3-33072618-G-C

Position:

• chr3-33072618-G-C

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000404.4(GLB1):​c.171C>G​(p.Tyr57*) variant causes a stop gained change involving the alteration of a non-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 (★★). Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 32)
• Consequence: GLB1 NM_000404.4 stop_gained
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:6
• Conservation: PhyloP100: 0.640

Genes affected

GLB1 (HGNC:4298): (galactosidase beta 1) This gene encodes a member of the glycosyl hydrolase 35 family of proteins. Alternative splicing results in multiple transcript variants, at least one of which encodes a preproprotein that is proteolytically processed to generate the mature lysosomal enzyme. This enzyme catalyzes the hydrolysis of a terminal beta-linked galactose residue from ganglioside substrates and other glycoconjugates. Mutations in this gene may result in GM1-gangliosidosis and Morquio B syndrome. [provided by RefSeq, Nov 2015]

GLB1 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 3-33072618-G-C is Pathogenic according to our data. Variant chr3-33072618-G-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 92900.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
GLB1	NM_000404.4	c.171C>G	p.Tyr57*	stop_gained	2/16	ENST00000307363.10	NP_000395.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
GLB1	ENST00000307363.10	c.171C>G	p.Tyr57*	stop_gained	2/16	1	NM_000404.4	ENSP00000306920.4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

Bravo AF: 0.00000378

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:6

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Aug 30, 2013	- -
Pathogenic, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	Aug 03, 2021	- -
Pathogenic, no assertion criteria provided	clinical testing	Mayo Clinic Laboratories, Mayo Clinic	Nov 13, 2017	- -

GM1 gangliosidosis Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

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

Jan 30, 2024

Variant summary: GLB1 c.171C>G (p.Tyr57X) results in a premature termination codon, predicted to cause absence of the protein due to nonsense mediated decay, which is a commonly known mechanism for disease. The variant was absent in 249514 control chromosomes. c.171C>G has been reported in the literature at a homozygous state in at-lease one individual affected with infantile form of GM1 Gangliosidosis (Georgiou_2004). These data indicate that the variant may be associated with disease. At least one publication reports experimental evidence evaluating an impact on protein function. The most pronounced variant effect results in absence of the total and mRNA of GLB1 in the cultured fibroblasts in the patient carrying homozygous c.171C>G via Northen blot analysis (Georgiou_2004). The following publication has been ascertained in the context of this evaluation (PMID: 15365997). ClinVar contains an entry for this variant (Variation ID: 92900). Based on the evidence outlined above, the variant was classified as pathogenic. -

GM1 gangliosidosis;C0086652:Mucopolysaccharidosis, MPS-IV-B Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

May 15, 2022

ClinVar contains an entry for this variant (Variation ID: 92900). This premature translational stop signal has been observed in individual(s) with GM1-gangliosidosis (PMID: 15365997). This variant is not present in population databases (gnomAD no frequency). This sequence change creates a premature translational stop signal (p.Tyr57*) in the GLB1 gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in GLB1 are known to be pathogenic (PMID: 18524657). For these reasons, this variant has been classified as Pathogenic. -

Mucopolysaccharidosis, MPS-IV-B;C0268271:Infantile GM1 gangliosidosis;C0268272:GM1 gangliosidosis type 2;C0268273:GM1 gangliosidosis type 3 Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Counsyl

Dec 18, 2017

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.59
CADD	Pathogenic	35
DANN	Uncertain	0.99
Eigen	Benign	0.18
Eigen_PC	Benign	-0.036
FATHMM_MKL	Uncertain	0.92	D
Vest4		0.76
GERP RS		2.0
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.8

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: rs398123350; hg19: chr3-33114110;