CNS angiogenesis and barriergenesis occur simultaneously

Abstract

The blood-brain barrier (BBB) plays a vital role in the central nervous system (CNS). A comprehensive understanding of BBB development has been hampered by difficulties in observing the differentiation of brain endothelial cells (BECs) in real-time. Here, we generated two transgenic zebrafish line, Tg(glut1b:mCherry) and Tg(plvap:EGFP), to serve as in vivo reporters of BBB development. We showed that barriergenesis (i.e. the induction of BEC differentiation) occurs immediately as endothelial tips cells migrate into the brain parenchyma. Using the Tg(glut1b:mCherry) transgenic line, we performed a genetic screen and identified a zebrafish mutant with a nonsense mutation in gpr124, a gene known to play a role in CNS angiogenesis and BBB development. We also showed that our transgenic plvap:EGFP line, a reporter of immature brain endothelium, is initially expressed in newly formed brain endothelial cells, but subsides during BBB maturation. Our results demonstrate the ability to visualize the in vivo differentiation of brain endothelial cells into the BBB phenotype and establish that CNS angiogenesis and barriergenesis occur simultaneously.

3D brain angiogenesis model to reconstitute functional human blood–brain barrier in vitro

“…The transport of small hydrophilic molecules or potentially harmful materials is tightly regulated by specific transport systems on luminal and abluminal membranes of the brain endothelium in an ATP‐mediated manner (Abbott, Ronnback, & Hansson, ). Importantly, these unique BBB functionalities are acquired via complex cellular interactions during developmental angiogenesis of the CNS (Engelhardt, ; Umans et al, ; Vallon, Chang, Zhang, & Kuo, ). Although some molecular mechanisms involved in BBB phenotypes have been discovered, the complex interplay between BBB cell types has yet to be fully elucidated.…”

“…Moreover, CNS angiogenesisspecific molecular systems, such as Glut-1, are regulated by Wnt-βcatenin signaling, which is related to barrier-specific properties (Daneman et al, 2009;Obermeier et al, 2013). Umans et al (2017) also reported that barrier genesis of BBB occurs simultaneously with CNS angiogenesis in vivo using the zebrafish mutant model. These examples clearly show the strong interconnection between the maturation of BBB functionality and CNS angiogenesis ( Figure 1b).…”

“…interactions during developmental angiogenesis of the CNS (Engelhardt, 2003;Umans et al, 2017;Vallon, Chang, Zhang, & Kuo, 2014). Although some molecular mechanisms involved in BBB phenotypes have been discovered, the complex interplay between BBB cell types has yet to be fully elucidated.…”

Suppression of transcytosis regulates zebrafish blood-brain barrier development

“…This specialized endothelial layer forms the blood-brain barrier (BBB) and restricts the passage of substances between the blood and the brain parenchyma via two primary mechanisms: 1) specialized tight junction complexes between apposed endothelial cells to prevent intercellular transit (Reese and Karnovsky, 1967; Brightman and Reese, 1969) and 2) suppressing vesicular trafficking or transcytosis to prevent transcellular transit (Ben-Zvi et al, 2014; Andreone et al, 2015; Andreone et al, 2017). BBB selectivity is further refined with expression of substrate-specific transporters that dynamically regulate the influx of necessary nutrients and efflux of metabolic waste products (Sanchez-Covarrubias et al, 2014; Umans et al, 2017). While the BBB is comprised of endothelial cells, the surrounding perivascular cells including pericytes and astroglial cells, play a critical role in forming and maintaining barrier properties (Janzer and Raff, 1987; Armulik et al, 2010; Bell et al, 2010; Daneman et al, 2010; Wang et al, 2014).…”

“…As the simplest genetic model organism with an endothelial BBB (Jeong et al, 2008), zebrafish offer a powerful tool to study the cellular and molecular properties of the vertebrate BBB (Xie et al, 2010; Vanhollebeke et al, 2015; Umans et al, 2017; O’Brown et al, 2018; Quiñonez-Silvero et al, 2019). Zebrafish have served as a great model system to study vascular biology due to their large clutch size, rapid and external development, and transparency for in vivo whole organism live-imaging (Lawson and Weinstein, 2002; Jin et al, 2005; Santoro et al, 2007; Armer et al, 2009; Herbert et al, 2009; Phng et al, 2009; Geudens et al, 2010; Herbert et al, 2012; Wilkinson and van Eeden, 2014; Franco et al, 2015; Vanhollebeke et al, 2015; Matsuoka et al, 2016; Ulrich et al, 2016; Galanternik et al, 2017; Stratman et al, 2017; Geudens et al, 2018).…”