rs876658099

chr2-178795206-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 3P and 2B. PM2 PP2 BP4_Moderate

The NM_001267550.2(TTN):c.961G>A(p.Val321Ile) variant causes a missense change. The variant allele was found at a frequency of 0.00000137 in 1,461,858 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 14/18 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 4.73

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 Uncertain_significance. Variant got 1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant where missense usually causes diseases, TTN
• BP4: Computational evidence support a benign effect (MetaRNN=0.15799826).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTN	NM_001267550.2	c.961G>A	p.Val321Ile	missense_variant	7/363	ENST00000589042.5
TTN	NM_133379.5	c.961G>A	p.Val321Ile	missense_variant	7/46	ENST00000360870.10

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTN	ENST00000589042.5	c.961G>A	p.Val321Ile	missense_variant	7/363	5	NM_001267550.2	P1
TTN	ENST00000360870.10	c.961G>A	p.Val321Ile	missense_variant	7/46	5	NM_133379.5

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461858 Hom.: 0 Cov.: 32 AF XY: 0.00000275 AC XY: 2 AN XY: 727236

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000116

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 8.99e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine

Dec 31, 2014

The p.Val321Ile variant in TTN has not been previously reported in individuals w ith cardiomyopathy or in large population studies. Valine (Val) at position 321 is not completely conserved in evolution and 2 mammals (panda, elephant) carry a n isoleucine (Ile) at this position, raising the possibility that this change ma y be tolerated. Additional computational prediction tools do not provide strong support for or against an impact to the protein. In summary, the clinical signif icance of the p.Val321Ile variant is uncertain. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.094
BayesDel_addAF	Benign	-0.12	T
BayesDel_noAF	Benign	-0.41
Cadd	Benign	13
Dann	Benign	0.91
Eigen	Benign	-0.066
Eigen_PC	Benign	0.037
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.87	D;D;D;.;T;D;D;D
M_CAP	Benign	0.034	D
MetaRNN	Benign	0.16	T;T;T;T;T;T;T;T
MetaSVM	Benign	-0.36	T
MutationTaster	Benign	0.87	D;D;N;N;N;N;N
PrimateAI	Benign	0.48	T
PROVEAN	Benign	-0.58	N;N;.;.;N;N;.;N
REVEL	Benign	0.11
Sift	Pathogenic	0.0	D;T;.;.;T;T;.;D
Polyphen		0.0020, 0.12	.;.;.;B;.;.;B;B
Vest4		0.17
MutPred		0.25		Gain of sheet (P = 0.0344);Gain of sheet (P = 0.0344);Gain of sheet (P = 0.0344);Gain of sheet (P = 0.0344);Gain of sheet (P = 0.0344);Gain of sheet (P = 0.0344);Gain of sheet (P = 0.0344);Gain of sheet (P = 0.0344);
MVP		0.48
MPC		0.069
ClinPred		0.55	D
GERP RS		5.2

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		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: rs876658099; hg19: chr2-179659933;