Biology subjects

Murdock, M. H.

Publications and source records attributed to Murdock, M. H..

3 recordsLinked to original sources

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↗

bioRxiv2022

Single-cell multi-region dissection of brain vasculature in Alzheimer's Disease

Cerebrovascular breakdown occurs early in Alzheimers Disease (AD), but its cell-type-specific molecular basis remains uncharacterized. Here, we characterize single-cell transcriptomic differences in human cerebrovasculature across 220 AD and 208 control individuals and across 6 brain regions. We annotate 22,514 cerebrovascular cells in 11 subtypes of endothelial, pericyte, smooth muscle, perivascular fibroblast, and ependymal cells, and how they differ in abundance and gene expression between brain regions. We identify 2,676 AD-differential genes, including lower expression of PDGFRB in pericytes, and ABCB1 and ATP10A in endothelial cells. These AD-differential genes reveal common upstream regulators, including MECOM, EP300, and KLF4, whose targeting may help restore vasculature function. We find coordinated vasculature-glial-neuronal co-expressed gene modules supported by ligand-receptor pairs, involved in axon growth/degeneration and neurogenesis, suggesting mechanistic mediators of neurovascular unit dysregulation in AD. Integration with AD genetics reveals 125 AD-differential genes directly linked to AD-associated genetic variants (through vasculature-specific eQTLs, Hi-C, and correlation-based evidence), 559 targeted by AD-associated regulators, and 661 targeted by AD-associated ligand-receptor signaling. Lastly, we show that APOE4-genotype associated differences are significantly enriched among AD-associated genes in capillary and venule endothelial cells, and subsets of pericytes and fibroblasts, which underlie the vascular dysregulation in APOE4-associated cognitive decline. Overall, our multi-region molecular atlas of differential human cerebrovasculature genes and pathways in AD can help guide early-stage AD therapeutics.

neuroscience↗

bioRxiv2020

Improved genetically encoded near-infrared fluorescent calcium ion indicators for in vivo imaging

Near-infrared (NIR) genetically-encoded calcium ion (Ca2+) indicators (GECIs) can provide advantages over visible wavelength fluorescent GECIs in terms of reduced phototoxicity, minimal spectral cross-talk with visible-light excitable optogenetic tools and fluorescent probes, and decreased scattering and absorption in mammalian tissues. Our previously reported NIR GECI, NIR-GECO1, has these advantages but also has several disadvantages including lower brightness and limited fluorescence response compared to state-of-the-art visible wavelength GECIs, when used for imaging of neuronal activity. Here, we report two improved NIR GECI variants, designated NIR-GECO2 and NIR-GECO2G, derived from NIR-GECO1. We characterized the performance of the new NIR GECIs in cultured cells, acute mouse brain slices, and C. elegans and Xenopus laevis in vivo. Our results demonstrate that NIR-GECO2 and NIR-GECO2G provide substantial improvements over NIR-GECO1 for imaging of neuronal Ca2+ dynamics.

molecular biology↗