chr15-72350578-G-A

Position:

• chr15-72350578-G-A

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM1 PM2 PP3_Moderate

The NM_000520.6(HEXA):​c.745C>T​(p.Arg249Trp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000274 in 1,614,120 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,other (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R249Q) has been classified as Uncertain significance.

• Frequency:
  • Genomes: 𝑓 0.00020 (0 hom., cov: 32)
  • Exomes 𝑓: 0.00028 (0 hom.)
• Consequence: HEXA NM_000520.6 missense
• Clinical Significance: Conflicting classifications of pathogenicity; other criteria provided, conflicting classifications U:1 B:1 O:3
• Conservation: PhyloP100: 2.11

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 6 ACMG points.

• PM1: In a hotspot region, there are 4 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 5 uncertain in NM_000520.6
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.927

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
HEXA	NM_000520.6	c.745C>T	p.Arg249Trp	missense_variant	7/14	ENST00000268097.10
HEXA	NM_001318825.2	c.778C>T	p.Arg260Trp	missense_variant	7/14
HEXA	NR_134869.3	n.787C>T		non_coding_transcript_exon_variant	7/11

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
HEXA	ENST00000268097.10	c.745C>T	p.Arg249Trp	missense_variant	7/14	1	NM_000520.6	P1
	ENST00000570175.1	n.1932G>A		non_coding_transcript_exon_variant	3/3	1

Frequencies

GnomAD3 genomes AF: 0.000204 AC: 31 AN: 152174 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.000121

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00135

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.000279

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.000191 AC: 48 AN: 251478 Hom.: 0 AF XY: 0.000199 AC XY: 27 AN XY: 135910

Gnomad AFR exome AF: 0.000123

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.000707

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.000290

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.000282 AC: 412 AN: 1461828 Hom.: 0 Cov.: 31 AF XY: 0.000272 AC XY: 198 AN XY: 727218

Gnomad4 AFR exome AF: 0.000149

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.000579

Gnomad4 SAS exome AF: 0.0000348

Gnomad4 FIN exome AF: 0.0000187

Gnomad4 NFE exome AF: 0.000304

Gnomad4 OTH exome AF: 0.000696

GnomAD4 genome AF: 0.000204 AC: 31 AN: 152292 Hom.: 0 Cov.: 32 AF XY: 0.000188 AC XY: 14 AN XY: 74482

Gnomad4 AFR AF: 0.000120

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00135

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.000279

Gnomad4 OTH AF: 0.00

Alfa AF: 0.000333 Hom.: 1

Bravo AF: 0.000246

TwinsUK AF: 0.000270 AC: 1

ALSPAC AF: 0.00 AC: 0

ESP6500AA AF: 0.00 AC: 0

ESP6500EA AF: 0.000582 AC: 5

ExAC AF: 0.000231 AC: 28

Asia WGS AF: 0.000577 AC: 2 AN: 3478

EpiCase AF: 0.000600

EpiControl AF: 0.0000593

ClinVar

Significance: Conflicting classifications of pathogenicity; other

Submissions summary: Uncertain:1 Benign:1 Other:3

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Uncertain:1 Benign:1 Other:1

Uncertain significance, criteria provided, single submitter	clinical testing	CeGaT Center for Human Genetics Tuebingen	Feb 01, 2024	HEXA: PM2:Supporting -
Benign, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Aug 11, 2016	Variant summary: The HEXA c.745C>T (p.Arg249Trp) variant causes a missense change involving a conserved nucleotide with 5/5 in silico tools predicting a damaging outcome. The variant of interest was found in the large, broad control population, ExAC, with an allele frequency of 28/121408 (1/4336), which does not exceed the estimated maximal expected allele frequency for a pathogenic HEXA variant of 1/715. The variant of interest is known to be a common pseudodeficiency allele, which is not associated with neurologic disease but is associated wtih reduced degradation of the synthetic substrate when HEX A enzymatic activity is determined (Gene Reviews). Therefore, the variant of interest is classified as Benign. -
other, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Jul 19, 2016	- Variant classified as "other reportable" ??? variant is clinically benign (not associated with disease) but is reported when observed (e.g. pseudodeficiency alleles).

Tay-Sachs disease Other:2

other, criteria provided, single submitter	clinical testing	Laboratory for Molecular Medicine, Mass General Brigham Personalized Medicine	May 30, 2014	pseudodeficiency The Arg249Trp variant in HEXA is a well-established pseudodeficiency allele for HEXA activity (Cao 1993) and has been identified in 0.05% (5/8594) of European American chromosomes by the NHLBI Exome Sequencing Project (http://evs.gs.washington.edu/EVS/; dbSNP rs138058578). The Arg249Trp variant is clinically benign (i.e., has normal activity in vivo) but has reduced HEXA enzyme activity toward synthetic substrates and therefore can produce a false positive result on enzyme analysis, a technique often used for carrier screening (Hoffman 2013).
other, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Dec 13, 2018	- pseudodeficiency allele

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.40
BayesDel_addAF	Pathogenic	0.28	D
BayesDel_noAF	Pathogenic	0.53
CADD	Pathogenic	29
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.98	D;.;D
Eigen	Uncertain	0.65
Eigen_PC	Uncertain	0.55
FATHMM_MKL	Uncertain	0.94	D
LIST_S2	Uncertain	0.96	D;D;D
M_CAP	Uncertain	0.25	D
MetaRNN	Pathogenic	0.93	D;D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.9	H;.;.
MutationTaster	Benign	1.0	D;D;D;D;D
PrimateAI	Uncertain	0.64	T
PROVEAN	Pathogenic	-7.8	D;D;D
REVEL	Pathogenic	0.93
Sift	Pathogenic	0.0	D;D;D
Sift4G	Pathogenic	0.0	D;D;D
Polyphen		1.0	D;.;.
Vest4		0.88
MVP		1.0
MPC		0.73
ClinPred		0.95	D
GERP RS		5.0
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.92
gMVP		0.97

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		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: rs138058578; hg19: chr15-72642919; COSMIC: COSV99173798; COSMIC: COSV99173798;