Genetic Variant HEXA:p.Trp474Cys (chr15-72345550-C-G) – ACMG Classification: Pathogenic (17 pts)

Variant summary

Our verdict is . The variant received 17 ACMG points: 17P and 0B. PS3PM1PM2PP3PP5_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 (★★). ClinVar reports functional evidence for this variant: "SCV001417469: Experimental studies have shown that this missense change affects HEXA function (PMID:9603435)." and additional evidence is available in ClinVar. 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:5

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: G2P, Genomics England PanelApp, ClinGen, Myriad Women's Health, PanelApp Australia, Labcorp Genetics (formerly Invitae)

HEXA links:

ENSG00000260729 (HGNC:):

ENSG00000260729 links:

CELF6-AS1 (HGNC:58304):

CELF6-AS1 links:

Genome browser will be placed here

new If you want to explore the variant's impact on the transcript NM_000520.6, check out the Mutation Effect Viewer. This is especially useful for frameshift variants or if you want to visualize the effect of exon loss / intron retention.

ACMG classification

Classification was made for transcript

Our verdict: Pathogenic. The variant received 17 ACMG points.

PS3

PS3 evidence extracted from ClinVar submissions: SCV001417469: Experimental studies have shown that this missense change affects HEXA function (PMID: 9603435).; SCV002041572: "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."

PM1

In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 14 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 Pathogenic/Likely_pathogenic. ClinVar VariationId is 3941.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000520.6. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
HEXA	NM_000520.6	MANE Select	c.1422G>C	p.Trp474Cys	missense splice_region	Exon 13 of 14	NP_000511.2	P06865-1
HEXA	NM_001318825.2		c.1455G>C	p.Trp485Cys	missense splice_region	Exon 13 of 14	NP_001305754.1	H3BP20
HEXA	NR_134869.3		n.1207G>C		splice_region non_coding_transcript_exon	Exon 11 of 11

Ensembl Transcripts

Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
HEXA	ENST00000268097.10	TSL:1 MANE Select	c.1422G>C	p.Trp474Cys	missense splice_region	Exon 13 of 14	ENSP00000268097.6	P06865-1
HEXA	ENST00000567159.5	TSL:1	c.1422G>C	p.Trp474Cys	missense splice_region	Exon 13 of 13	ENSP00000456489.1	H3BS10
ENSG00000260729	ENST00000379915.4	TSL:2	n.504G>C		splice_region non_coding_transcript_exon	Exon 5 of 16	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

Age Distribution

Exome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

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), 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

Age Distribution

Genome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

Alfa

AF:

0.00

Hom.:

Bravo

AF:

0.00000756

EpiCase

AF:

0.0000545

EpiControl

AF:

0.0000593

ClinVar

ClinVar submissions

Significance:Pathogenic/Likely pathogenic

Revision:criteria provided, multiple submitters, no conflicts

View on ClinVar

Pathogenic

VUS

Benign

Condition

Tay-Sachs disease (4)

GM2-GANGLIOSIDOSIS, SUBACUTE (1)

Computational scores

Source: dbNSFP v4.9

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

Eigen

Pathogenic

1.0

Eigen_PC

Pathogenic

0.94

FATHMM_MKL

Pathogenic

1.0

LIST_S2

Pathogenic

0.99

MetaRNN

Pathogenic

0.99

MetaSVM

Pathogenic

1.1

MutationAssessor

Pathogenic

3.5

PhyloP100

7.6

PrimateAI

Uncertain

0.70

PROVEAN

Pathogenic

-12

REVEL

Pathogenic

0.96

Sift

Pathogenic

0.0

Sift4G

Uncertain

0.012

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

MaxEntScan Visualizer can be used to analyze the impact of this mutation on the neighboring sequence.

Publications

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Variant Effect in Transcripts

RefSeq Transcripts

Ensembl Transcripts

Frequencies

Age Distribution

Age Distribution

ClinVar

Computational scores

Splicing

Publications

Other links and lift over