chr15-72344117-A-AG

Position:

• chr15-72344117-A-AG

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PVS1_Moderate PM2 PP5_Very_Strong

The NM_000520.6(HEXA):​c.1549_1550insC​(p.Leu517ProfsTer7) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000658 in 152,072 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency: Genomes: 𝑓 0.0000066 (0 hom., cov: 32)
• Consequence: HEXA NM_000520.6 frameshift
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 3.33

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]

(HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 12 ACMG points.

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant is located in the 3'-most exon, not predicted to undergo nonsense mediated mRNA decay. Fraction of 0.0258 CDS is truncated, and there are 2 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 15-72344117-A-AG is Pathogenic according to our data. Variant chr15-72344117-A-AG is described in ClinVar as [Likely_pathogenic]. Clinvar id is 528047.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
HEXA	NM_000520.6	c.1549_1550insC	p.Leu517ProfsTer7	frameshift_variant	14/14	ENST00000268097.10
HEXA	NM_001318825.2	c.1582_1583insC	p.Leu528ProfsTer7	frameshift_variant	14/14

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
HEXA	ENST00000268097.10	c.1549_1550insC	p.Leu517ProfsTer7	frameshift_variant	14/14	1	NM_000520.6	P1
	ENST00000570175.1	n.166-1265dup		intron_variant, non_coding_transcript_variant		1

Frequencies

GnomAD3 genomes AF: 0.00000658 AC: 1 AN: 152072 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.0000655

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

GnomAD4 exome Cov.: 30

GnomAD4 genome AF: 0.00000658 AC: 1 AN: 152072 Hom.: 0 Cov.: 32 AF XY: 0.0000135 AC XY: 1 AN XY: 74302

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.0000655

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

ClinVar

Significance: Pathogenic/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	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Feb 23, 2023	Variant summary: HEXA c.1549dupC (p.Leu517ProfsX7) results in a premature termination codon which is predicted to cause a truncation of the encoded protein. Although the variant is not predicted to cause absence of the protein through nonsense mediated decay, the variant is predicted to disrupt the last 13 amino acids in the protein sequence. The variant was absent in 251476 control chromosomes (gnomAD). c.1549dupC has been reported in the literature in first-cousin parents of an infant who died of Tay-Sachs Disease (Akerman_1997). These data indicate that the variant may be associated with disease. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. One ClinVar submitter has assessed the variant since 2014: the variant was classified as pathogenic. Based on the evidence outlined above, the variant was classified as likely pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Invitae	May 15, 2023	For these reasons, this variant has been classified as Pathogenic. This variant disrupts the p.Phe521 amino acid residue in HEXA. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 25860343). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. ClinVar contains an entry for this variant (Variation ID: 528047). This premature translational stop signal has been observed in individual(s) with Tay-Sachs disease (PMID: 9150157). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. This variant is not present in population databases (gnomAD no frequency). This sequence change creates a premature translational stop signal (p.Leu517Profs*7) in the HEXA gene. While this is not anticipated to result in nonsense mediated decay, it is expected to disrupt the last 13 amino acid(s) of the HEXA protein. -

Computational scores

Source: dbNSFP v4.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.11		Details are displayed if max score is > 0.2

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

Publications

LitVar

Other links and lift over

dbSNP: rs1555472161; hg19: chr15-72636458;