Biology subjects

Hirst, W. D.

Publications and source records attributed to Hirst, W. D..

3 recordsLinked to original sources

bioRxiv2025

TFEB and TFE3 have cell-type specific expression in the brain and divergent roles in neurons

Lysosomal dysfunction occurs in many neurodegenerative diseases, including Parkinsons disease, and activating TFEB to enhance lysosomal biogenesis is a promising therapeutic strategy. To understand TFEB physiology in cells of the brain, we characterised TFEB expression using iPSC-derived models, and transcriptomic analysis of human and mouse brain tissue. Surprisingly, TFEB expression at the RNA and protein level was restricted to glia, whereas the related transcription factor, TFE3, was expressed ubiquitously. We identified HDAC1/2/3 as transcriptional repressors of neuronal TFEB and found the brain-penetrant HDAC inhibitor ACY-738 derepressed TFEB expression and enhanced TFE3 nuclear translocation in iPSC-dopaminergic neurons (iPSC-DaNs). We delineated the role of each transcription factor by genetic manipulation in iPSC-DaNs to reveal divergent roles in which TFEB activates mitochondrial biogenesis, whereas TFE3 enhances lysosomal biogenesis. Finally, we show TFE3 activation corrects the lysosomal dysfunction associated with GBA-N370S and SNCA-Triplication mutations in Parkinsons patient-derived iPSC-DaNs, demonstrating therapeutic utility in neurodegeneration.

cell biology↗

bioRxiv2024

ASO-mediated knockdown of GPNMB in mutant-GRN and Grn-deficient peripheral myeloid cells disrupts lysosomal function and immune responses

BackgroundIncreases in GPNMB are detectable in FTD-GRN cerebrospinal fluid (CSF) and post-mortem brain, and brains of aged Grn-deficient mice. Although no upregulation of GPNMB is observed in the brains of young Grn-deficient mice, peripheral immune cells of these mice do exhibit this increase in GPNMB. Importantly, the functional significance of GPNMB upregulation in progranulin-deficient states is currently unknown. Given that GPNMB has been discussed as a potential therapeutic target in GRN-mediated neurodegeneration, it is vital for the field to determine what the normal function of GPNMB is in the immune system, and whether targeting GPNMB will elicit beneficial or deleterious effects. MethodsThe effects of GPNMB knock-down via antisense oligonucleotide (ASO) were assessed in peripheral blood mononuclear cells (PBMCs) from 25 neurologically healthy controls (NHCs) and age- and sex-matched FTD-GRN patients, as well as peritoneal macrophages (pMacs) from progranulin-deficient (Grn-/-) and B6 mice. Lysosomal function, antigen presentation and MHC-II processing and recycling were assessed, as well as cytokine release and transcription. ResultsWe demonstrate here that ASO-mediated knockdown of GPNMB increases lysosomal burden and cytokine secretion in FTD-GRN carrier and neurologically healthy controls (NHCs) monocytes. ASO-mediated knockdown of GPNMB in Grn-deficient macrophages decreased lysosomal pan-cathepsin activity and protein degradation. In addition, ASO-mediated knockdown of GPNMB increased MHC-II surface expression, which was driven by decreased MHC-II uptake and recycling, in macrophages from Grn-deficient females. Finally, ASO-mediated knockdown of GPNMB dysregulated IFN{gamma}-stimulated cytokine transcription and secretion by mouse macrophages due to the absence of regulatory actions of the GPNMB extracellular fragment (ECF). ConclusionsOur data herein reveals that GPNMB has a regulatory effect on multiple immune effector functions, including capping inflammation and immune responses in myeloid cells via secretion of its ECF. Therefore, in progranulin-deficient states, the drastic upregulation in GPNMB transcript and protein may represent a compensatory mechanism to preserve lysosomal function in myeloid cells. These novel findings indicate that targeted depletion in FTD-GRN would not be a rational therapeutic strategy because it is likely to dysregulate important immune cell effector functions.

immunology↗

bioRxiv2022

Is Tau the Initial Pathology in Dopaminergic Nigrostriatal Degeneration? Studies in Parkinsonism and Parkinson ' Disease

While Parkinsons disease (PD) remains clinically defined by cardinal motor symptoms resulting from nigrostriatal degeneration, it is now appreciated that PD consists of multiple pathologies, but it is unclear which occurs first and which are responsible for the nigrostriatal degeneration. For the past number of years, we have been studying a well-characterized cohort of subjects with motor impairment that we have termed mild motor deficits (MMD). Motor deficits were determined on a modified and validated Unified Parkinsons Disease Rating Scale III (UPDRS III), but they occur to a degree insufficient to diagnose PD. We consider this population to have prodromal PD. However, in past studies, cases in this cohort had a selection bias as both a clinical syndrome in between no motor deficits and PD, plus nigral Lewy pathology as defined post-mortem, were required for inclusion. Therefore, in this study, we only based inclusion on a clinical phenotype intermediate between no motor impairment and PD. Then, we divided this group further based upon whether or not they had a synucleinopathy. Here we demonstrate that loss of nigral dopaminergic neurons, loss of putamenal dopaminergic innervation, loss of TH-phenotype in the substantia nigra and putamen, and changes in axonal transport occur equally in groups with and without nigral alpha-synuclein aggregates. Indeed, the common feature of these two groups is that both have similar degrees of AT8-expressing phospho-tau, a pathology not seen in the nigrostriatal system of aged-matched controls. These finding were confirmed with early (CP13) and late (PHF1) tau markers. This suggests that the initiation of nigrostriatal dopaminergic neurodegeneration occurs independently of alpha-synuclein aggregation and is likely tau mediated.

pathology↗