rs1555473138

Positions:

• chr15-72353688-T-TA

Variant summary

Our verdict is Pathogenic. Variant got 11 ACMG points: 11P and 0B. PM2 PP3 PP5_Very_Strong

The NM_000520.6(HEXA):​c.459+2_459+3insT variant causes a splice region, intron change. The variant was absent in control chromosomes in GnomAD project. 1/1 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: HEXA NM_000520.6 splice_region, intron
• Clinical Significance: Likely pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 6.33

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]

ACMG classification

Verdict is Pathogenic. Variant got 11 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: max_spliceai. No scorers claiming Uncertain. No scorers claiming Benign.
• PP5: Variant 15-72353688-T-TA is Pathogenic according to our data. Variant chr15-72353688-T-TA is described in ClinVar as [Likely_pathogenic]. Clinvar id is 558071.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
HEXA	NM_000520.6	c.459+2_459+3insT		splice_region_variant, intron_variant		ENST00000268097.10	NP_000511.2
HEXA	NM_001318825.2	c.492+2_492+3insT		splice_region_variant, intron_variant			NP_001305754.1
HEXA	NR_134869.3	n.501+2_501+3insT		splice_region_variant, intron_variant, non_coding_transcript_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
HEXA	ENST00000268097.10	c.459+2_459+3insT		splice_region_variant, intron_variant		1	NM_000520.6	ENSP00000268097	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 29

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Tay-Sachs disease Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Jan 21, 2024	This sequence change falls in intron 4 of the HEXA gene. It does not directly change the encoded amino acid sequence of the HEXA protein. RNA analysis indicates that this variant induces altered splicing and may result in an absent or disrupted protein product. This variant is not present in population databases (gnomAD no frequency). This variant has been observed in individual(s) with Tay-Sachs disease (PMID: 9090529). It has also been observed to segregate with disease in related individuals. This variant is also known as +3tIVS4. ClinVar contains an entry for this variant (Variation ID: 558071). 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 4 and introduces a premature termination codon (PMID: 9090529). The resulting mRNA is expected to undergo nonsense-mediated decay. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -
Likely pathogenic, criteria provided, single submitter	clinical testing	Counsyl	Apr 30, 2018	- -

Computational scores

Source: dbNSFP v4.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.62		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.62		Position offset: 3

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

Publications

LitVar

Other links and lift over

dbSNP: rs1555473138; hg19: chr15-72646029;