Biology subjects

Milstein, G.

Publications and source records attributed to Milstein, G..

4 recordsLinked to original sources

bioRxiv2024

A Drosophila model for mechanistic investigation of tau protein spread

Brain protein aggregates are a hallmark of neurodegenerative disease. Previous work indicates that specific protein components of these aggregates are toxic, including tau in Alzheimers disease and related tauopathies. Increasing evidence also indicates that these toxic proteins traffic between cells in a prion-like fashion, thereby spreading pathology from one brain region to another. However, the mechanisms involved in trafficking are poorly understood. We therefore developed a transgenic Drosophila model to facilitate rapid evaluation of candidate tau trafficking modifiers. Our model uses the bipartite Q system to drive co-expression of tau and GFP in the fly eye. We find age-dependent tau spread into the brain, represented by detection of tau, but not GFP in the brain. We also found that tau trafficking was attenuated upon inhibition of the endocytic factor dynamin or the kinase glycogen synthase kinase-3{beta} (GSK-3{beta}). Further work revealed that dynamin promotes tau uptake in recipient tissues, whereas GSK-3{beta} appears to promote tau spread via direct phosphorylation of tau. Our robust and flexible system will promote the identification of tau trafficking components involved in the pathogenesis of neurodegenerative diseases. SUMMARY STATEMENTThe trafficking of toxic proteins in neurodegenerative disease is well-known but poorly understood. Our model will allow rapid and new insight into molecular mechanisms underlying this process.

neuroscience↗

bioRxiv2023

Glucocerebrosidase deficiency leads to neuropathology via cellular immune activation

Mutations in GBA (glucosylceramidase beta), which encodes the lysosomal enzyme glucocerebrosidase (GCase), are the strongest genetic risk factor for the neurodegenerative disorders Parkinsons disease (PD) and Lewy body dementia. Recent work has suggested that neuroinflammation may be an important factor in the risk conferred by GBA mutations. We therefore systematically tested the contributions of immune-related genes to neuropathology in a Drosophila model of GCase deficiency. We identified target immune factors via RNA-Seq and proteomics on heads from GCase-deficient flies, which revealed both increased abundance of humoral factors and increased macrophage activation. We then manipulated the identified immune factors and measured their effect on head protein aggregates, a hallmark of neurodegenerative disease. Genetic ablation of humoral (secreted) immune factors did not suppress the development of protein aggregation. By contrast, re-expressing Gba1b in activated macrophages suppressed head protein aggregation in Gba1b mutants and rescued their lifespan and behavioral deficits. Moreover, reducing the GCase substrate glucosylceramide in activated macrophages also ameliorated Gba1b mutant phenotypes. Taken together, our findings show that glucosylceramide accumulation due to GCase deficiency leads to macrophage activation, which in turn promotes the development of neuropathology. Author SummaryMutations in the gene GBA are the largest risk factor for developing Parkinsons disease and Lewy body dementia, diseases in which important brain cells die. We know that the immune system can be involved in these diseases, and that GBA mutations cause immune changes. We did experiments to learn how the immune system changes could make brain cells more likely to die. Using a fruit fly that was missing the fly version of GBA, we found out that inappropriately activated immune cells, but not secreted immune proteins, were important in the development of brain problems. We also learned that the abnormal activation was triggered by the lack of GBA function in the immune cells, not by signals from the brain or other parts of the body. We would like to find out next whether the immune cells get inside the brain or cause harm from a distance. What we learned matters because it could help us prevent or cure brain diseases associated with GBA mutations. Treating the abnormal activation of immune cells in people with these mutations might help prevent damage to the brain.

genetics↗

bioRxiv2020

Glucocerebrosidase reduces the spread of protein aggregation in a Drosophila melanogaster model of neurodegeneration by regulating proteins trafficked by extracellular vesicles

