chr2-178647375-G-A

Variant names:

• chr2-178647375-G-A
• rs750448649
• NM_001267550.2:c.40141+6C>T

Variant summary

Our verdict is Likely benign. The variant received -4 ACMG points: 0P and 4B. BP4_Strong

The NM_001267550.2(TTN):​c.40141+6C>T variant causes a splice region, intron change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000116 in 1,549,346 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 3/3 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: 𝑓 0.000020 (0 hom., cov: 31)
  • Exomes 𝑓: 0.00013 (0 hom.)
• Consequence: TTN NM_001267550.2 splice_region, intron
• Scores: Splicing: ADA: 0.00001241
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2 B:1
• Conservation: PhyloP100: -0.605
• Publications: 0 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]

LOC124906100 (HGNC:):

ACMG classification

Our verdict: Likely_benign. The variant received -4 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.89).

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_001267550.2. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TTN	NM_001267550.2	MANE Select	c.40141+6C>T		splice_region intron	N/A	NP_001254479.2
	TTN	NM_001256850.1		c.35375-1345C>T		intron	N/A	NP_001243779.1
	TTN	NM_133378.4		c.32594-1345C>T		intron	N/A	NP_596869.4

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TTN	ENST00000589042.5	TSL:5 MANE Select	c.40141+6C>T		splice_region intron	N/A	ENSP00000467141.1
	TTN	ENST00000446966.2	TSL:1	c.40141+6C>T		splice_region intron	N/A	ENSP00000408004.2
	TTN	ENST00000436599.2	TSL:1	c.39865+6C>T		splice_region intron	N/A	ENSP00000405517.2

Frequencies

GnomAD3 genomes AF: 0.0000197 AC: 3 AN: 152100 Hom.: 0 Cov.: 31

Gnomad AFR AF: 0.0000241

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000294

Gnomad OTH AF: 0.00

GnomAD2 exomes AF: 0.0000674 AC: 10 AN: 148382 AF XY: 0.0000876

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.000186

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.000129

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.000127 AC: 177 AN: 1397246 Hom.: 0 Cov.: 30 AF XY: 0.000119 AC XY: 82 AN XY: 689134

African (AFR) AF: 0.0000317 AC: 1 AN: 31528

American (AMR) AF: 0.00 AC: 0 AN: 35678

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 25144

East Asian (EAS) AF: 0.0000560 AC: 2 AN: 35720

South Asian (SAS) AF: 0.0000379 AC: 3 AN: 79098

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 48154

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5690

European-Non Finnish (NFE) AF: 0.000157 AC: 169 AN: 1078292

Other (OTH) AF: 0.0000345 AC: 2 AN: 57942

GnomAD4 genome AF: 0.0000197 AC: 3 AN: 152100 Hom.: 0 Cov.: 31 AF XY: 0.0000135 AC XY: 1 AN XY: 74274

African (AFR) AF: 0.0000241 AC: 1 AN: 41454

American (AMR) AF: 0.00 AC: 0 AN: 15256

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

East Asian (EAS) AF: 0.00 AC: 0 AN: 5170

South Asian (SAS) AF: 0.00 AC: 0 AN: 4818

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10612

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 316

European-Non Finnish (NFE) AF: 0.0000294 AC: 2 AN: 68004

Other (OTH) AF: 0.00 AC: 0 AN: 2086

Alfa AF: 0.0000965 Hom.: 0

Bravo AF: 0.0000340

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2 Benign:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

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

Oct 24, 2017

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Autosomal recessive limb-girdle muscular dystrophy type 2J;C1838244:Tibial muscular dystrophy;C1858763:Dilated cardiomyopathy 1G;C1861065:Hypertrophic cardiomyopathy 9;C1863599:Myopathy, myofibrillar, 9, with early respiratory failure;C2673677:Early-onset myopathy with fatal cardiomyopathy Uncertain:1

Oct 14, 2021

Fulgent Genetics, Fulgent Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

TTN-related disorder Benign:1

Apr 18, 2022

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).

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.89
CADD	Benign	0.17
DANN	Benign	0.76
PhyloP100		-0.60
Mutation Taster		=97/3	polymorphism

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Benign	0.000012
dbscSNV1_RF	Benign	0.0060
SpliceAI score (max)		0.010		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: rs750448649; hg19: chr2-179512102;