Biology subjects

Di Monte, D. A.

Publications and source records attributed to Di Monte, D. A..

3 recordsLinked to original sources

bioRxiv2021

Inhibition of microglial GBA hampers the microglia-mediated anti-oxidant and protective response in neurons

Homozygotic mutations in the GBA gene cause Gauchers disease, moreover, both patients and heterozygotic carriers have been associated with 20- to 30-fold increased risk of developing Parkinsons disease. In homozygosis, these mutations impair the activity of {beta}-glucocerebrosidase, the enzyme encoded by GBA, and generate a lysosomal disorder in macrophages, which changes morphology towards an engorged phenotype, considered the hallmark of Gauchers disease. In the brain, most of the pathological effects caused by GBA mutations have been attributed to the {beta}-glucocerebrosidase deficit in neurons, while a microglial phenotype for these mutations has never been reported. Here, we applied the bioluminescence imaging technology, immunohistochemical and gene expression analysis to investigate the consequences of microglial {beta}-glucocerebrosidase inhibition in the brain of reporter mice, in primary neuron/microglia co-cultures and in cell lines. Our data demonstrate the existence of a novel mechanism by which microglia sustain the antioxidant/detoxifying response mediated by the nuclear factor erythroid 2-related factor 2 in neurons. The central role played by microglia in this neuronal response in vivo was proven by pharmacological depletion of the lineage in the brain, while co-cultures experiments provided insight on the nature of this cell-to-cell communication showing that this mechanism requires a direct microglia-to-neuron contact supported by functional actin structures. Pharmacological inhibition of microglial {beta}-glucocerebrosidase was proven to induce morphological changes, turn on an anti-inflammatory/repairing pathway and hinder the microglia ability to activate the anti-oxidant/detoxifying response, thus increasing the neuronal susceptibility to neurotoxins. Altogether, our data suggest that microglial {beta}-glucocerebrosidase inhibition impairs microglia-to-neuron communication increasing the sensitivity of neurons to oxidative or toxic insults, thus providing a possible mechanism for the increased risk of neurodegeneration observed in carriers of GBA mutations. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=154 SRC="FIGDIR/small/427380v1_ufig1.gif" ALT="Figure 1"> View larger version (60K): org.highwire.dtl.DTLVardef@15c2c3corg.highwire.dtl.DTLVardef@5c4e34org.highwire.dtl.DTLVardef@12718dorg.highwire.dtl.DTLVardef@dcfeca_HPS_FORMAT_FIGEXP M_FIG C_FIG In BriefMicroglia, through actin-dependent structures, contact neurons and induce a detoxification response by increasing the NFE2L2 signalling pathway. Inhibition of GCase activity by CBE treatment produces a morpho-functional change in microglia cells hampering the neuroprotective microglia-neuron communication thus inducing a phenotype in dopaminergic neurons characterized by increased susceptibility to oxidative stress or toxic insults.

neuroscience↗

bioRxiv2020

Sphingolipid changes in Parkinson L444P GBA mutation fibroblasts promote α-synuclein aggregation

Intraneuronal accumulation of aggregated -synuclein is a pathological hallmark of Parkinsons disease. Therefore, mechanisms capable of promoting -synuclein deposition bear important pathogenetic implications. Mutations of the glucocerebrosidase 1 (GBA) gene represent a prevalent Parkinsons disease risk factor. They are associated with loss of activity of a key enzyme involved in lipid metabolism, glucocerebrosidase, supporting a mechanistic relationship between abnormal -synuclein-lipid interactions and the development of Parkinson pathology. In this study, the lipid membrane composition of fibroblasts isolated from control subjects, patients with idiopathic Parkinsons disease (iPD) and Parkinson patients carrying the L444P GBA mutation (PD-GBA) was assayed using shotgun lipidomics. The lipid profile of PD-GBA fibroblasts differed significantly from that of control and iPD cells. It was characterized by an overall increase in sphingolipid levels. It also featured a significant change in the proportion of ceramide, sphingomyelin and hexosylceramide molecules with shorter and longer hydrocarbon chain length; levels of shorter-chain molecules were increased while the percent of longer-chain sphingolipids was decreased in PD-GBA lipid extracts. The extent of this shift was correlated to the degree of reduction of fibroblast glucocerebrosidase activity. In a second set of experiments, lipid extracts from control and PD-GBA fibroblasts were added to incubations of recombinant -synuclein. The kinetics of -synuclein aggregation, as assessed by the binding of thioflavin T to amyloid structures, was significantly accelerated after addition of PD-GBA extracts as compared to control samples. Amyloid fibrils collected at the end of these incubations contained lipids, indicating -synuclein-lipid co-assembly. Lipids extracted from -synuclein fibrils were also analysed by shotgun lipidomics. Data revealed that the lipid content of these fibrils was significantly enriched of shorter-chain sphingolipids. Taken together, findings of this study indicate that the L444P GBA mutation and consequent enzymatic loss are associated with a distinctly altered membrane lipid profile that provides a biological fingerprint of this mutation in Parkinson fibroblasts. This altered lipid profile, which includes an increased content of shorter-chain sphingolipids, could also be an indicator of increased risk for -synuclein aggregate pathology. Shorter-chain molecules may act as preferred reactants during lipid-induced -synuclein fibrillation.

biochemistry↗

bioRxiv2020

The transcription factor BCL11A defines a distinctive subset of dopamine neurons in the developing and adult midbrain

Midbrain dopaminergic (mDA) neurons are diverse in their projection targets, impact on behavior and susceptibility to neurodegeneration. Little is known about the molecular mechanisms that establish this diversity in mDA neurons during development. We find that the transcription factor Bcl11a defines a subset of mDA neurons in the developing and adult murine brain. By combining intersectional labeling and viral-mediated tracing we show that Bcl11a-expressing mDA neurons form a highly specific subcircuit within the dopaminergic system. We demonstrate that Bcl11a-expressing mDA neurons in the substantia nigra (SN) are particularly vulnerable to neurodegeneration in an -synuclein overexpression model of Parkinsons disease. Inactivation of Bcl11a in developing mDA neurons results in anatomical changes, deficits in motor learning and a dramatic increase in the susceptibility to -synuclein-induced degeneration in SN-mDA neurons. In summary, we identify an mDA subpopulation with highly distinctive characteristics defined by the expression of the transcription factor Bcl11a already during development.

developmental biology↗