Abnormal protein aggregation within neurons is a key pathologic feature of Parkinsons disease (PD). The spread of protein aggregates in the brain is associated with clinical disease progression, but how this occurs remains unclear. Mutations in the gene glucosidase, beta acid 1 (GBA), which encodes the lysosomal enzyme glucocerebrosidase (GCase), are the most penetrant common genetic risk factor for PD and dementia with Lewy bodies, and also associate with faster disease progression. To explore the mechanism by which mutations in GBA influence pathogenesis of these diseases, we previously created a Drosophila model of GBA deficiency (Gba1b) that manifests neurodegeneration, motor and cognitive deficits, and accelerated protein aggregation. Proteomic analysis of Gba1b mutants revealed dysregulation of proteins involved in extracellular vesicle (EV) biology, and we found altered protein composition of EVs from Gba1b mutants. To further investigate this novel mechanism, we hypothesized that GBA may influence the spread of pathogenic protein aggregates throughout the brain via EVs. We found that protein aggregation is reduced cell-autonomously and non-cell-autonomously by expressing wildtype GCase in specific tissues. In particular, accumulation of insoluble ubiquitinated proteins and Ref(2)P in the brains of Gba1b flies are reduced by ectopic expression of GCase in muscle tissue. Neuronal expression of GCase also cell-autonomously rescued protein aggregation in brain as well as non-cell-autonomously rescued protein aggregation in muscle. Muscle-specific GBA expression rescued the elevated levels of EV-intrinsic proteins and Ref(2)P found in EVs from Gba1b flies. Genetically perturbing EV biogenesis in specific tissues in the absence of GCase revealed differential cell-autonomous effects on protein aggregation but could not replicate the non-cell-autonomous rescue observed with tissue-specific GBA expression. Additionally, we identified ectopically expressed GCase within isolated EVs. Together, our findings suggest that GCase deficiency mediates accelerated spread of protein aggregates between cells and tissues via dysregulated EVs, and EV-mediated trafficking of GCase may partially account for the reduction in aggregate spread. Authors SummaryParkinsons disease (PD) is a common neurodegenerative disease characterized by abnormal clumps of proteins (aggregates) within the brain and other tissues which can lead to cellular dysfunction and death. Mutations in the gene GBA, which encodes glucocerebrosidase (GCase), are the strongest genetic risk factor for PD, and are associated with faster disease progression. GCase-deficient mutant flies display features suggestive of PD including increased protein aggregation in brain and muscle. We found that restoring GCase protein in the muscle of mutant flies reduced protein aggregation in muscle and the brain, suggesting a mechanism involving interaction between tissues. Previous work indicated that GBA influences extracellular vesicles (EVs) - small membrane-bound structures released by cells to communicate and/or transport cargo from cell to cell. Here, we found increased aggregated proteins within EVs of mutant flies, which was reduced by restoring GCase in muscle. In addition, we found GCase within the EVs, possibly explaining how GCase in one tissue such as muscle could reduce protein aggregation in a distant tissue like the brain. Our findings suggest that GCase influences proteins within EVs, affecting the spread of protein aggregation. This may be important to understanding PD progression and could uncover new targets to slow neurodegeneration.

cell biology↗

bioRxiv2018

Montastraea cavernosa corallite structure demonstrates ‘shallow-only’ and ‘depth-generalist’ morphotypes across shallow and mesophotic depth zones in the Gulf of Mexico

This study assessed morphological variation in corallite structure of the depth-generalist coral Montastraea cavernosa across shallow and mesophotic coral ecosystems in the Gulf of Mexico (GOM). Among eight corallite metrics examined, corallite diameters were smaller and spacing was greater in mesophotic corals as compared to shallow corals. Additional corallite variation, including greater corallite height of mesophotic samples, were hypothesized to be photoadaptive responses to low light environments. Although comparison of shallow and mesophotic M. cavernosa was the initial objective of the study, multivariate analyses revealed two distinct morphotypes able to be identified by the significant variation in corallite spacing with >90% accuracy. A shallow-only morphotype was characterized by larger, more closely-spaced corallites, while a depth-generalist type exhibited smaller, further-spaced corallites. The depth-generalist morphotype comprised the majority of mesophotic M. cavernosa colonies sampled from sites in the northwest GOM including the Flower Garden Banks (FGB), Bright Bank, and McGrail Bank. A combination of both morphotypes were found at shallow depths in the FGB. Conversely, in the southeast GOM, the shallow-only morphotype was observed in shallow Dry Tortugas. Mesophotic M. cavernosa at Pulley Ridge were comparable to the shallow-only morphotype in terms of corallite spacing but shared morphological similarities with mesophotic corals for other measured characters, likely representing a hybrid morphology. The variable presence of the morphotypes across sites likely indicates a genotypic influence on corallite morphology, as there was a slight, but significant, impact of morphotype on genetic differentiation within the FGB. Patterns of increased algal symbiont (Symbiodiniaceae) density and chlorophyll concentration were retained in the depth-generalist morphotype even at shallow depths, suggesting multiple photoadaptive strategies between morphotypes. Despite the observed polymorphism in shallow and mesophotic M. cavernosa, the implications for these morphological differences in coral physiology and fitness are not fully known, although some evidence suggests skeletal optical properties may influence bleaching resilience.

ecology↗