rs55892860

Positions:

• chr2-178783780-T-A
• chr2-178783780-T-G

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 2P and 4B. PM2 BP4_Moderate BP6 BP7

The NM_001267550.2(TTN):​c.2781A>T​(p.Thr927Thr) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000658 in 151,996 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in Lovd as Likely benign (no stars). Synonymous variant affecting the same amino acid position (i.e. T927T) has been classified as Benign.

• Frequency: Genomes: 𝑓 0.0000066 (0 hom., cov: 32)
• Consequence: TTN NM_001267550.2 synonymous
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 0.300

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]

ACMG classification

Verdict is Likely_benign. Variant got -2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.41).
• BP6: Variant 2-178783780-T-A is Benign according to our data. Variant chr2-178783780-T-A is described in Lovd as [Likely_benign].
• BP7: Synonymous conserved (PhyloP=0.3 with no splicing effect.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTN	NM_001267550.2	c.2781A>T	p.Thr927Thr	synonymous_variant	17/363	ENST00000589042.5	NP_001254479.2
TTN	NM_133379.5	c.2781A>T	p.Thr927Thr	synonymous_variant	17/46	ENST00000360870.10	NP_596870.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.2781A>T	p.Thr927Thr	synonymous_variant	17/363	5	NM_001267550.2	ENSP00000467141.1
TTN	ENST00000360870.10	c.2781A>T	p.Thr927Thr	synonymous_variant	17/46	5	NM_133379.5	ENSP00000354117.4

Frequencies

GnomAD3 genomes AF: 0.00000658 AC: 1 AN: 151996 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000242

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: 0.00

Gnomad OTH AF: 0.00

GnomAD4 exome Cov.: 30

GnomAD4 genome AF: 0.00000658 AC: 1 AN: 151996 Hom.: 0 Cov.: 32 AF XY: 0.0000135 AC XY: 1 AN XY: 74234

Gnomad4 AFR AF: 0.0000242

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.41
CADD	Benign	8.0
DANN	Benign	0.84

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: rs55892860; hg19: chr2-179648507;