2-178748945-A-G

Position:

• chr2-178748945-A-G

Variant summary

Our verdict is Benign. Variant got -21 ACMG points: 0P and 21B. BP4_Strong BP6_Very_Strong BP7 BS1 BS2

The NM_133379.5(TTN):​c.13455T>C​(p.Pro4485=) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00111 in 1,612,446 control chromosomes in the GnomAD database, including 13 homozygotes. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Benign (★★).

• Frequency:
  • Genomes: 𝑓 0.0044 (6 hom., cov: 32)
  • Exomes 𝑓: 0.00077 (7 hom.)
• Consequence: TTN NM_133379.5 synonymous
• Clinical Significance: Benign criteria provided, multiple submitters, no conflicts B:7
• Conservation: PhyloP100: -0.388

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 -21 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.8).
• BP6: Variant 2-178748945-A-G is Benign according to our data. Variant chr2-178748945-A-G is described in ClinVar as [Benign]. Clinvar id is 47755.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr2-178748945-A-G is described in Lovd as [Benign]. Variant chr2-178748945-A-G is described in Lovd as [Likely_benign].
• BP7: Synonymous conserved (PhyloP=-0.388 with no splicing effect.
• BS1: Variant frequency is greater than expected in population afr. gnomad4 allele frequency = 0.00439 (667/152000) while in subpopulation AFR AF= 0.014 (582/41488). AF 95% confidence interval is 0.0131. There are 6 homozygotes in gnomad4. There are 327 alleles in male gnomad4 subpopulation. Median coverage is 32. This position pass quality control queck.
• BS2: High Homozygotes in GnomAd4 at 6 AD,AR gene

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTN	NM_133379.5	c.13455T>C	p.Pro4485=	synonymous_variant	46/46	ENST00000360870.10
TTN	NM_001267550.2	c.11311+4179T>C		intron_variant		ENST00000589042.5

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTN	ENST00000360870.10	c.13455T>C	p.Pro4485=	synonymous_variant	46/46	5	NM_133379.5
TTN	ENST00000589042.5	c.11311+4179T>C		intron_variant		5	NM_001267550.2	P1
TTN-AS1	ENST00000659121.1	n.1223+5975A>G		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes AF: 0.00438 AC: 666 AN: 151882 Hom.: 6 Cov.: 32

Gnomad AFR AF: 0.0140

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00269

Gnomad ASJ AF: 0.00634

Gnomad EAS AF: 0.000193

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00316

Gnomad NFE AF: 0.000191

Gnomad OTH AF: 0.00335

GnomAD3 exomes AF: 0.00152 AC: 380 AN: 250138 Hom.: 2 AF XY: 0.00116 AC XY: 157 AN XY: 135240

Gnomad AFR exome AF: 0.0146

Gnomad AMR exome AF: 0.00122

Gnomad ASJ exome AF: 0.00557

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.0000656

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.000327

Gnomad OTH exome AF: 0.000988

GnomAD4 exome AF: 0.000772 AC: 1127 AN: 1460446 Hom.: 7 Cov.: 35 AF XY: 0.000705 AC XY: 512 AN XY: 726544

Gnomad4 AFR exome AF: 0.0143

Gnomad4 AMR exome AF: 0.00137

Gnomad4 ASJ exome AF: 0.00683

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000580

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.000267

Gnomad4 OTH exome AF: 0.00169

GnomAD4 genome AF: 0.00439 AC: 667 AN: 152000 Hom.: 6 Cov.: 32 AF XY: 0.00440 AC XY: 327 AN XY: 74318

Gnomad4 AFR AF: 0.0140

Gnomad4 AMR AF: 0.00269

Gnomad4 ASJ AF: 0.00634

Gnomad4 EAS AF: 0.000194

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.000191

Gnomad4 OTH AF: 0.00331

Alfa AF: 0.00284 Hom.: 0

Bravo AF: 0.00509

Asia WGS AF: 0.000867 AC: 3 AN: 3476

EpiCase AF: 0.000546

EpiControl AF: 0.000415

ClinVar

Significance: Benign

Submissions summary: Benign:7

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not specified Benign:3

Benign, no assertion criteria provided	clinical testing	Clinical Genetics, Academic Medical Center	-	- -
Benign, criteria provided, single submitter	clinical testing	Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine	Dec 23, 2011	- -
Benign, criteria provided, single submitter	clinical testing	GeneDx	Apr 14, 2014	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. -

not provided Benign:3

Likely benign, no assertion criteria provided	clinical testing	Diagnostic Laboratory, Department of Genetics, University Medical Center Groningen	-	- -
Benign, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Jul 01, 2024	TTN: BP4, BP7, BS1, BS2 -
Benign, criteria provided, single submitter	clinical testing	ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories	May 07, 2021	- -

TTN-related disorder Benign:1

Benign, no assertion criteria provided

clinical testing

PreventionGenetics, part of Exact Sciences

May 29, 2019

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

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.80
CADD	Benign	3.3
DANN	Benign	0.56

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: rs146470872; hg19: chr2-179613672;