Single cell analysis of iPSC-derived midbrain organoids (GBA1 mutant and controls)
Ontology highlight
ABSTRACT: Mutations in the lysosomal enzyme β-glucocerebrosidase (GCase), which cause Gaucher´s disease, are the most frequent genetic risk factor for Parkinson’s disease (PD). Here, we employed single-cell genomic approaches in induced pluripotent stem cell (iPSC)-derived midbrain organoids to dissect the mechanisms underlying GCase-related neurodegeneration.
Project description:The GBA1 gene encodes the lysosomal enzyme acid-β-glucocerebrosidase (GCase). GBA1 mutations cause the lysosomal storage disorder Gaucher disease (GD) and are a genetic risk factor for Parkinson´s disease (PD). Many GBA1 mutations cause aberrant GCase folding and processing but how these impinge on PD pathogenesis remains unclear. We addressed GCase functions in human dopaminergic (DA) neurons derived from engineered GBA1-deficient (GBA1-/-) embryonic stem cells (hESCs) and GBA1N370S PD patient-derived induced pluripotent cells (hiPSCs). GBA1-mutant DA neurons displayed aberrant morphologies and gene expression that were rescued by recombinant GCase treatment. GBA1-/- neurons have hyperactive Calcineurin (CaN) and nuclear localization of the Transcription Factor EB (TFEB). Expression of TFEB targets and lysosomal CLEAR network components were increased in GBA1-/- DA neurons and rescued by GCase replacement and CaN inhibition. Our findings reveal a link between increased CaN activity and loss of GCase, providing a mechanism for the disturbed lysosomal/autophagy pathways in GBA1-associated PD.
Project description:Parkinson’s disease (PD) is a prevalent neurodegenerative disorder that is characterized by the selective loss of midbrain dopamine (DA)-producing neurons and the formation of α-synuclein (α-syn)-containing inclusions named Lewy bodies (LBs). Here, we report that the loss of glucocerebrosidase (GCase), coupled with α-syn overexpression, result in substantial accumulation of detergent-resistant α-syn aggregates and Lewy body-like inclusions (LBLIs) in human midbrain-like organoids (hMLOs). These LBLIs exhibit a highly similar structure to PD-associated LBs, by displaying a spherically symmetric morphology with an eosinophilic core, and containing α-syn and ubiquitin. Importantly, hMLOs generated from PD patient-derived inducible pluripotent stem cells (iPSCs) harboring SNCA triplication also exhibit subsequent degeneration of DA neurons and LBLI formation upon chronic GCase inhibitor treatment. Taken together, our hMLOs harbouring two major PD risk factors (GCase deficiency and overproduced α-syn) successfully recapitulate major pathophysiological signatures of the disease, and highlight the broad utility of brain organoid technology in modeling human neurodegenerative diseases.
Project description:Gaucher disease (GD) is an autosomal recessive disorder caused by bi-allelic GBA1 mutations that reduce the activity of the lysosomal enzyme β-glucocerebrosidase (GCase). In the immune system, GCase deficiency deregulates signal transduction events, resulting in an inflammatory environment. It is known that the complement system promotes inflammation, and complement inhibitors are currently being considered as a novel therapy for GD; however, the mechanism by which complement drives ystemic macrophage-mediated inflammation remains incompletely understood. To help understand the mechanisms involved, we performed gene array analysis on rC5a-treated human control and GD-induced pluripotent stem cell (iPSC)-derived macrophages.
Project description:Mutations in the acid β-glucocerebrosidase (GBA1) gene, responsible for the lysosomal storage disorder Gaucher’s disease (GD), are the strongest genetic risk factor for Parkinson’s disease (PD) known to date. To elucidate the mechanisms underlying neurodegeneration in these patients, we generated induced pluripotent stem cells from subjects with GD and PD harboring GBA1 mutations and differentiated them to midbrain dopaminergic neurons. Highly enriched neurons showed a reduction of glucocerebrosidase activity and protein levels, increased glucosylceramide and α-synuclein levels and autophagic/lysosomal defects. Quantitative proteomics profiling revealed an increase of the neuronal calcium-binding protein 2 (NECAB2) in diseased neurons. We found dysregulation of calcium homeostasis and increased vulnerability to stress responses involving elevation of cytosolic calcium in mutant neurons. Importantly, correction of the mutations rescued such pathological phenotypes. Our findings provide evidence for a link between GBA1 mutations and complex changes in autophagic/lysosomal system and intracellular calcium homeostasis, which underlie vulnerability to neurodegeneration.
Project description:The most common genetic risk factors for Parkinson’s disease (PD) are a set of heterozygous mutant (MT) alleles of the GBA1 gene that encodes Beta-glucocerebrosidase (GCase), an enzyme normally trafficked through the ER/ Golgi apparatus to the lysosomal lumen. We found that half of the GCase in lysosomes from post-mortem human GBA-PD brains was present on the lysosomal surface, and that this mislocalization depends on a pentapeptide motif in GCase used to target cytosolic protein for degradation by chaperone-mediated autophagy (CMA). Unfolded mutant GCase at the lysosomal surface inhibits CMA, causing accumulation of CMA substrates including -synuclein. Using single cell transcriptional analysis and comparative proteomics of brains from GBA-PD patients we confirmed reduced CMA activity and proteome changes comparable to those in CMA-deficient mouse brain. Loss of the MT GCase CMA motif is sufficient to rescue primary substantia nigra dopamine neurons from MT-GCase induced neuronal death. We conclude that MT GCase alleles block CMA function and produce -synuclein accumulation.
