rs55660660

Positions:

• chr2-178542266-A-G
• chr2-178542266-A-T

Variant summary

Our verdict is Benign. Variant got -12 ACMG points: 1P and 13B. PP2 BP4_Strong BP6 BS1 BS2

The NM_001267550.2(TTN):​c.97490T>C​(p.Ile32497Thr) variant causes a missense, splice region change. The variant allele was found at a frequency of 0.000496 in 1,604,922 control chromosomes in the GnomAD database, including 9 homozygotes. In-silico tool predicts a benign outcome for this variant. 11/18 in silico tools predict a benign outcome for this variant. 1/1 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: 𝑓 0.0024 (3 hom., cov: 32)
  • Exomes 𝑓: 0.00029 (6 hom.)
• Consequence: TTN NM_001267550.2 missense, splice_region
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:1 B:15
• Conservation: PhyloP100: 5.45

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 Benign. Variant got -12 ACMG points.

• PP2: Missense variant where missense usually causes diseases, TTN
• BP4: Computational evidence support a benign effect (MetaRNN=0.0065636635).
• BP6: Variant 2-178542266-A-G is Benign according to our data. Variant chr2-178542266-A-G is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 96321.We mark this variant Likely_benign, oryginal submissions are: {Benign=11, Likely_benign=4, Uncertain_significance=1}. Variant chr2-178542266-A-G is described in Lovd as [Likely_benign]. Variant chr2-178542266-A-G is described in Lovd as [Benign].
• BS1: Variant frequency is greater than expected in population afr. gnomad4 allele frequency = 0.00242 (369/152224) while in subpopulation AFR AF= 0.00823 (342/41556). AF 95% confidence interval is 0.00751. There are 3 homozygotes in gnomad4. There are 188 alleles in male gnomad4 subpopulation. Median coverage is 32. This position pass quality control queck.
• BS2: High Homozygotes in GnomAd4 at 3 AD,AR gene

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTN	NM_001267550.2	c.97490T>C	p.Ile32497Thr	missense_variant, splice_region_variant	349/363	ENST00000589042.5
TTN-AS1	NR_038272.1	n.1948A>G		non_coding_transcript_exon_variant	7/17

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTN	ENST00000589042.5	c.97490T>C	p.Ile32497Thr	missense_variant, splice_region_variant	349/363	5	NM_001267550.2	P1
TTN-AS1	ENST00000659121.1	n.416+18630A>G		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes AF: 0.00243 AC: 369 AN: 152106 Hom.: 3 Cov.: 32

Gnomad AFR AF: 0.00825

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000852

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: 0.000132

Gnomad OTH AF: 0.00191

GnomAD3 exomes AF: 0.000587 AC: 141 AN: 240098 Hom.: 0 AF XY: 0.000507 AC XY: 66 AN XY: 130216

Gnomad AFR exome AF: 0.00838

Gnomad AMR exome AF: 0.000119

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.0000339

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.000102

Gnomad OTH exome AF: 0.000512

GnomAD4 exome AF: 0.000294 AC: 427 AN: 1452698 Hom.: 6 Cov.: 32 AF XY: 0.000305 AC XY: 220 AN XY: 721240

Gnomad4 AFR exome AF: 0.00859

Gnomad4 AMR exome AF: 0.000227

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000235

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000606

Gnomad4 OTH exome AF: 0.000816

GnomAD4 genome AF: 0.00242 AC: 369 AN: 152224 Hom.: 3 Cov.: 32 AF XY: 0.00253 AC XY: 188 AN XY: 74436

Gnomad4 AFR AF: 0.00823

Gnomad4 AMR AF: 0.000851

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.000208

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.000132

Gnomad4 OTH AF: 0.00189

Alfa AF: 0.000552 Hom.: 1

Bravo AF: 0.00269

ESP6500AA AF: 0.00568 AC: 23

ESP6500EA AF: 0.000119 AC: 1

ExAC AF: 0.000711 AC: 86

Asia WGS AF: 0.000289 AC: 1 AN: 3478

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:1 Benign:15

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not specified Benign:5

Benign, criteria provided, single submitter	clinical testing	Athena Diagnostics	Feb 13, 2017	- -
Benign, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	May 03, 2021	Variant summary: TTN c.89786T>C (p.Ile29929Thr) results in a non-conservative amino acid change located in the A-band region (cardiodb.org) of the encoded protein sequence. Three of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 0.00059 in 240098 control chromosomes, predominantly at a frequency of 0.0084 within the African or African-American subpopulation in the gnomAD database. The observed variant frequency within African or African-American control individuals in the gnomAD database is approximately 21.5 -fold the estimated maximal expected allele frequency for a pathogenic variant in TTN causing Dilated Cardiomyopathy phenotype (0.00039), strongly suggesting that the variant is a benign polymorphism found primarily in populations of African or African-American origin. Ten clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation, citing the variant as benign/likely benign (n=9) and uncertain significance (n=1). Based on the evidence outlined above, the variant was classified as benign. -
Benign, criteria provided, single submitter	clinical testing	GeneDx	Apr 08, 2015	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. -
Benign, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Jun 09, 2015	- -
Benign, criteria provided, single submitter	clinical testing	Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine	Apr 01, 2015	p.Ile29929Thr in exon 298 of TTN: This variant is not expected to have clinical significance because it has been identified in 1.0% (69/6716) of African chromos omes by the Exome Aggregation Consortium (ExAC, http://exac.broadinstitute.org; dbSNP rs55660660). -

not provided Benign:2

Likely benign, criteria provided, single submitter	clinical testing	ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories	Nov 29, 2023	- -
Likely benign, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Jan 01, 2023	TTN: BS2 -

Autosomal recessive limb-girdle muscular dystrophy type 2J 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. -

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

Benign, criteria provided, single submitter

clinical testing

Invitae

Feb 01, 2024

- -

Dilated cardiomyopathy 1G Benign:1

Likely 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 likely benign is not then subjected to further curation. The score for this variant resulted in a classification of likely benign for this disease. -

Cardiomyopathy Benign:1

Benign, criteria provided, single submitter

clinical testing

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

Jun 06, 2023

- -

Early-onset myopathy with fatal cardiomyopathy Benign:1

Likely 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 likely benign is not then subjected to further curation. The score for this variant resulted in a classification of likely 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. -

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. -

Primary dilated cardiomyopathy Benign:1

Benign, criteria provided, single submitter

clinical testing

Center for Advanced Laboratory Medicine, UC San Diego Health, University of California San Diego

May 08, 2019

- -

Cardiovascular phenotype Benign:1

Benign, criteria provided, single submitter

clinical testing

Ambry Genetics

Oct 23, 2015

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	Benign	0.16
BayesDel_addAF	Benign	-0.34	T
BayesDel_noAF	Benign	-0.26
CADD	Benign	19
DANN	Benign	0.72
Eigen	Uncertain	0.36
Eigen_PC	Uncertain	0.48
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Benign	0.85	T;T;T;.;T;T;T
MetaRNN	Benign	0.0066	T;T;T;T;T;T;T
MetaSVM	Benign	-0.88	T
MutationTaster	Benign	1.0	D;D;D;D;D;D
PrimateAI	Uncertain	0.75	T
PROVEAN	Uncertain	-2.5	D;D;.;.;D;D;.
REVEL	Benign	0.18
Sift	Uncertain	0.015	D;D;.;.;D;D;.
Polyphen		0.92	.;.;.;P;.;.;P
Vest4		0.53
MVP		0.57
MPC		0.18
ClinPred		0.036	T
GERP RS		6.2
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7

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: rs55660660; hg19: chr2-179406993;