15-72350574-C-T

Variant names:

• chr15-72350574-C-T
• rs121907959
• NM_000520.6:c.749G>A

Variant summary

Our verdict is Pathogenic. The variant received 18 ACMG points: 18P and 0B. PM1 PM2 PM5 PP3_Strong PP5_Very_Strong

The NM_000520.6(HEXA):​c.749G>A​(p.Gly250Asp) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. G250S) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: HEXA NM_000520.6 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 7.81
• Publications: 12 publications found

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

ENSG00000261460 (HGNC:58304):

ENSG00000260729 (HGNC:):

ACMG classification

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

• PM1: In a hotspot region, there are 4 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 2 benign, 6 uncertain in NM_000520.6
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr15-72350575-C-T is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 381668.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.99
• PP5: Variant 15-72350574-C-T is Pathogenic according to our data. Variant chr15-72350574-C-T is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 3902.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
HEXA	NM_000520.6	c.749G>A	p.Gly250Asp	missense_variant	Exon 7 of 14	ENST00000268097.10	NP_000511.2
HEXA	NM_001318825.2	c.782G>A	p.Gly261Asp	missense_variant	Exon 7 of 14		NP_001305754.1
HEXA	NR_134869.3	n.791G>A		non_coding_transcript_exon_variant	Exon 7 of 11

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
HEXA	ENST00000268097.10	c.749G>A	p.Gly250Asp	missense_variant	Exon 7 of 14	1	NM_000520.6	ENSP00000268097.6
ENSG00000260729	ENST00000379915.4	n.413-4249G>A		intron_variant	Intron 3 of 15	2		ENSP00000478716.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

Alfa AF: 0.00 Hom.: 0

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Tay-Sachs disease Pathogenic:3

Apr 18, 2024

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

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: HEXA c.749G>A (p.Gly250Asp) results in a non-conservative amino acid change located in the Glycoside hydrolase family 20, catalytic domain (IPR015883) of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 251484 control chromosomes. c.749G>A has been reported in the literature in multiple homozygous individuals affected with Tay-Sachs Disease (e.g. Trop_1992). These data indicate that the variant is likely to be associated with disease. At least one publication reports experimental evidence evaluating an impact on protein function. The most pronounced variant effect results in <10% of normal enzyme activity in vitro (e.g. Trop_1992). The following publication has been ascertained in the context of this evaluation (PMID: 1301189). ClinVar contains an entry for this variant (Variation ID: 3902). Based on the evidence outlined above, the variant was classified as pathogenic. -

Nov 17, 2022

Institute of Medical Genetics and Applied Genomics, University Hospital Tübingen

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Mar 22, 2022

Institute of Human Genetics, University of Leipzig Medical Center

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was identified as homozygous._x000D_ Criteria applied: PM3, PM5, PM2_SUP, PP3 -

Tay-sachs disease, juvenile Pathogenic:1

Jan 01, 1992

OMIM

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: literature only

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.97
BayesDel_addAF	Pathogenic	0.58	D
BayesDel_noAF	Pathogenic	0.60
CADD	Pathogenic	26
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.98	D;.;D
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	1.0
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	0.99	D;D;D
M_CAP	Uncertain	0.15	D
MetaRNN	Pathogenic	0.99	D;D;D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Pathogenic	4.3	H;.;.
PhyloP100		7.8
PrimateAI	Uncertain	0.77	T
PROVEAN	Pathogenic	-6.8	D;D;D
REVEL	Pathogenic	0.94
Sift	Uncertain	0.0010	D;D;D
Sift4G	Pathogenic	0.0010	D;D;D
Polyphen		1.0	D;.;.
Vest4		0.99
MutPred		0.96		Loss of methylation at R247 (P = 0.0554);.;Loss of methylation at R247 (P = 0.0554);
MVP		1.0
MPC		0.86
ClinPred		1.0	D
GERP RS		5.9
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.99
gMVP		0.95
Mutation Taster		=0/100	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		Details are displayed if max score is > 0.2

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

Other links and lift over

dbSNP: rs121907959; hg19: chr15-72642915;