Project description:Lysosomal degradation pathways coordinate the clearance of superfluous and damaged cellular components. Compromised lysosomal degradation is a hallmark of many degenerative diseases, including lysosomal storage diseases, which are caused by loss-of-function mutations within both alleles of a lysosomal hydrolase, leading to lysosomal substrate accumulation. Gaucher’s disease, characterized by <15% of normal glucocerebrosidase function, is the most common lysosomal storage disease and is a prominent risk factor for developing Parkinson’s disease. Here, we show that either of two structurally distinct small molecules that modulate PIKfyve activity, discovered from a high-throughput cellular lipid droplet clearance screen, can improve glucocerebrosidase function in Gaucher patient–derived fibroblasts through an MiT/TFE transcription factor that promotes lysosomal gene translation. An ISR antagonist used in combination with a PIKfyve modulator further improves cellular glucocerebrosidase activity, likely because integrated stress response (ISR) signaling appears to also be slightly activated by treatment by either small molecule at the higher doses employed, This strategy of combining a PIKfyve modulator with an integrated stress response inhibitor improves mutant lysosomal hydrolase function in cellular models of additional lysosomal storage diseases.
Project description:Heterozygous mutations in the glucocerebrosidase gene (GBA) are the strongest common genetic risk factors for Parkinson’s disease (PD) present in around 5-10% of PD patients, resulting in lower age of onset and exacerbating disease progression, including an increased risk of dementia. However, the exact mechanisms leading from dysfunction of the enzyme glucocerebrosidase (GCase) encoded by GBA to PD pathogenesis and neurodegeneration remain unclear. Applying a novel multi-part enrichment workflow we have developed, we have isolated and quantified peptides with phosphorylation, cysteine-modification or N-linked glycosylation simultaneously. We applied this methodology to iPSC-derived dopaminergic neurons from GBA-N370S PD patients and healthy age-matched controls, identifying large numbers of dysregulated native and modified proteins.
Project description:Gaucher disease type 1 is an inborn error of metabolic disease with the defective activity of the lysosomal enzyme acid b-glucosidase (GCase). Enzyme replacement/reconstitution therapy (ERT), infusions with purified recombinant GCases, is efficacious in reversing hematologic, hepatic, splenic, and bony disease manifestations in Gaucher type 1 patients. However, the tissue specific molecular events in Gaucher disease and their response to therapy are not known yet. To explore the molecular events underlying GCase treatment, we evaluated the tissue-specific gene expression profiles and molecular responses in our Gaucher disease mouse model, which were treated with two FDA approved commercially available GCases, imiglucerase (imig) and velaglucerase alfa (vela). Using microarray and mRNA-Seq techniques, differentially expressed genes (DEGs) were identified in the spleen and liver by the direct comparison of imig- vs. vela- treated mice. Among them three gene expression networks were derived from these spleens: 1) cell division/proliferation, 2) hematopoietic system and 3) inflammatory/macrophage response. Our study showed the occurrence of differential molecular pathophysiologic processes in the mice treated with imig compared with vela even though these two biosimilars had the same histological and biochemical efficacy 9V/null mice (Gaucher mouse model) were injected weekly via tail vein with 60U/kg/wk of imig or vela for 8 wks. To understand the molecular events underlying GCase treatment, we evaluated the tissue-specific gene expression profiles and molecular responses in our Gaucher disease mouse model, which were treated with two FDA approved commercially available GCases, imiglucerase (imig) and velaglucerase alfa (vela).
Project description:Gaucher Disease (GD) is caused by defective glucocerebrosidase (GCase) activity and the consequent accumulation of its substrate, glucosylceramide (GC). This excess of accumulation of GC leads to broad functional impairments in multiple organs, but the pathogenic pathways leading to lipid laden macrophages (Gaucher cells) in visceral organs and their abnormal function is obscure. To understand the molecular pathogenesis of GD, developmental global gene expression was conducted by microarray analyses of total mRNAs from lung and liver of two distinct GCase point-mutated mice (V394L/V394L and D409V/null) and genetic background matched wild-type controls. INFg regulated pro-inflammatory and IL-4 regulated anti-inflammatory cytokine/mediator network were constructed in the lung and liver of GCase mutant mice. Progressive alterations of the INFg and IL-4 pathways were similar, but to different degrees, in visceral tissues from the two different GCase mutated mice. These analyses implicate IFNg regulated pro-inflammatory and IL-4 regulated anti-inflammatory networks in the differential pathophysiological progression.
Project description:Gaucher disease type 1 is an inborn error of metabolic disease with the defective activity of the lysosomal enzyme acid b-glucosidase (GCase). Enzyme replacement/reconstitution therapy (ERT), infusions with purified recombinant GCases, is efficacious in reversing hematologic, hepatic, splenic, and bony disease manifestations in Gaucher type 1 patients. However, the tissue specific molecular events in Gaucher disease and their response to therapy are not known yet. To explore the molecular events underlying GCase treatment, we evaluated the tissue-specific gene expression profiles and molecular responses in our Gaucher disease mouse model, which were treated with two FDA approved commercially available GCases, imiglucerase (imig) and velaglucerase alfa (vela). Using microarray and mRNA-Seq techniques, differentially expressed genes (DEGs) were identified in the spleen and liver by the direct comparison of imig- vs. vela-treated mice. Among them three gene expression networks were derived from these spleens: 1) cell division/proliferation, 2) hematopoietic system and 3) inflammatory/macrophage response. Our study showed the occurrence of differential molecular pathophysiologic processes in the mice treated with imig compared with vela even though these two biosimilars had the same histological and biochemical efficacy 9V/null mice (Gaucher mouse model) were injected weekly via tail vein with 60U/kg/wk of imig or vela for 8 wks and were sacrificed one week after the injection for RNA isolation from different tissues like liver, lung and spleen.