Abstract

Background: Gaucher disease, the most predominant Lysosomal Storage Disease, is caused by the defective activity of lysosomal acid--glucosidase (glucocerebrosidase, GBA), resulting in accumulation of the glycosphingolipid, glucosylceramide (GlcCer). The disease can be divided into 3 major subtypes: type 1, which presents with hepatosplenomegaly and bone disease, and types 2 and 3, which result in severe neurological disorders in patients. Nearly 200 mutations in GBA have been described, but for most part, a definitive correlation between genotype and phenotype does not exist. Indeed, the same mutation leads to completely different clinical manifestations, indicating that there are “modifiers of disease progression”. Little is known about the down-stream biochemical changes that occur upon GlcCer accumulation that result in cell and tissue dysfunction in different types of GD. Specific Aim 1: Generate novel mouse models of different subtypes of GD. We already have generated new mouse models for each subtype of GD by daily injection of the GBA inhibitor Conduritol B Epoxide (CBE) to 14 different mice strains. As in humans, some mouse strains lived for very short periods of time and developed a very aggressive brain disease (mimicking the neuropathic types of GD), while other strains lived for longer times and did not show neurological symptoms. Interestingly, CBE inhibited GBA activity in the brain to the same extent in every strain, and no correlation between lipid levels in the brain and lifespan were found. These results indicate that the susceptibility to develop neuropathic forms of GD are due to intrinsic properties of the tissue, highlighting an important role for modifier genes in disease progression Specific Aim 2: Identify genes that modify GD progression. The Single Nucleotide Polymorphisms (SNPs) profiles of each mouse strain chosen are available on the web. Based on that information, we will perform a Genome Wide Association Study (GWAS) using the parameters described in Aim 1. By bioinformatics tools we will determine whether the associated genes are grouped in common pathways. We will characterize the expression of our candidate genes/pathways in the different CBE-treated mice strains and we will modulate them genetically and/or pharmacologically, depending on the availability of these tools. Specific Aim 3: Validation of the modifier genes in samples of GD patients. In collaboration with Prof. John Hardy (UCL) we will validate the potential modifier genes identified in mice in GD patients with different subtype of disease. For this we will perform Whole-Exome Sequencing in samples of GD with different subtypes. This will be the final demonstration of the predictive potential of the modifiers identified. We expect to conclude our studies in 2 years. The interdisciplinary nature of the project means we will discover genetic modifiers of GD and pathways involved in susceptibility/resistance with potential identification of novel therapeutic targets for each subtype of GD. GD shares common features with other lysosomal diseases and Parkinson Disease so the knowledge generated here could lead to new potential therapeutic strategies for GD, and to applications for other LSDs and neurological diseases.