GBA1MUTATIONS ALTER THE PHENOTYPE AND BEHAVIOUR OF DOPAMINERGIC NEURONS IN PARKINSON’S DISEASE, INFLUENCINGVGLUT2ANDCRYABEXPRESSION

Abstract

ABSTRACTMutations in theglucocerebrosidase 1(GBA1) gene, encoding a lysosomal enzyme, are major risk factors for Parkinsońs disease (PD). The impact ofGBA1mutations on neuronal maturation, function and degeneration was investigated in dopaminergic (DA) neurons obtained from our repository of induced pluripotent stem cells (iPS cells or iPSCs), cells derived from PD patients carrying the heterozygous N370S or L444P mutation inGBA1, or from healthy subjects (controls). DA neurons co-expressing TH and VGLUT2 were detected in the cultures, and their number and/or expression ofSLC17A6/VGLUT2mRNA was markedly reduced in both N370S and L444P cultures. Electrophysiological recordings revealed a significant increase in the firing rate of N370S but not L444P neurons, whereas evoked dopamine release was stronger from neurons carrying either mutation than from the controls. Remarkably, neurons carrying eitherGBA1mutation accumulated abundant degenerative bodies, multilamellar bodies, autophagosomes and Golgi apparatus vacuolated dictyosomes, with some differences in neurons carrying the N370S or L444P mutation. Furthermore, there was a significant accumulation of α-synuclein aggregates in the cell body and dendrites of N370S neurons. Notably, a significant upregulation of the small chaperoneCRYAB(HSPB5/alpha-crystallin-B) was found early in DA neuron differentiation and in the Substantia Nigra of PD patients. Our findings indicate that N370S and L444PGBA1mutations produce some similar and other distinct molecular, electrical and ultrastructural alterations in DA neurons. They suggest that these mutations impair the VGLUT2 subpopulation of midbrain DA neurons, and provoke stress responses early in the neuronal differentiation programme.