Biology subjects

Cerit, O.

Publications and source records attributed to Cerit, O..

3 recordsLinked to original sources

bioRxiv2023

Engineered 3D Immuno-Glial-Neurovascular Human Brain Model

Patient-specific, human-based cellular models integrating a biomimetic blood-brain barrier (BBB), immune, and myelinated neuron components are critically needed to enable accelerated, translationally relevant discovery of neurological disease mechanisms and interventions. By engineering a novel brain-mimicking 3D hydrogel and co-culturing all six major brain cell types derived from patient iPSCs, we have constructed, characterized, and utilized a multicellular integrated brain (miBrain) immuno-glial-neurovascular model with in vivo-like hallmarks inclusive of neuronal activity, functional connectivity, barrier function, myelin-producing oligodendrocyte engagement with neurons, multicellular interactions, and transcriptomic profiles. We implemented the model to study Alzheimers Disease pathologies associated with APOE4 genetic risk. APOE4 miBrains differentially exhibit amyloid aggregation, tau phosphorylation, and astrocytic GFAP. Unlike the co-emergent fate specification of glia and neurons in organoids, miBrains integrate independently differentiated cell types, a feature we harnessed to identify that APOE4 in astrocytes promotes neuronal tau pathogenesis and dysregulation through crosstalk with microglia.

neuroscience↗

bioRxiv2022

Distinct effects of disease-associated TREM2 R47H/+ and T66M mutations on iPSC-derived microglia.

Genetic findings have highlighted key roles for microglia in the pathology of neurodegenerative conditions such as Alzheimers disease (AD). Distinct mutations in the microglial protein TREM2 (triggering receptor expressed on myeloid cells 2) are associated with different forms of neurodegeneration in humans; R47H/+ mutations increase AD risk, while loss-of-function mutations such as TREM2 T66M result in more severe forms of neurodegeneration. We employed gene editing and stem cell models to gain insight into the effects of these mutations on human iPSC-derived microglia. We found divergent effects of TREM2 R47H/+ and T66M mutations on gene expression, with R47H/+ cells exhibiting a pro-inflammatory gene expression signature. Both the TREM2 R47H/+ and T66M mutations caused similar impairments in microglial movement and the uptake of multiple substrates, while R47H/+ microglia were hyper-responsive to inflammatory stimuli, consistent with their gene expression signature. We developed an in vitro laser-induced injury model in neuron-microglia co-cultures, finding an impaired injury response by TREM2 R47H/+ microglia. Furthermore, in xenotransplantation experiments, mouse brains transplanted with TREM2 R47H/+ microglia exhibited reduced synaptic density. Consistently, we observed upregulation of multiple complement cascade components in TREM2 R47H/+ microglia, suggesting that inappropriate synaptic pruning may underlie the effect. Thus, these findings identify shared and distinct effects of these two TREM2 mutations on microglial gene expression and function. While the TREM2 T66M mutation impairs microglial movement and uptake processes, the TREM2 R47H/+ mutation additionally confers multiple potentially detrimental effects on human microglia, likely to underlie its association with AD.

neuroscience↗

bioRxiv2022

Lipid Accumulation Induced by APOE4 Impairs Microglial Surveillance of Neuronal-Network Activity

Apolipoprotein E4 (APOE4) is the greatest known genetic risk factor for developing late- onset Alzheimers disease and its expression in microglia is associated with pro- inflammatory states. How the interaction of APOE4 microglia with neurons differs from microglia expressing the disease-neutral allele APOE3 is currently unknown. Here, we employ CRISPR-edited induced pluripotent stem cells (iPSCs) to dissect the impact of APOE4 in neuron-microglia communication. Our results reveal that APOE4 induces a distinct metabolic program in microglia that is marked by the accumulation of intracellular neutral lipid stores through impaired lipid catabolism. Importantly, this altered lipid-accumulated state shifts microglia away from homeostatic surveillance and renders APOE4 microglia weakly responsive to neuronal activity. By examining the transcriptional signatures of APOE3 versus APOE4 microglia before and after exposure to neuronal conditioned media, we further established that neuronal soluble cues differentially induce a lipogenic program in APOE4 microglia that exacerbates pro- inflammatory signals. Pharmacological blockade of lipogenesis in APOE4 microglia is sufficient to diminish intracellular lipid accumulation and restore microglial homeostasis. Remarkably, unlike APOE3 microglia that support neuronal network activity, co-culture of APOE4 microglia with neurons disrupts the coordinated activity of neuronal ensembles. We identified that through decreased uptake of extracellular fatty acids and lipoproteins, APOE4 microglia disrupts the net flux of lipids which results in decreased neuronal activity via the potentiation of the lipid-gated K+ channel, GIRK3. These findings suggest that neurological diseases that exhibit abnormal neuronal network-level disturbances may in part be triggered by impairment in lipid homeostasis in non-neuronal cells, underscoring a novel therapeutic route to restore circuit function in the diseased brain. O_FIG O_LINKSMALLFIG WIDTH=166 HEIGHT=200 SRC="FIGDIR/small/484146v1_ufig1.gif" ALT="Figure 1"> View larger version (60K): org.highwire.dtl.DTLVardef@4d4a9corg.highwire.dtl.DTLVardef@5d888corg.highwire.dtl.DTLVardef@afa191org.highwire.dtl.DTLVardef@984340_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