3-32997049-A-C

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 2P and 4B. PM2 BP4_Strong

The NM_000404.4(GLB1):c.2030T>G(p.Val677Gly) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000991 in 1,613,940 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 15/19 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Synonymous variant affecting the same amino acid position (i.e. V677V) has been classified as Likely benign.

• Frequency:
  • Genomes: 𝑓 0.000020 (0 hom., cov: 32)
  • Exomes 𝑓: 0.0000089 (0 hom.)
• Consequence: GLB1 NM_000404.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter P:1 U:1
• Conservation: PhyloP100: -0.567

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_benign. Variant got -2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.05303365).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GLB1	NM_000404.4	c.2030T>G	p.Val677Gly	missense_variant	16/16	ENST00000307363.10

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GLB1	ENST00000307363.10	c.2030T>G	p.Val677Gly	missense_variant	16/16	1	NM_000404.4	P2
GLB1	ENST00000307377.12	c.1637T>G	p.Val546Gly	missense_variant	13/13	1
GLB1	ENST00000399402.7	c.1940T>G	p.Val647Gly	missense_variant	16/16	2		A2

Frequencies

GnomAD3 genomes AF: 0.0000197 AC: 3 AN: 152058 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000131

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000147

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.00000802 AC: 2 AN: 249468 Hom.: 0 AF XY: 0.00000739 AC XY: 1 AN XY: 135346

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000290

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: 0.00000883

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000889 AC: 13 AN: 1461882 Hom.: 0 Cov.: 31 AF XY: 0.00000550 AC XY: 4 AN XY: 727240

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000447

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: 0.00000809

Gnomad4 OTH exome AF: 0.0000331

GnomAD4 genome AF: 0.0000197 AC: 3 AN: 152058 Hom.: 0 Cov.: 32 AF XY: 0.0000135 AC XY: 1 AN XY: 74270

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.000131

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.0000147

Gnomad4 OTH AF: 0.00

Alfa AF: 0.0000329 Hom.: 0

Bravo AF: 0.0000378

ExAC AF: 0.0000165 AC: 2

ClinVar

Significance: Uncertain significance

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Mucopolysaccharidosis, MPS-IV-B Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

OMIM

May 12, 2021

- -

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

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Aug 16, 2022

This sequence change replaces valine, which is neutral and non-polar, with glycine, which is neutral and non-polar, at codon 677 of the GLB1 protein (p.Val677Gly). This variant is present in population databases (rs767685019, gnomAD 0.003%). This missense change has been observed in individual(s) with GLB1-related conditions (PMID: 33558080; Invitae). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. ClinVar contains an entry for this variant (Variation ID: 968996). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is not expected to disrupt GLB1 protein function. 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	0.083
BayesDel_addAF	Benign	-0.047	T
BayesDel_noAF	Benign	-0.22
Cadd	Benign	0.92
Dann	Benign	0.96
Eigen	Benign	-1.6
Eigen_PC	Benign	-1.7
FATHMM_MKL	Benign	0.029	N
M_CAP	Benign	0.083	D
MetaRNN	Benign	0.053	T;T;T
MetaSVM	Uncertain	-0.21	T
MutationTaster	Benign	1.0	N;N;N;N
PrimateAI	Benign	0.33	T
PROVEAN	Benign	-0.68	N;N;N
REVEL	Benign	0.18
Sift	Uncertain	0.0050	D;D;D
Sift4G	Uncertain	0.0070	D;D;D
Polyphen		0.0	.;.;B
Vest4		0.047
MutPred		0.26		Loss of stability (P = 0);.;.;
MVP		0.30
MPC		0.31
ClinPred		0.047	T
GERP RS		-8.0
gMVP		0.64

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: rs767685019; hg19: chr3-33038541;