analysis, in silico models, amino acid conservation, lack of disease association in case-control studies, and/or the mechanism of disease or impacted region is inconsistent with a known cause of pathogenicity. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.35
BayesDel_addAF	Benign	-0.24	T
BayesDel_noAF	Benign	-0.30
Cadd	Uncertain	23
Dann	Benign	0.93
Eigen	Uncertain	0.50
Eigen_PC	Uncertain	0.62
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.86	D;D;D;.;T;D;D
M_CAP	Uncertain	0.27	D
MetaRNN	Benign	0.0090	T;T;T;T;T;T;T
MetaSVM	Benign	-0.72	T
MutationTaster	Benign	1.0	D;D;D;D;D;D
PrimateAI	Uncertain	0.60	T
PROVEAN	Uncertain	-2.8	D;D;.;.;D;D;.
REVEL	Pathogenic	0.72
Sift	Uncertain	0.012	D;T;.;.;T;T;.
Polyphen		0.43	.;.;.;B;.;.;B
Vest4		0.39
MVP		0.33
MPC		0.11
ClinPred		0.16	T
GERP RS		5.7

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: rs201057307; hg19: chr2-179485846;