rs749563452

Positions:

• chr6-145627681-A-C
• chr6-145627681-A-G

Variant summary

Our verdict is Uncertain significance. Variant got 5 ACMG points: 5P and 0B. PM1 PM2 PP3

The NM_005670.4(EPM2A):​c.731T>G​(p.Met244Arg) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,461,792 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: EPM2A NM_005670.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 8.95

Genes affected

EPM2A (HGNC:3413): (EPM2A glucan phosphatase, laforin) This gene encodes a dual-specificity phosphatase and may be involved in the regulation of glycogen metabolism. The protein acts on complex carbohydrates to prevent glycogen hyperphosphorylation, thus avoiding the formation of insoluble aggregates. Loss-of-function mutations in this gene have been associated with Lafora disease, a rare, adult-onset recessive neurodegenerative disease, which results in myoclonus epilepsy and usually results in death several years after the onset of symptoms. The disease is characterized by the accumulation of insoluble particles called Lafora bodies, which are derived from glycogen. [provided by RefSeq, Jan 2018]

ACMG classification

Verdict is Uncertain_significance. Variant got 5 ACMG points.

• PM1: In a domain Tyrosine-protein phosphatase (size 167) in uniprot entity EPM2A_HUMAN there are 10 pathogenic changes around while only 1 benign (91%) in NM_005670.4
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.796

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
EPM2A	NM_005670.4	c.731T>G	p.Met244Arg	missense_variant	4/4	ENST00000367519.9	NP_005661.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
EPM2A	ENST00000367519.9	c.731T>G	p.Met244Arg	missense_variant	4/4	1	NM_005670.4	ENSP00000356489	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461792 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 727204

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.0000252

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 33

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Progressive myoclonic epilepsy Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Oct 03, 2020

In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive, but these predictions have not been confirmed by published functional studies and their clinical significance is uncertain. This variant has not been reported in the literature in individuals with EPM2A-related disease. This variant is present in population databases (rs749563452, ExAC 0.01%). This sequence change replaces methionine with arginine at codon 244 of the EPM2A protein (p.Met244Arg). The methionine residue is highly conserved and there is a moderate physicochemical difference between methionine and arginine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.28	D
BayesDel_noAF	Pathogenic	0.33
CADD	Pathogenic	28
DANN	Uncertain	0.98
Eigen	Uncertain	0.54
Eigen_PC	Uncertain	0.58
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Benign	0.33	T;T
M_CAP	Uncertain	0.11	D
MetaRNN	Pathogenic	0.80	D;D
MutationTaster	Benign	1.0	D
ClinPred		0.69	D
GERP RS		5.7

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: rs749563452; hg19: chr6-145948817;