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March 11, 2025
Dylan Sebo, Pharmaceutical Sciences graduate student (Taylor Research Group), will be defending his PhD research thesis:
Intercellular Signaling Regulates Blood-brain Barrier Development and Influences Early Neuroinflammation in Zebrafish
Tuesday, March 11th, 2025, 10:00am
Room 2336, Rennebohm Hall
Abstract:
The blood-brain barrier (BBB) plays a critical role in the function of the central nervous system (CNS) by controlling the entry of both essential and harmful substances into the brain. During neurovascular development, brain endothelial cells (BECs) respond to signals secreted from cells in their microenvironment that induce angiogenesis, the growth of new blood vessels, and barriergenesis, the acquisition of barrier properties. Differentiated BECs and the cells of the neurovascular unit (NVU) that surround and support them create a selectively permeable barrier that maintains CNS homeostasis allowing for proper CNS function. Conversely, dysfunction of the BBB creates a deleterious environment which contributes to the pathologies of many CNS disease states. Furthermore, neuroinflammation that often accompanies BBB dysfunction exacerbates clinical symptoms and can lead to secondary presentations. In this thesis, zebrafish (Danio rerio) are used to investigate mechanisms of NVU interactions that mediate BBB development and mechanisms of inflammatory signaling that mediate neuroinflammation. Specifically, BBB development depends on Wnt ligand release from NVU cells to activate Wnt/β-catenin signaling in BECs. However, NVU cells also require Wnt/β-catenin signaling to guide CNS development. While necessary for both, the critical need for regulation of Wnt/β-catenin signaling in each cell type to prevent interplay between these processes has not been investigated. Here, we describe a novel inverse correlation between Wnt/β-catenin signaling activation in BECs versus NVU cells in their microenvironment suggesting that Wnt/β-catenin signaling in the NVU regulates Wnt/β-catenin signaling in nearby BECs. We then created a model of activated Wnt/β-catenin signaling throughout the CNS to investigate and detail the effects of aberrant Wnt/β-catenin signaling in the NVU on neurovascular development and neuroinflammation. Additionally, we sought to better understand the mechanisms that regulate such neuroinflammation. Il-1β is known to be a master regulator of inflammation and is often used to model and study inflammation in zebrafish. Despite this, zebrafish lack genome annotation and ortholog identification of the primary receptor of Il-1β, Il-1r1, limiting investigation of the mechanisms regulating inflammation. Here, we used a combination of in silico analysis and functional assays in a zebrafish model of Il-1β-induced inflammation to identify the zebrafish ortholog of Il-1r1. This significantly increases the understanding of inflammation in zebrafish and furthers its utility as a model organism to study inflammation. Overall, the work presented in this thesis increases understanding of the mechanisms involved in both BBB development and the inflammation that accompanies BBB dysfunction. Finally, this thesis provides important implications of these results and presents further questions to be investigated with the goal of increasing our ability to understand and treat CNS pathologies.
