GBA1 inactivation in oligodendrocytes affects myelination and induces neurodegenerative hallmarks and lipid dyshomeostasis in mice

Background Mutations in the beta-glucocerebrosidase (GBA1) gene do cause the lysosomal storage Gaucher disease (GD) and are among the most frequent genetic risk factors for Parkinson's disease (PD). So far, studies on both neuronopathic GD and PD primarily focused on neuronal manifestations, besides the evaluation of microglial and astrocyte implication. White matter alterations were described in the central nervous system of paediatric type 1 GD patients and were suggested to sustain or even play a role in the PD process, although the contribution of oligodendrocytes has been so far scarcely investigated. Methods We exploited a system to study the induction of central myelination in vitro, consisting of Oli-neu cells treated with dibutyryl-cAMP, in order to evaluate the expression levels and function of beta-glucocerebrosidase during oligodendrocyte differentiation. Conduritol-B-epoxide, a beta-glucocerebrosidase irreversible inhibitor was used to dissect the impact of beta-glucocerebrosidase inactivation in the process of myelination, lysosomal degradation and alpha-synuclein accumulation in vitro. Moreover, to study the role of beta-glucocerebrosidase in the white matter in vivo, we developed a novel mouse transgenic line in which beta-glucocerebrosidase function is abolished in myelinating glia, by crossing the Cnp1-cre mouse line with a line bearing loxP sequences flanking Gba1 exons 9-11, encoding for beta-glucocerebrosidase catalytic domain. Immunofluorescence, western blot and lipidomic analyses were performed in brain samples from wild-type and knockout animals in order to assess the impact of genetic inactivation of beta-glucocerebrosidase on myelination and on the onset of early neurodegenerative hallmarks, together with differentiation analysis in primary oligodendrocyte cultures. Results Here we show that beta-glucocerebrosidase inactivation in oligodendrocytes induces lysosomal dysfunction and inhibits myelination in vitro. Moreover, oligodendrocyte-specific beta-glucocerebrosidase loss-of-function was sufficient to induce in vivo demyelination and early neurodegenerative hallmarks, including axonal degeneration, alpha-synuclein accumulation and astrogliosis, together with brain lipid dyshomeostasis and functional impairment. Conclusions Our study sheds light on the contribution of oligodendrocytes in GBA1-related diseases and supports the need for better characterizing oligodendrocytes as actors playing a role in neurodegenerative diseases, also pointing at them as potential novel targets to set a brake to disease progression.