chr2-178746136-G-C

Position:

• chr2-178746136-G-C

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 2P and 0B. PM2

The NM_133379.5(TTN):​c.16264C>G​(p.Pro5422Ala) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,270 control chromosomes in the GnomAD database, with no homozygous occurrence. 10/15 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: 6.8e-7 (0 hom.)
• Consequence: TTN NM_133379.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 3.38

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 Uncertain_significance. Variant got 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TTN	NM_133379.5	c.16264C>G	p.Pro5422Ala	missense_variant	46/46	ENST00000360870.10	NP_596870.2
TTN	NM_001267550.2	c.11312-4215C>G		intron_variant		ENST00000589042.5	NP_001254479.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000360870.10	c.16264C>G	p.Pro5422Ala	missense_variant	46/46	5	NM_133379.5	ENSP00000354117
TTN	ENST00000589042.5	c.11312-4215C>G		intron_variant		5	NM_001267550.2	ENSP00000467141	P1
TTN-AS1	ENST00000659121.1	n.1223+3166G>C		intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461270 Hom.: 0 Cov.: 33 AF XY: 0.00 AC XY: 0 AN XY: 726948

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: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 9.00e-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

Nov 23, 2011

The Pro5422Ala variant (TTN) has not been previously reported but has been ident ified by our laboratory in 1 individual with DCM (this individual carried 3 addi tional variants of unknown significance). Evolutionary conservation data and com putational predictions are not available for this variant and the clinical signi ficance cannot be determined at this time. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Benign	-0.085	T
BayesDel_noAF	Benign	-0.36
CADD	Benign	20
DANN	Uncertain	0.99
Eigen	Uncertain	0.52
Eigen_PC	Uncertain	0.56
FATHMM_MKL	Uncertain	0.97	D
LIST_S2	Benign	0.54	T
M_CAP	Benign	0.023	T
MetaRNN	Uncertain	0.64	D
MetaSVM	Benign	-0.59	T
MutationTaster	Benign	1.0	D;D;D;D;D;D;N
PROVEAN	Benign	0.070	N
REVEL	Benign	0.21
Sift	Benign	0.17	T
Sift4G	Benign	0.66	T
Polyphen		0.97	D
Vest4		0.59
MutPred		0.51		Loss of catalytic residue at P5422 (P = 0.1001);
MVP		0.63
ClinPred		0.41	T
GERP RS		5.9

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: rs397517820; hg19: chr2-179610863;