2-178559409-T-C

Position:

• chr2-178559409-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.86723A>G​(p.Asn28908Ser) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000688 in 1,613,786 control chromosomes in the GnomAD database, including 1 homozygotes. In-silico tool predicts a benign outcome for this variant. 15/19 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: 𝑓 0.00019 (0 hom., cov: 33)
  • Exomes 𝑓: 0.000056 (1 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:3 B:2
• Conservation: PhyloP100: 1.51

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=0.06278923).
• BP6: Variant 2-178559409-T-C is Benign according to our data. Variant chr2-178559409-T-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 238857.We mark this variant Likely_benign, oryginal submissions are: {Likely_benign=2, Uncertain_significance=3}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTN	NM_001267550.2	c.86723A>G	p.Asn28908Ser	missense_variant	326/363	ENST00000589042.5
TTN-AS1	NR_038272.1	n.2043+17048T>C		intron_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTN	ENST00000589042.5	c.86723A>G	p.Asn28908Ser	missense_variant	326/363	5	NM_001267550.2	P1
TTN-AS1	ENST00000659121.1	n.416+35773T>C		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes AF: 0.000191 AC: 29 AN: 152218 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.000386

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000590

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.000193

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000441

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.000112 AC: 28 AN: 248988 Hom.: 1 AF XY: 0.0000888 AC XY: 12 AN XY: 135086

Gnomad AFR exome AF: 0.000387

Gnomad AMR exome AF: 0.000492

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: 0.0000443

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000561 AC: 82 AN: 1461450 Hom.: 1 Cov.: 32 AF XY: 0.0000550 AC XY: 40 AN XY: 727012

Gnomad4 AFR exome AF: 0.000179

Gnomad4 AMR exome AF: 0.000403

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.0000504

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000486

Gnomad4 OTH exome AF: 0.0000331

GnomAD4 genome AF: 0.000190 AC: 29 AN: 152336 Hom.: 0 Cov.: 33 AF XY: 0.000175 AC XY: 13 AN XY: 74482

Gnomad4 AFR AF: 0.000385

Gnomad4 AMR AF: 0.000589

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.000193

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.0000441

Gnomad4 OTH AF: 0.00

Alfa AF: 0.000174 Hom.: 0

Bravo AF: 0.000178

ESP6500AA AF: 0.00 AC: 0

ESP6500EA AF: 0.000122 AC: 1

ExAC AF: 0.0000662 AC: 8

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:3 Benign:2

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Aug 10, 2020	- -
Uncertain significance, criteria provided, single submitter	clinical testing	ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories	Aug 16, 2023	The TTN c.86723A>G; p.Asn28908Ser variant (rs377612718; ClinVar Variation ID: 238857) is rare in the general population (<0.2% allele frequency in the Genome Aggregation Database) and has not been reported in the medical literature in association with dilated cardiomyopathy (DCM) or other TTN-related disease. The clinical relevance of rare missense variants in this gene, which are identified on average once per individual sequenced in affected populations (Herman 2012), is not well understood. Yet, evidence suggests that the vast majority of such missense variants do not contribute to the clinical outcome of DCM (Begay 2015). Thus, the clinical significance of the p.Asn28908Ser variant cannot be determined with certainty. References: Begay RL et al. Role of Titin Missense Variants in Dilated Cardiomyopathy. J Am Heart Assoc. 2015 Nov 13;4(11). PMID: 26567375. Herman DS et al. Truncations of titin causing dilated cardiomyopathy. N Engl J Med. 2012 Feb 16;366(7):619-28. PMID: 22335739. Linke WA and Hamdani N. Gigantic business: titin properties and function through thick and thin. Circ Res 2014; 114(6): 1052-1068. PMID: 24625729. -

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

Nov 06, 2017

- -

not specified Benign:1

Likely benign, criteria provided, single submitter

clinical testing

GeneDx

Mar 05, 2018

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. -

Cardiovascular phenotype Benign:1

Likely benign, criteria provided, single submitter

clinical testing

Ambry Genetics

Mar 20, 2020

This alteration is classified as likely 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	0.064
BayesDel_addAF	Benign	-0.50	T
BayesDel_noAF	Benign	-0.62
CADD	Benign	13
DANN	Benign	0.90
Eigen	Benign	-0.045
Eigen_PC	Benign	0.064
FATHMM_MKL	Uncertain	0.90	D
LIST_S2	Uncertain	0.87	D;D;D;.;D;D;D
M_CAP	Benign	0.030	D
MetaRNN	Benign	0.063	T;T;T;T;T;T;T
MetaSVM	Benign	-0.68	T
MutationAssessor	Benign	1.6	.;.;.;L;.;.;L
MutationTaster	Benign	0.66	D;D;D;D;D;D
PrimateAI	Benign	0.32	T
PROVEAN	Uncertain	-2.8	D;D;.;.;D;D;.
REVEL	Benign	0.10
Sift	Benign	0.080	T;T;.;.;T;T;.
Polyphen		0.90	.;.;.;P;.;.;P
Vest4		0.16
MVP		0.13
MPC		0.068
ClinPred		0.025	T
GERP RS		4.2

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: rs377612718; hg19: chr2-179424136;