NM_001267550.2:c.83315A>T

Variant names:

• chr2-178562817-T-A
• rs578191491
• NM_001267550.2:c.83315A>T

Variant summary

Our verdict is Benign. The variant received -13 ACMG points: 0P and 13B. BP4_Strong BP6 BS1 BS2

The NM_001267550.2(TTN):​c.83315A>T​(p.Asn27772Ile) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000348 in 1,613,114 control chromosomes in the GnomAD database, including 6 homozygotes. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: 𝑓 0.0013 (5 hom., cov: 33)
  • Exomes 𝑓: 0.00025 (1 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:5 B:12
• Conservation: PhyloP100: 7.97
• Publications: 8 publications found

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

Our verdict: Benign. The variant received -13 ACMG points.

• BP4: Computational evidence support a benign effect (MetaRNN=0.024142504).
• BP6: Variant 2-178562817-T-A is Benign according to our data. Variant chr2-178562817-T-A is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 196068.
• BS1: Variant frequency is greater than expected in population amr. GnomAd4 allele frequency = 0.00127 (194/152240) while in subpopulation AMR AF = 0.0108 (165/15272). AF 95% confidence interval is 0.00946. There are 5 homozygotes in GnomAd4. There are 127 alleles in the male GnomAd4 subpopulation. Median coverage is 33. This position passed quality control check.
• BS2: High Homozygotes in GnomAd4 at 5 AD,AR gene

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTN	NM_001267550.2	c.83315A>T	p.Asn27772Ile	missense_variant	Exon 326 of 363	ENST00000589042.5	NP_001254479.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.83315A>T	p.Asn27772Ile	missense_variant	Exon 326 of 363	5	NM_001267550.2	ENSP00000467141.1

Frequencies

GnomAD3 genomes AF: 0.00128 AC: 194 AN: 152122 Hom.: 5 Cov.: 33

Gnomad AFR AF: 0.0000965

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.0108

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.000207

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.000323

Gnomad OTH AF: 0.000955

GnomAD2 exomes AF: 0.000567 AC: 140 AN: 246942 AF XY: 0.000515

Gnomad AFR exome AF: 0.000131

Gnomad AMR exome AF: 0.00294

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.000260

Gnomad OTH exome AF: 0.00134

GnomAD4 exome AF: 0.000252 AC: 368 AN: 1460874 Hom.: 1 Cov.: 37 AF XY: 0.000233 AC XY: 169 AN XY: 726704

African (AFR) AF: 0.0000598 AC: 2 AN: 33458

American (AMR) AF: 0.00287 AC: 128 AN: 44638

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26112

East Asian (EAS) AF: 0.00 AC: 0 AN: 39530

South Asian (SAS) AF: 0.00 AC: 0 AN: 86226

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53314

Middle Eastern (MID) AF: 0.000173 AC: 1 AN: 5766

European-Non Finnish (NFE) AF: 0.000193 AC: 214 AN: 1111532

Other (OTH) AF: 0.000381 AC: 23 AN: 60298

GnomAD4 genome AF: 0.00127 AC: 194 AN: 152240 Hom.: 5 Cov.: 33 AF XY: 0.00171 AC XY: 127 AN XY: 74430

African (AFR) AF: 0.0000963 AC: 4 AN: 41556

American (AMR) AF: 0.0108 AC: 165 AN: 15272

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3472

East Asian (EAS) AF: 0.00 AC: 0 AN: 5162

South Asian (SAS) AF: 0.000207 AC: 1 AN: 4824

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10614

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 294

European-Non Finnish (NFE) AF: 0.000323 AC: 22 AN: 68018

Other (OTH) AF: 0.000945 AC: 2 AN: 2116

Alfa AF: 0.000225 Hom.: 0

Bravo AF: 0.00116

ExAC AF: 0.000257 AC: 31

EpiCase AF: 0.000109

EpiControl AF: 0.000119

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:5 Benign:12

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not specified Uncertain:1 Benign:5

