Decreased glucocerebrosidase activity and substrate accumulation of glycosphingolipids in a novel GBA1 D409V knock-in mouse model

Abstract

Multiple mutations have been described in the human GBA1 gene, which encodes the lysosomal enzyme beta-glucocerebrosidase (GCase) that degrades glucosylceramide and is pivotal in glycosphingolipid substrate metabolism. Depletion of GCase, typically by homozygous mutations in GBA1, is linked to the lysosomal storage disorder Gaucher’s disease (GD) and distinct or heterozygous mutations in GBA1 are associated with increased Parkinson’s disease (PD) risk. While numerous genes have been linked to heritable PD, GBA1 mutations in aggregate are the single greatest risk factor for development of idiopathic PD. The importance of GCase in PD necessitates preclinical models in which to study GCase-related mechanisms and novel therapeutic approaches, as well as to elucidate the molecular mechanisms leading to enhanced PD risk in GBA1 mutation carriers. The aim of this study was to develop and characterize a novel GBA1 mouse model and to facilitate wide accessibility of the model with phenotypic data. Herein we describe the results of molecular, biochemical, histological, and behavioral phenotyping analyses in a GBA1 D409V knock-in (KI) mouse. This mouse model exhibited significantly decreased GCase activity in liver and brain, with substantial increases in glycosphingolipid substrates in the liver. While no changes in the number of dopamine neurons in the substantia nigra were noted, subtle changes in striatal neurotransmitters were observed in GBA1 D409V KI mice. Alpha-synuclein pathology and inflammation were not observed in the nigrostriatal system of this model. In summary, the GBA1 D409V KI mouse model provides an ideal model for studies aimed at pharmacodynamic assessments of potential therapies aiming to restore GCase.

Neuronopathic GBA1 L444P mutation accelerates Glucosylsphingosine levels and formation of hippocampal alpha-synuclein inclusions

“…Here, we show reduced GCase activity in the cortex, striatum, hippocampus, and midbrain of GBA1 +/L444P knock-in mice relative to wildtype (GBA1 +/+ ) mice. GBA1 +/L444P mice and aged GBA1 +/+ mice show increased brain levels of glucosylsphingosine, but not glucosylceramide which is consistent with previous findings (Taguchi et al, 2016; Polinski et al, 2021). GBA1 +/L444P mice also show reduced levels of the presynaptic protein, vGLUT1, and impairments in fear conditioning, but not motor behavior, suggesting that mutant GBA1 alone causes neuronal defects in limbic brain regions.…”

“…Interestingly, the heterozygous L444P mutation reduced GCase activity by 21.6-31.9% depending on the brain region evaluated. In contrast, the homozygous D409V mutation had a significantly greater reduction of GCase activity (Polinski et al, 2021). While the reduction of GCase activity may not be associated with PD risk or severity, it may contribute to the efficacy of GCS inhibition through other mechanisms (Omer et al, 2022).…”

Genetically engineered microglia-like cells have therapeutic potential for neurodegenerative disease

“…Mutations in GBA are causative for the lysosomal storage disorder Gaucher disease and are among the most prevalent genetic risk factors for Parkinson's disease 36,37 and Lewy body dementia 38 . To assess the utility of lentiviral HSPC-GT for Parkinson's disease patients associated with a GBA mutation (GBA-PD), we conducted a biodistribution study of key organs in homozygous Gba D409V mice, a model of GBA-PD 39 . We isolated lineage negative cells and transduced them with either a lentiviral vector encoding our previously characterized human GBA transgene (LVV.GBA) or a control GFP transgene (LVV.GFP) at similar number of vector integrations (LVV.GBA: 3.12  0.15, LVV.GFP: 2.93  0.14; Fig.…”

“…Comparisons of intravenous (IV) and intracerebroventricular (ICV) routes of administration were completed using wild-type (WT) C57BL/6J mice (Jackson Laboratory, stock number 000664). Proof of concept experiments for GBA-Parkinson's Disease (GBA-PD) were completed using homozygous Gba D409V/D409V mutant mice (Jackson Laboratory, C57BL/6N-Gba tm1.1Mjff /J, stock number 019106) 39 and wild-type C57BL/6NJ mice (Jackson Laboratory, stock number 005304) as controls. Proof of concept experiments for progranulin-associated frontotemporal dementia (GRN-FTD) were completed using heterozygous and homozygous Grn R493X mutant mice on the C57BL/6J background .…”

The GBA1 D409V mutation exacerbates synuclein pathology to differing extents in two alpha-synuclein models

“…These models generally feature knockout of the GBA1 gene ( Xu et al, 2003 ; Enquist et al, 2007 ; Sardi et al, 2011 ), treatment with the GCase inhibitor conduritol β-epoxide (CBE; Manning-Boğ et al, 2009 ; Rocha et al, 2015 ) or mutations in the GBA1 gene ( Liu et al, 1998 ; Xu et al, 2003 ; Sardi et al, 2011 ; Cullen et al, 2011 ; Ginns et al, 2014 ). Even though most of these models exhibit dramatic reductions in GCase activity, many do not display nigrostriatal degeneration or PD-related motor symptoms ( Farfel-Becker et al, 2019 ; Migdalska-Richards et al, 2017 ; Xu et al, 2003 , 2011 ; Polinski et al, 2021 ; Sardi et al, 2011 ; Rocha et al, 2015 ). Importantly, the presence of a mutation in the GBA1 gene is not uniformly causal for developing PD.…”