Biology subjects

Magno, L.

Publications and source records attributed to Magno, L..

4 recordsLinked to original sources

bioRxiv2023

The hypermorphic PLCγ2 S707Y variant dysregulates microglial cell function: insight into PLCγ2 activation in brain health and disease, and opportunities for therapeutic modulation.

Phospholipase C-gamma 2 (PLC{gamma}2) is highly expressed in hematopoietic and immune cells, where it is a key signalling node enabling diverse cellular functions. Within the periphery, gain-of-function (GOF) PLC{gamma}2 variants, such as the strongly hypermorphic S707Y, cause severe immune dysregulation. The milder hypermorphic mutation PLC{gamma}2 P522R increases longevity and confers protection in central nervous system (CNS) neurodegenerative disorders, implicating PLC{gamma}2 as a novel therapeutic target for treating these CNS indications. Currently, nothing is known about what consequences strong PLC{gamma}2 GOF has on CNS functionality, and more precisely on the specific biological functions of microglia. Using the PLC{gamma}2 S707Y variant as a model of chronic activation we investigated the functional consequences of strong PLC{gamma}2 GOF on human microglia. PLC{gamma}2 S707Y expressing human inducible pluripotent stem cells (hiPSC)-derived microglia exhibited hypermorphic enzymatic activity under both basal and stimulated conditions, compared to PLC{gamma}2 wild type. Despite the increase in PLC{gamma}2 enzymatic activity, the PLC{gamma}2 S707Y hiPSC-derived microglia display diminished functionality for key microglial processes including phagocytosis and cytokine secretion upon inflammatory challenge. RNA sequencing revealed a downregulation of genes related to innate immunity and response, providing molecular support for the phenotype observed. Our data suggests that chronic activation of PLC{gamma}2 elicits a detrimental phenotype that is contributing to unfavourable CNS functions, and informs on the therapeutic window for targeting PLC{gamma}2 in the CNS. Drug candidates targeting PLC{gamma}2 will need to precisely mimic the effects of the PLC{gamma}2 P522R variant on microglial function, but not those of the PLC{gamma}2 S707Y variant. HighlightsO_LIThe impact of strongly hypermorphic variants of PLC{gamma}2 have not been studied in brain and yet PLC{gamma}2 is implicated in modifying risk of CNS disorders including Alzheimers disease C_LIO_LITo address this, we explored the role of the strongly hypermorphic PLC{gamma}2 S707Y variant in hiPSC-derived microglia C_LIO_LIS707Y increases PLC{gamma}2 enzymatic activity and intracellular calcium flux C_LIO_LIPhagocytosis and cytokine production are diminished in PLC{gamma}2 S707Y microglia C_LIO_LIPLC{gamma}2 S707Y downregulates expression of genes related to innate immunity and response C_LIO_LIModulation of PLC{gamma}2 for therapy must recapitulate the positive effects of moderate hypermorphic variants on microglial functions whilst avoiding detrimental effects of strongly hypermorphic variants like PLC{gamma}2 S707Y C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=188 SRC="FIGDIR/small/564579v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@9f0903org.highwire.dtl.DTLVardef@108d26forg.highwire.dtl.DTLVardef@2fb691org.highwire.dtl.DTLVardef@7af80c_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2022

A primary rodent triculture model to investigate the role of glia-neuron crosstalk in regulation of neuronal activity.

Neuroinflammation and hyperexcitability have been implicated in the pathogenesis of neurodegenerative disease, and new models are required to investigate the cellular crosstalk involved in these processes. We developed an approach to generate a quantitative and reproducible triculture system that is suitable for pharmacological studies. While primary rodent cells were previously grown in a coculture medium formulated to support only neurons and astrocytes, we now optimised a protocol to generate tricultures containing neurons, astrocytes and microglia by culturing in a medium designed to support all three cell types and adding exogenous microglia to cocultures. Immunocytochemistry was used to confirm the intended cell types were present. The percentage of ramified microglia in the tricultures decreases as the number of microglia present increases. Multi-electrode array (MEA) recordings indicate that microglia in the triculture model suppress neuronal activity in a dose-dependent manner. Neurons in both cocultures and tricultures were responsive to the potassium channel blocker 4-aminopyridine (4-AP) suggesting that neurons remained viable and functional in the triculture model. Furthermore, suppressed neuronal activity in tricultures correlated with decreased densities of dendritic spines and of the postsynaptic protein Homer1 along dendrites, indicative of a direct or indirect effect of microglia on synapse function. We thus present a functional triculture model, which, due to its more complete cellular composition, is a more relevant model than standard cocultures. The model can be used to probe glia-neuron interactions and subsequently aid the development of assays for drug discovery, using neuronal excitability as a functional endpoint.

neuroscience↗

bioRxiv2018

Alzheimer’s disease Phospholipase C-gamma-2 (PLCG2) protective variant is a functional hypermorph

Recent Genome Wide Association Studies (GWAS) have identified novel rare coding variants in immune genes associated with late onset AD (LOAD). Amongst these, a polymorphism in Phospholipase C-gamma 2 (PLCG2) P522R, has been reported to be protective against LOAD. PLC enzymes are key elements in signal transmission networks and are potentially druggable targets. PLCG2 is highly expressed in the hematopoietic system. Hypermorphic mutations in PLCG2 in humans have been reported to cause autoinflammation and immune disorders, suggesting a key role for this enzyme in the regulation of immune cell function.\n\nWe confirmed that PLCG2 expression is restricted primarily to microglia in both the healthy and AD brain. Functional analysis of the P522R variant in heterologous systems demonstrated a small hypermorphic effect of the mutation on enzyme function. PLC{gamma}2 is therefore a potential target for modulating microglia function in AD, and a small molecule drug that weakly activates PLC{gamma}2 may be one potential therapeutic approach.\n\nSUMMARYThe PLCG2 P522R variant is protective against Alzheimers disease (AD). We show that PLCG2 is expressed in CNS-resident myeloid cells, and the P522R polymorphism weakly activates enzyme function. These data suggest that activation of PLCG2 and not inhibition could be therapeutically beneficial in AD.

neuroscience↗

bioRxiv2017

Single-Cell Transcriptomic Analysis Of CA1 Inhibitory Neurons

Understanding any brain circuit will require a categorization of its constituent neurons. In hippocampal area CA1, at least 23 classes of GABAergic neuron have been proposed to date. However, this list may be incomplete; additionally, it is unclear whether discrete classes are sufficient to describe the diversity of cortical inhibitory neurons, or whether continuous modes of variability are also required. We studied the transcriptomes of 3663 CA1 inhibitory cells, revealing 10 major GABAergic groups that divided into 49 fine-scale clusters. All previously described and several novel cell classes were identified, with three previously-described classes unexpectedly found to be identical. A division into discrete classes however was not sufficient to describe the diversity of these cells, as continuous variation also occurred between and within classes. Latent factor analysis revealed that a single continuous variable could predict the expression levels of several genes, which correlated similarly with it across multiple cell types. Analysis of the genes correlating with this variable suggested it reflects a range from metabolically highly active faster-spiking cells that proximally target pyramidal cells, to slower-spiking cells targeting distal dendrites or interneurons. These results elucidate the complexity of inhibitory neurons in one of the simplest cortical structures, and show that characterizing these cells requires continuous modes of variation as well as discrete cell classes.

neuroscience↗