-

Clinical Genetics, Academic Medical Center

Significance: Benign

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Jun 11, 2015

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.Asn25204Ile variant in TTN has not been previously reported in individuals with cardiomyopathy, but has been identified in 0.1% (14/11202) of Latino chrom osomes by the Exome Aggregation Consortium (ExAC, http://exac.broadinstitute.org ; dbSNP rs578191491). Computational prediction tools and conservation analysis d o not provide strong support for or against an impact to the protein. In summary , the clinical significance of the p.Asn25204Ile variant is uncertain. -

Mar 06, 2018

Eurofins Ntd Llc (ga)

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Nov 29, 2022

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: TTN c.75611A>T (p.Asn25204Ile) results in a non-conservative amino acid change located in the A-band region of the encoded protein sequence. Four of four in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 0.0013 in 150894 control chromosomes, predominantly at a frequency of 0.011 within the Latino subpopulation in the gnomAD database (v3.1, genomes dataset), including 5 homozygotes. The variant, c.75611A>T has been reported in the literature in an individual with muscle weakness (Campuzano_2015), and in several heterozygous individuals with various cardiac phenotypes (Punetha_2016), however without convincing evidence for causality. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. Six clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation, and classified the variant as VUS (n=2), likely benign (n=3) / benign (n=1). Based on the evidence outlined above, the variant was classified as benign. -

Jan 12, 2018

GeneDx

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant is considered likely benign or benign based on one or more of the following criteria: it is a conservative change, it occurs at a poorly conserved position in the protein, it is predicted to be benign by multiple in silico algorithms, and/or has population frequency not consistent with disease. -

Apr 09, 2025

Molecular Diagnostic Laboratory for Inherited Cardiovascular Disease, Montreal Heart Institute

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

BS1;BP1 -

not provided Benign:2

-

Joint Genome Diagnostic Labs from Nijmegen and Maastricht, Radboudumc and MUMC+

Significance: Likely benign

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

-

Clinical Genetics DNA and cytogenetics Diagnostics Lab, Erasmus MC, Erasmus Medical Center

Significance: Likely benign

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

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

Jan 13, 2018

Illumina Laboratory Services, Illumina

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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

Jan 13, 2018

Illumina Laboratory Services, Illumina

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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. -

Cardiomyopathy Uncertain:1

Feb 28, 2017

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

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Early-onset myopathy with fatal cardiomyopathy Uncertain:1

Jan 13, 2018

Illumina Laboratory Services, Illumina

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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

Aug 12, 2020

PreventionGenetics, part of Exact Sciences

Significance: Likely benign

Review Status: no assertion criteria provided

Collection Method: clinical testing

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

Jan 28, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

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

Jan 13, 2018

Illumina Laboratory Services, Illumina

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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. -

Tibial muscular dystrophy Benign:1

Jan 13, 2018

Illumina Laboratory Services, Illumina

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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

Jul 22, 2020

Ambry Genetics

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

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	0.42
BayesDel_addAF	Benign	-0.25	T
BayesDel_noAF	Benign	-0.13
CADD	Benign	21
DANN	Benign	0.90
Eigen	Pathogenic	0.97
Eigen_PC	Pathogenic	0.92
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.95	D;D;D;.;D;D;D
M_CAP	Benign	0.041	D
MetaRNN	Benign	0.024	T;T;T;T;T;T;T
MetaSVM	Uncertain	0.26	D
MutationAssessor	Pathogenic	3.0	.;.;.;M;.;.;M
PhyloP100		8.0
PrimateAI	Uncertain	0.59	T
PROVEAN	Pathogenic	-6.2	D;D;.;.;D;D;.
REVEL	Uncertain	0.55
Sift	Uncertain	0.0020	D;D;.;.;D;D;.
Polyphen		1.0	.;.;.;D;.;.;D
Vest4		0.55
MutPred		0.65		.;.;.;Loss of disorder (P = 0.0808);.;.;Loss of disorder (P = 0.0808);
MVP		0.77
MPC		0.52
ClinPred		0.11	T
GERP RS		6.0
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Mutation Taster		=39/61	disease causing

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

Other links and lift over

dbSNP: rs578191491; hg19: chr2-179427544; COSMIC: COSV59977814; COSMIC: COSV59977814;