Project description:The blood-brain barrier (BBB) is an evolutionary conserved tissue interface that possesses potent chemical protection properties functioning to strictly modulate the central nervous system (CNS) microenvironment. These same properties, including tight cellular junctions and efflux transporters, also limit access of CNS-active pharmaceuticals. For this reason, understanding the molecular mechanisms that regulate BBB chemical protection is of great biomedical interest. The BBB of Drosophila consists of two surface glia layers that completely surround the brain. This tissue interface contains both “tight” cellular junctions (termed septate junctions) and drug efflux transporters; thus, the Drosophila BBB can potentially serve as a model for understanding complex regulation of BBB physiology. In this study, we show reciprocal compensatory responses following disruption of critical BBB genes: deletion of the septate junction regulator Moody causes increased drug efflux and up-regulation of the P-glycoprotein ortholog Mdr65; conversely, disruption of Mdr65 expression causes increased septate junction tightness and up-regulation of Moody. We reveal these homeostatic interactions with physiologic observations, gene expression data, and anatomical images of the BBB surface. Whole brain microarray data point to responses that are consistent with our physiologic observations and these responses are likely localized to the BBB. To our knowledge, this is the first observation of a reciprocal compensatory interaction at a tissue barrier. Furthermore, this study paves the way for future studies elucidating the direct pathways that link GPCR signaling and drug transporter regulation at the BBB. The main comparisons are between WT_new, C17 (Moody null), and PMdr65 (Mdr65 null). Since WT_new were processed on a different day than C17 and PMdr65, we also included another WT sample (WT_old) to control for genes that change depending on batch effects. Since the mutants are also in a different genetic background than WT, we also included a control that is in a similar background (UAS_control).

Project description:The neurovascular unit (NVU) is a complex multicellular structure that helps maintain cerebral homeostasis and blood-brain barrier (BBB) integrity. While extensive evidence links NVU alterations to cerebrovascular diseases and neurodegeneration, the underlying molecular mechanisms remain unclear. Here, we use zebrafish embryos carrying a mutation in Scavenger Receptor B2, a highly conserved endolysosomal protein expressed predominantly in Radial Glia Cells (RGCs), to investigate the interplay among different NVU components. Through live imaging and genetic manipulations, we demonstrate that compromised acidification of the endolysosomal compartment in mutant RGCs leads to impaired Notch3 signaling, thereby inducing excessive neurogenesis and reduced glial differentiation. We further demonstrate that alterations to the neuron/glia balance result in impaired VEGF and Wnt signaling, leading to severe vascular defects, hemorrhages, and a leaky BBB. Altogether, our findings provide novel insights into NVU formation and function and offer new avenues for investigating diseases involving white matter defects and vascular abnormalities. The neurovascular unit (NVU) is a complex multicellular structure that helps maintain cerebral homeostasis and blood-brain barrier (BBB) integrity. While extensive evidence links NVU alterations to cerebrovascular diseases and neurodegeneration, the underlying molecular mechanisms remain unclear. Here, we use zebrafish embryos carrying a mutation in Scavenger Receptor B2, a highly conserved endolysosomal protein expressed predominantly in Radial Glia Cells (RGCs), to investigate the interplay among different NVU components. Through live imaging and genetic manipulations, we demonstrate that compromised acidification of the endolysosomal compartment in mutant RGCs leads to impaired Notch3 signaling, thereby inducing excessive neurogenesis and reduced glial differentiation. We further demonstrate that alterations to the neuron/glia balance result in impaired VEGF and Wnt signaling, leading to severe vascular defects, hemorrhages, and a leaky BBB. Altogether, our findings provide novel insights into NVU formation and function and offer new avenues for investigating diseases involving white matter defects and vascular abnormalities. The neurovascular unit (NVU) is a complex multicellular structure that helps maintain cerebral homeostasis and blood-brain barrier (BBB) integrity. While extensive evidence links NVU alterations to cerebrovascular diseases and neurodegeneration, the underlying molecular mechanisms remain unclear. Here, we use zebrafish embryos carrying a mutation in Scavenger Receptor B2, a highly conserved endolysosomal protein expressed predominantly in Radial Glia Cells (RGCs), to investigate the interplay among different NVU components. Through live imaging and genetic manipulations, we demonstrate that compromised acidification of the endolysosomal compartment in mutant RGCs leads to impaired Notch3 signaling, thereby inducing excessive neurogenesis and reduced glial differentiation. We further demonstrate that alterations to the neuron/glia balance result in impaired VEGF and Wnt signaling, leading to severe vascular defects, hemorrhages, and a leaky BBB. Altogether, our findings provide novel insights into NVU formation and function and offer new avenues for investigating diseases involving white matter defects and vascular abnormalities.

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Drosophila melanogaster

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