2-178526348-C-A

Position:

• chr2-178526348-C-A

Variant summary

Our verdict is Benign. Variant got -18 ACMG points: 0P and 18B. BP4_Moderate BP6_Very_Strong BA1

The NM_001267550.2(TTN):​c.*664G>T variant causes a 3 prime UTR change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0216 in 152,728 control chromosomes in the GnomAD database, including 60 homozygotes. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Likely benign (★★).

• Frequency:
  • Genomes: 𝑓 0.022 (60 hom., cov: 33)
  • Exomes 𝑓: 0.031 (0 hom.)
• Consequence: TTN NM_001267550.2 3_prime_UTR
• Clinical Significance: Benign/Likely benign criteria provided, multiple submitters, no conflicts B:7
• Conservation: PhyloP100: 0.993

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 -18 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.29).
• BP6: Variant 2-178526348-C-A is Benign according to our data. Variant chr2-178526348-C-A is described in ClinVar as [Likely_benign]. Clinvar id is 332666.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• BA1: GnomAd4 highest subpopulation (EAS) allele frequency at 95% confidence interval = 0.0587 is higher than 0.05.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTN	NM_001267550.2	c.*664G>T		3_prime_UTR_variant	363/363	ENST00000589042.5	NP_001254479.2
TTN-AS1	NR_038272.1	n.219+2712C>A		intron_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.*664G>T		3_prime_UTR_variant	363/363	5	NM_001267550.2	ENSP00000467141	P1
TTN-AS1	ENST00000659121.1	n.416+2712C>A		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes AF: 0.0216 AC: 3290 AN: 152162 Hom.: 60 Cov.: 33

Gnomad AFR AF: 0.00449

Gnomad AMI AF: 0.0307

Gnomad AMR AF: 0.0217

Gnomad ASJ AF: 0.0196

Gnomad EAS AF: 0.0641

Gnomad SAS AF: 0.00912

Gnomad FIN AF: 0.0619

Gnomad MID AF: 0.00633

Gnomad NFE AF: 0.0235

Gnomad OTH AF: 0.0196

GnomAD4 exome AF: 0.0313 AC: 14 AN: 448 Hom.: 0 Cov.: 0 AF XY: 0.0185 AC XY: 5 AN XY: 270

Gnomad4 FIN exome AF: 0.0305

Gnomad4 NFE exome AF: 0.0625

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.0216 AC: 3289 AN: 152280 Hom.: 60 Cov.: 33 AF XY: 0.0230 AC XY: 1709 AN XY: 74454

Gnomad4 AFR AF: 0.00447

Gnomad4 AMR AF: 0.0217

Gnomad4 ASJ AF: 0.0196

Gnomad4 EAS AF: 0.0644

Gnomad4 SAS AF: 0.00871

Gnomad4 FIN AF: 0.0619

Gnomad4 NFE AF: 0.0235

Gnomad4 OTH AF: 0.0194

Alfa AF: 0.0220 Hom.: 5

Bravo AF: 0.0190

Asia WGS AF: 0.0300 AC: 104 AN: 3478

ClinVar

Significance: Benign/Likely benign

Submissions summary: Benign:7

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Benign:2

Benign, criteria provided, single submitter	clinical testing	GeneDx	May 23, 2021	- -
Likely benign, criteria provided, single submitter	not provided	Breakthrough Genomics, Breakthrough Genomics	-	- -

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

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. -

Early-onset myopathy with fatal cardiomyopathy 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. -

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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.29
CADD	Benign	9.0
DANN	Benign	0.86

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: rs72629796; hg19: chr2-179391075; COSMIC: COSV60438689; COSMIC: COSV60438689;