The Drosophila surface glia transcriptome: evolutionary conserved blood-brain barrier processes

Abstract

Central nervous system (CNS) function is dependent on the stringent regulation of metabolites, drugs, cells, and pathogens exposed to the CNS space. Cellular blood-brain barrier (BBB) structures are highly specific checkpoints governing entry and exit of all small molecules to and from the brain interstitial space, but the precise mechanisms that regulate the BBB are not well understood. In addition, the BBB has long been a challenging obstacle to the pharmacologic treatment of CNS diseases; thus model systems that can parse the functions of the BBB are highly desirable. In this study, we sought to define the transcriptome of the adult Drosophila melanogaster BBB by isolating the BBB surface glia with fluorescence activated cell sorting (FACS) and profiling their gene expression with microarrays. By comparing the transcriptome of these surface glia to that of all brain glia, brain neurons, and whole brains, we present a catalog of transcripts that are selectively enriched at the Drosophila BBB. We found that the fly surface glia show high expression of many ATP-binding cassette (ABC) and solute carrier (SLC) transporters, cell adhesion molecules, metabolic enzymes, signaling molecules, and components of xenobiotic metabolism pathways. Using gene sequence-based alignments, we compare the Drosophila and Murine BBB transcriptomes and discover many shared chemoprotective and small molecule control pathways, thus affirming the relevance of invertebrate models for studying evolutionary conserved BBB properties. The Drosophila BBB transcriptome is valuable to vertebrate and insect biologists alike as a resource for studying proteins underlying diffusion barrier development and maintenance, glial biology, and regulation of drug transport at tissue barriers.

TRAP-seq Profiling and RNAi-Based Genetic Screens Identify Conserved Glial Genes Required for Adult Drosophila Behavior

“…A recent study derived the transcriptome of Drosophila surface glia (DeSalvo et al, 2014), an important glial cell class that forms the fly blood-brain barrier. Unlike our studies, that analysis employed fluorescence activated cell sorting (FACS) procedures and gene microarrays as a readout; it identified 2733 genes that showed ≥1.5-fold enriched expression in surface glia (SGCs) relative to brain total RNA.…”

Multidrug transporters and organic anion transporting polypeptides protect insects against the toxic effects of cardenolides

“…Mdr65 is mainly expressed in the BBB, Mdr50 in the midgut, and Mdr49 in the Malpighian tubules. Mdr49 is also expressed at appreciable levels in the reproductive system, the BBB and the midgut (Supplemental Figure 1; Brown et al, 2014; DeSalvo et al, 2014; Graveley et al, 2011; Mayer et al, 2009). …”

“…And although redundancy between the midgut-expressed Mdr49 and -50 is possible, the PMdr49 mutant was more sensitive to biologically relevant levels of digitoxin (Figure 4B). Mdr49 is also highly and moderately expressed in the tubules and BBB, respectively (Supplemental Figure 2; DeSalvo et al, 2014). Of the Oatps, Oatp30B appeared to be the most important transporter in resistance to biologically relevant levels of ouabain, and this transporter is moderately expressed in all tissues including the BBB, midgut and tubules (Supplemental Figure 4).…”

Comparison between thaw-mounting and use of conductive tape for sample preparation in ToF-SIMS imaging of lipids in Drosophila microRNA-14 model

“…3(j) and 3(k) show a clear and significant spatial pattern that manifests as sharply denoted regions of cortex and glia surrounding the outer brain surface. [43][44][45] In the thaw-mounted sample, however, two ion signals in Figs. 3(i) and 3(l) came not only from the fat body of the head, but also from the stainless steel plates.…”