rs1309123671

Variant names:

• chr5-74718363-G-A
• rs1309123671
• NM_000521.4:c.1242G>A

Variant summary

Our verdict is Pathogenic. The variant received 11 ACMG points: 11P and 0B. PM2 PP3 PP5_Very_Strong

The NM_000521.4(HEXB):​c.1242G>A​(p.Lys414Lys) variant causes a splice region, synonymous change. The variant allele was found at a frequency of 0.00000187 in 1,601,510 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: HEXB NM_000521.4 splice_region, synonymous
• Scores: Splicing: ADA: 0.9988
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 5.48
• 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 11 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: Splicing predictors support a deleterious effect. Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF, max_spliceai. No scorers claiming Uncertain. No scorers claiming Benign.
• PP5: Variant 5-74718363-G-A is Pathogenic according to our data. Variant chr5-74718363-G-A is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 558077.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
HEXB	NM_000521.4	c.1242G>A	p.Lys414Lys	splice_region_variant, synonymous_variant	Exon 10 of 14	ENST00000261416.12	NP_000512.2
HEXB	NM_001292004.2	c.567G>A	p.Lys189Lys	splice_region_variant, synonymous_variant	Exon 10 of 14		NP_001278933.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
HEXB	ENST00000261416.12	c.1242G>A	p.Lys414Lys	splice_region_variant, synonymous_variant	Exon 10 of 14	1	NM_000521.4	ENSP00000261416.7

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152160 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000241

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: 0.00

Gnomad OTH AF: 0.00

GnomAD2 exomes AF: 0.00000398 AC: 1 AN: 251298 AF XY: 0.00

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: 0.00000880

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000138 AC: 2 AN: 1449350 Hom.: 0 Cov.: 27 AF XY: 0.00 AC XY: 0 AN XY: 721818

African (AFR) AF: 0.00 AC: 0 AN: 33204

American (AMR) AF: 0.00 AC: 0 AN: 44700

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26044

East Asian (EAS) AF: 0.00 AC: 0 AN: 39592

South Asian (SAS) AF: 0.00 AC: 0 AN: 86020

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53402

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5748

European-Non Finnish (NFE) AF: 0.00000182 AC: 2 AN: 1100658

Other (OTH) AF: 0.00 AC: 0 AN: 59982

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152160 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 74338

African (AFR) AF: 0.0000241 AC: 1 AN: 41434

American (AMR) AF: 0.00 AC: 0 AN: 15268

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3466

East Asian (EAS) AF: 0.00 AC: 0 AN: 5202

South Asian (SAS) AF: 0.00 AC: 0 AN: 4832

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10616

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 316

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 68026

Other (OTH) AF: 0.00 AC: 0 AN: 2090

Alfa AF: 0.0000508 Hom.: 0

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Sandhoff disease Pathogenic:4

Feb 22, 2024

3billion

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The variant is observed at an extremely low frequency in the gnomAD v2.1.1 dataset (total allele frequency: <0.001%). Predicted Consequence/Location: Synonymous variant In silico tools predict the variant to alter splicing and produce an abnormal transcript [SpliceAI: 0.60 (>=0.2, moderate evidence for spliceogenicity)]. The variant has been reported at least twice as pathogenic with clinical assertions and evidence for the classification (ClinVar ID: VCV000558077 /PMID: 9475608). Therefore, this variant is classified as Likely pathogenic according to the recommendation of ACMG/AMP guideline. -

Apr 19, 2022

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

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: HEXB c.1242G>A (p.Lys414Lys) located at the last nucleotide of the exon alters a conserved nucleotide located adjacent to a canonical splice site and therefore could affect mRNA splicing, leading to a significantly altered protein sequence. Several computational tools predict a significant impact on normal splicing: Three predict the variant weakens the canonical 5' donor site. One predict the variant abolishes the canonical 5' splicing donor site. At least one publication reports experimental evidence that this variant affects mRNA splicing resulting in exon 10 skipping (example, Gomez-Lira_1998). The variant allele was found at a frequency of 4e-06 in 251298 control chromosomes. c.1242G>A has been reported in the literature as a homozygous and compound heterozygous genotype in at-least two individuals affected with Sandhoff Disease (example, Gomez-Lira_1998, Sobek_2012). These data indicate that the variant may be associated with disease. One clinical diagnostic laboratory has submitted clinical-significance assessments for this variant to ClinVar after 2014 and classified the variant as likely pathogenic. Based on the evidence outlined above, the variant was classified as likely pathogenic. -

May 01, 2018

Counsyl

Significance: Likely pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

This submission and the accompanying classification are no longer maintained by the submitter. For more information on current observations and classification, please contact variantquestions@myriad.com. -

Mar 07, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change affects codon 414 of the HEXB mRNA. It is a 'silent' change, meaning that it does not change the encoded amino acid sequence of the HEXB protein. RNA analysis indicates that this variant induces altered splicing and may result in an absent or disrupted protein product. This variant is present in population databases (no rsID available, gnomAD 0.004%). This variant has been observed in individual(s) with Sandhoff disease (PMID: 9475608, 23010210). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. ClinVar contains an entry for this variant (Variation ID: 558077). Variants that disrupt the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Studies have shown that this variant results in skipping of exon 10 and introduces a premature termination codon (PMID: 9475608). The resulting mRNA is expected to undergo nonsense-mediated decay. For these reasons, this variant has been classified as Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.24
CADD	Benign	20
DANN	Benign	0.91
PhyloP100		5.5
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.8
Mutation Taster		=15/85	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.98
SpliceAI score (max)		0.52		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.52		Position offset: 0

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

Other links and lift over

dbSNP: rs1309123671; hg19: chr5-74014188;