rs121907981

Variant names:

Variant summary

Our verdict is Pathogenic. The variant received 13 ACMG points: 13P and 0B. PM1PM2PP3PP5_Very_Strong

The NM_000520.6(HEXA):c.1422G>C(p.Trp474Cys) variant causes a missense, splice region change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000372 in 1,614,016 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 13/23 in silico tools predict a damaging outcome for this variant. 2/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. W474L) has been classified as Uncertain significance.

Frequency

Genomes: 𝑓 0.0000066 ( 0 hom., cov: 34)

Exomes 𝑓: 0.0000034 ( 0 hom. )

Consequence

HEXA
NM_000520.6 missense, splice_region

Scores

Splicing: ADA: 0.9997

Clinical Significance

Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:4

Conservation

PhyloP100: 7.56

Publications

8 publications found

Variant links:

Genes affected

HEXA (HGNC:4878): (hexosaminidase subunit alpha) This gene encodes a member of the glycosyl hydrolase 20 family of proteins. The encoded preproprotein is proteolytically processed to generate the alpha subunit of the lysosomal enzyme beta-hexosaminidase. This enzyme, together with the cofactor GM2 activator protein, catalyzes the degradation of the ganglioside GM2, and other molecules containing terminal N-acetyl hexosamines. Mutations in this gene lead to an accumulation of GM2 ganglioside in neurons, the underlying cause of neurodegenerative disorders termed the GM2 gangliosidoses, including Tay-Sachs disease (GM2-gangliosidosis type I). Alternative splicing results in multiple transcript variants, at least one of which encodes a preproprotein that is proteolytically processed. [provided by RefSeq, Jan 2016]

HEXA Gene-Disease associations (from GenCC):

Tay-Sachs disease
Inheritance: AR Classification: DEFINITIVE, STRONG Submitted by: Myriad Women’s Health, Genomics England PanelApp, G2P, Labcorp Genetics (formerly Invitae), ClinGen

HEXA links:

ENSG00000260729 (HGNC:):

ENSG00000260729 links:

ENSG00000261460 (HGNC:58304):

ENSG00000261460 links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Pathogenic. The variant received 13 ACMG points.

PM1

In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 9 uncertain in NM_000520.6

PM2

Very rare variant in population databases, with high coverage;

PP3

Splicing predictors support a deleterious effect. Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF. No scorers claiming Uncertain. Scorers claiming Benign: max_spliceai.

PP5

Variant 15-72345550-C-G is Pathogenic according to our data. Variant chr15-72345550-C-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 3941.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
HEXA	NM_000520.6 link	c.1422G>C	p.Trp474Cys	missense_variant, splice_region_variant	Exon 13 of 14	ENST00000268097.10	NP_000511.2	P06865-1A0A0S2Z3W3
HEXA	NM_001318825.2 link	c.1455G>C	p.Trp485Cys	missense_variant, splice_region_variant	Exon 13 of 14		NP_001305754.1	P06865H3BP20B4DVA7
HEXA	NR_134869.3 link	n.1207G>C		splice_region_variant, non_coding_transcript_exon_variant	Exon 11 of 11

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
HEXA	ENST00000268097.10 link	c.1422G>C	p.Trp474Cys	missense_variant, splice_region_variant	Exon 13 of 14	1	NM_000520.6	ENSP00000268097.6		P06865-1
ENSG00000260729	ENST00000379915.4 link	n.504G>C		splice_region_variant, non_coding_transcript_exon_variant	Exon 5 of 16	2		ENSP00000478716.1		A0A087WUJ7

Frequencies

GnomAD3 genomes

AF:

0.00000657

AC:

AN:

152252

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

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:

0.0000147

Gnomad OTH

AF:

0.00

GnomAD2 exomes

AF:

0.0000119

AC:

AN:

251254

AF XY:

0.00

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.0000264

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000342

AC:

AN:

1461764

Hom.:

Cov.:

AF XY:

0.00000275

AC XY:

AN XY:

727172

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

33478

American (AMR)

AF:

0.00

AC:

AN:

44720

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26132

East Asian (EAS)

AF:

0.00

AC:

AN:

39698

South Asian (SAS)

AF:

0.00

AC:

AN:

86244

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53370

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5760

European-Non Finnish (NFE)

AF:

0.00000450

AC:

AN:

1111974

Other (OTH)

AF:

0.00

AC:

AN:

60388

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.465

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

GnomAD4 genome

AF:

0.00000657

AC:

AN:

152252

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

74386

show subpopulations

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5.

