rs111840209

Positions:

• chr3-33058199-C-A
• chr3-33058199-C-T

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PM1 PM2 PM5 PP3_Moderate

The NM_000404.4(GLB1):​c.623G>T​(p.Arg208Leu) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,860 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 Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R208C) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: GLB1 NM_000404.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: -0.479

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]

ACMG classification

Verdict is Likely_pathogenic. Variant got 8 ACMG points.

• PM1: In a disulfide_bond (size 35) in uniprot entity BGAL_HUMAN there are 15 pathogenic changes around while only 1 benign (94%) in NM_000404.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chrnull-null-null-null is described in UniProt as null.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.905

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
GLB1	NM_000404.4	c.623G>T	p.Arg208Leu	missense_variant	6/16	ENST00000307363.10	NP_000395.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
GLB1	ENST00000307363.10	c.623G>T	p.Arg208Leu	missense_variant	6/16	1	NM_000404.4	ENSP00000306920	P2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461860 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 727228

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: 8.99e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

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

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jun 29, 2022

This sequence change replaces arginine, which is basic and polar, with leucine, which is neutral and non-polar, at codon 208 of the GLB1 protein (p.Arg208Leu). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with GLB1-related conditions. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Possibly Damaging"; Align-GVGD: "Class C15"). This variant disrupts the p.Arg208 amino acid residue in GLB1. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 8213816, 10338095, 15714521, 17309651, 23337983). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.12
BayesDel_addAF	Uncertain	0.15	D
BayesDel_noAF	Uncertain	-0.030
CADD	Benign	3.3
DANN	Benign	0.96
DEOGEN2	Uncertain	0.67	.;.;D;D
Eigen	Benign	-1.1
Eigen_PC	Benign	-1.4
FATHMM_MKL	Benign	0.41	N
LIST_S2	Benign	0.85	.;.;T;T
M_CAP	Pathogenic	0.61	D
MetaRNN	Pathogenic	0.91	D;D;D;D
MetaSVM	Pathogenic	1.0	D
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Benign	0.25	T
PROVEAN	Pathogenic	-5.7	D;D;D;D
REVEL	Uncertain	0.49
Sift	Uncertain	0.0070	D;D;T;D
Sift4G	Benign	0.067	T;T;T;T
Vest4		0.59
MutPred		0.80		Loss of methylation at R208 (P = 0.0277);.;.;.;
MVP		0.75
MPC		0.63
ClinPred		0.99	D
GERP RS		-8.3
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
gMVP		0.85

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: rs111840209; hg19: chr3-33099691;