5-74689474-G-C

Variant names:

• chr5-74689474-G-C
• rs761197472
• NM_000521.4:c.445+1G>C

Variant summary

Our verdict is Pathogenic. The variant received 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000521.4(HEXB):​c.445+1G>C variant causes a splice donor, intron change. The variant allele was found at a frequency of 0.00000137 in 1,460,508 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: HEXB NM_000521.4 splice_donor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 5.71
• Publications: 1 publications found

Genes affected

HEXB (HGNC:4879): (hexosaminidase subunit beta) Hexosaminidase B is the beta subunit of the lysosomal enzyme beta-hexosaminidase that, together with the cofactor GM2 activator protein, catalyzes the degradation of the ganglioside GM2, and other molecules containing terminal N-acetyl hexosamines. Beta-hexosaminidase is composed of two subunits, alpha and beta, which are encoded by separate genes. Both beta-hexosaminidase alpha and beta subunits are members of family 20 of glycosyl hydrolases. Mutations in the alpha or beta subunit genes lead to an accumulation of GM2 ganglioside in neurons and neurodegenerative disorders termed the GM2 gangliosidoses. Beta subunit gene mutations lead to Sandhoff disease (GM2-gangliosidosis type II). Alternatively spliced transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, May 2014]

HEXB Gene-Disease associations (from GenCC):

• Sandhoff disease

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

ACMG classification

Our verdict: Pathogenic. The variant received 18 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, Cryptic splice site detected, with MaxEntScore 7.8, offset of 17, new splice context is: aatGTgagt. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 5-74689474-G-C is Pathogenic according to our data. Variant chr5-74689474-G-C is described in ClinVar as Pathogenic. ClinVar VariationId is 256358.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000521.4. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	HEXB	NM_000521.4	MANE Select	c.445+1G>C		splice_donor intron	N/A	NP_000512.2
	HEXB	NM_001292004.2		c.-231+1G>C		splice_donor intron	N/A	NP_001278933.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	HEXB	ENST00000261416.12	TSL:1 MANE Select	c.445+1G>C		splice_donor intron	N/A	ENSP00000261416.7
	HEXB	ENST00000511181.5	TSL:1	c.-231+1G>C		splice_donor intron	N/A	ENSP00000426285.1
	HEXB	ENST00000515528.1	TSL:2	n.501G>C		non_coding_transcript_exon	Exon 2 of 2

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1460508 Hom.: 0 Cov.: 30 AF XY: 0.00000138 AC XY: 1 AN XY: 726708

African (AFR) AF: 0.00 AC: 0 AN: 33444

American (AMR) AF: 0.00 AC: 0 AN: 44720

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26124

East Asian (EAS) AF: 0.00 AC: 0 AN: 39684

South Asian (SAS) AF: 0.00 AC: 0 AN: 86234

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53408

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 0.00000180 AC: 2 AN: 1110780

Other (OTH) AF: 0.00 AC: 0 AN: 60346

GnomAD4 genome Cov.: 33

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.00000378

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Sandhoff disease Pathogenic:4

May 01, 2025

Natera, Inc.

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

Mar 15, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

For these reasons, this variant has been classified as Pathogenic. Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. ClinVar contains an entry for this variant (Variation ID: 256358). Disruption of this splice site has been observed in individual(s) with Sandhoff disease (PMID: 22848519, 31852446). This variant is not present in population databases (gnomAD no frequency). This sequence change affects a donor splice site in intron 2 of the HEXB gene. It is expected to disrupt RNA splicing. Variants that disrupt the donor or acceptor splice site typically lead to a loss of protein function (PMID: 16199547), and loss-of-function variants in HEXB are known to be pathogenic (PMID: 7550345, 18758829).

Feb 12, 2021

Foundation for Research in Genetics and Endocrinology, FRIGE's Institute of Human Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

A homozygous 3’ splice site variation in intron 2 of the HEXB gene was detected. The observed variant c.445+1G>C has not been reported in the 1000 genomes and ExAC databases. The in silico prediction of the variant is damaging by MutationTaster2. In summary, the variant meets our criteria to be classified as pathogenic.

Sep 11, 2018

PreventionGenetics, part of Exact Sciences

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.40	D
BayesDel_noAF	Pathogenic	0.33
CADD	Pathogenic	34
DANN	Uncertain	1.0
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.98
FATHMM_MKL	Pathogenic	0.99	D
PhyloP100		5.7
GERP RS		6.0
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Mutation Taster		=1/99	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.93
SpliceAI score (max)		0.95		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.20		Position offset: 16
DS_DL_spliceai		0.95		Position offset: -1

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

Other links and lift over

dbSNP: rs761197472; hg19: chr5-73985299;