rs121907973

Positions:

• chr15-72351215-T-G

Variant summary

Our verdict is Likely pathogenic. Variant got 9 ACMG points: 9P and 0B. PM1 PM2 PP3_Strong PP5

The ENST00000268097.10(HEXA):​c.590A>C​(p.Lys197Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000343 in 1,456,736 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000034 (0 hom.)
• Consequence: HEXA ENST00000268097.10 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:3 U:3
• Conservation: PhyloP100: 7.92

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 Likely_pathogenic. Variant got 9 ACMG points.

• PM1: In a hotspot region, there are 4 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 8 uncertain in ENST00000268097.10
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.98
• PP5: Variant 15-72351215-T-G is Pathogenic according to our data. Variant chr15-72351215-T-G is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 3927.We mark this variant Likely_pathogenic, oryginal submissions are: {Likely_pathogenic=2, Uncertain_significance=3}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
HEXA	NM_000520.6	c.590A>C	p.Lys197Thr	missense_variant	6/14	ENST00000268097.10	NP_000511.2
HEXA	NM_001318825.2	c.623A>C	p.Lys208Thr	missense_variant	6/14		NP_001305754.1
HEXA	NR_134869.3	n.632A>C		non_coding_transcript_exon_variant	6/11

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
HEXA	ENST00000268097.10	c.590A>C	p.Lys197Thr	missense_variant	6/14	1	NM_000520.6	ENSP00000268097	P1
	ENST00000570175.1	n.2569T>G		non_coding_transcript_exon_variant	3/3	1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251472 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 135906

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 SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000879

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000343 AC: 5 AN: 1456736 Hom.: 0 Cov.: 28 AF XY: 0.00000414 AC XY: 3 AN XY: 725070

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000452

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Alfa AF: 0.0000239 Hom.: 0

Bravo AF: 0.00000378

ESP6500AA AF: 0.00 AC: 0

ESP6500EA AF: 0.000116 AC: 1

ExAC AF: 0.00000824 AC: 1

EpiCase AF: 0.00

EpiControl AF: 0.0000593

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:3 Uncertain:3

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Mar 01, 2022	HEXA: PM3:Strong, PM2, PP3, PP4 -
Likely pathogenic, criteria provided, single submitter	clinical testing	Mayo Clinic Laboratories, Mayo Clinic	Apr 23, 2019	PS3, PM2, PM3, PP3 -

Tay-Sachs disease Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Counsyl	May 16, 2018	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Oct 16, 2021	This sequence change replaces lysine with threonine at codon 197 of the HEXA protein (p.Lys197Thr). The lysine residue is highly conserved and there is a moderate physicochemical difference between lysine and threonine. This variant is present in population databases (rs121907973, ExAC 0.001%). This variant has been observed in individual(s) with Tay-Sachs disease (PMID: 8490625). ClinVar contains an entry for this variant (Variation ID: 3927). Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive. Studies have shown that this variant does not significantly alter or has an unclear effect on HEXA gene expression (PMID: 8490625). In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Gm2-gangliosidosis, late onset Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

OMIM

Jan 01, 1993

- -

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

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

Nov 28, 2021

Variant summary: HEXA c.590A>C (p.Lys197Thr) 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 allele was found at a frequency of 4e-06 in 251472 control chromosomes. The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. c.590A>C has been reported in the literature as a compound heterozygous genotype in at-least one individual affected with adult onset Tay-Sachs Disease who has been subsequently cited by others (example, Akli_1993). To our knowledge, no variant specific experimental evidence demonstrating an impact on protein function has been reported. Two clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation. One laboratory classified the variant as likely pathogenic, and one laboratory classified the variant as uncertain significance. Based on the evidence outlined above, the variant was classified as VUS-possibly pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.98
BayesDel_addAF	Pathogenic	0.57	D
BayesDel_noAF	Pathogenic	0.60
CADD	Pathogenic	27
DANN	Benign	0.90
DEOGEN2	Pathogenic	0.99	D;.;D
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.99
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	1.0	D;D;D
M_CAP	Pathogenic	0.36	D
MetaRNN	Pathogenic	0.98	D;D;D
MetaSVM	Pathogenic	0.99	D
MutationAssessor	Pathogenic	4.5	H;.;.
MutationTaster	Benign	1.0	A;A;A;A;A
PrimateAI	Uncertain	0.61	T
PROVEAN	Pathogenic	-5.8	D;D;D
REVEL	Pathogenic	0.99
Sift	Pathogenic	0.0	D;D;D
Sift4G	Pathogenic	0.0	D;D;D
Polyphen		1.0	D;.;.
Vest4		0.99
MVP		1.0
MPC		0.82
ClinPred		0.99	D
GERP RS		5.8
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.99
gMVP		0.99

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

Publications

LitVar

Other links and lift over

dbSNP: rs121907973; hg19: chr15-72643556;