African (AFR)

AF:

0.00

AC:

AN:

41460

American (AMR)

AF:

0.00

AC:

AN:

15290

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3472

East Asian (EAS)

AF:

0.00

AC:

AN:

5196

South Asian (SAS)

AF:

0.00

AC:

AN:

4834

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10626

Middle Eastern (MID)

AF:

0.00

AC:

AN:

316

European-Non Finnish (NFE)

AF:

0.0000147

AC:

AN:

68052

Other (OTH)

AF:

0.00

AC:

AN:

2094

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5. (p-value = 0.000000), which strongly suggests a high chance of mosaicism in these individuals.

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.375

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Alfa

AF:

0.00

Hom.:

Bravo

AF:

0.00000756

ExAC

AF:

0.0000165

AC:

EpiCase

AF:

0.0000545

EpiControl

AF:

0.0000593

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

Tay-Sachs disease

Pathogenic:3

Nov 28, 2021

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance:Pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Variant summary: HEXA c.1422G>C (p.Trp474Cys) results in a non-conservative amino acid change located in the Glycoside hydrolase family 20, catalytic domain (IPR015883) of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 1.2e-05 in 251254 control chromosomes. c.1422G>C has been reported in the literature as a compound heterozygous genotype in at-least two affected sibling individuals with Tay-Sachs Disease who have been subsequently cited by others and included in clinical trials (example, Petroulakis_1998, Neudorfer_2005, Clarke_2011). These data indicate that the variant is likely to be associated with disease. At least one publication reports variant specific experimental evidence evaluating an impact on protein function (Petroulakis_1998). The most pronounced variant effect results in <10% of normal enzyme activity measured as expressed levels of alpha-subunit activity in COS-7 cells. One clinical diagnostic laboratory has submitted clinical-significance assessments for this variant to ClinVar after 2014 and classified the variant as pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -

Dec 11, 2019

Revvity Omics, Revvity

Significance:Likely pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

- -

Jan 14, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

This sequence change replaces tryptophan, which is neutral and slightly polar, with cysteine, which is neutral and slightly polar, at codon 474 of the HEXA protein (p.Trp474Cys). This variant is present in population databases (rs121907981, gnomAD 0.003%). This missense change has been observed in individual(s) with Tay-Sachs disease (PMID: 9603435). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 3941). An algorithm developed to predict the effect of missense changes on protein structure and function (PolyPhen-2) suggests that this variant is likely to be disruptive. Experimental studies have shown that this missense change affects HEXA function (PMID: 9603435). For these reasons, this variant has been classified as Pathogenic. -

Gm2-gangliosidosis, subacute

Pathogenic:1

Jan 01, 1998

OMIM

Significance:Pathogenic

Review Status:no assertion criteria provided

Collection Method:literature only

- -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Pathogenic

0.99

BayesDel_addAF

Pathogenic

0.52

BayesDel_noAF

Pathogenic

0.57

CADD

Pathogenic

(source)

DANN

Uncertain

0.99

DEOGEN2

Pathogenic

0.98

D;.;D

Eigen

Pathogenic

1.0

Eigen_PC

Pathogenic

0.94

FATHMM_MKL

Pathogenic

1.0

LIST_S2

Pathogenic

0.99

D;D;D

MetaRNN

Pathogenic

0.99

D;D;D

MetaSVM

Pathogenic

1.1

MutationAssessor

Pathogenic

3.5

H;.;.

PhyloP100

7.6

PrimateAI

Uncertain

0.70

PROVEAN

Pathogenic

-12

D;D;D

REVEL

Pathogenic

0.96

Sift

Pathogenic

0.0

D;D;D

Sift4G

Uncertain

0.012

D;D;D

Polyphen

1.0

D;.;.

Vest4

0.98

MutPred

0.97

Loss of MoRF binding (P = 0.0191);.;Loss of MoRF binding (P = 0.0191);

MVP

1.0

MPC

0.95

ClinPred

1.0

GERP RS

5.7

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.7

Varity_R

0.98

gMVP

0.99

Mutation Taster

=1/99

disease causing (ClinVar)

(source)

Splicing

Name

Calibrated prediction

Score

Prediction

dbscSNV1_ADA

Pathogenic

1.0

dbscSNV1_RF

Pathogenic

0.93

SpliceAI score (max)

0.10

Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

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rs121907981

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over