Expressional Profiling of Carpet Glia in the Developing Drosophila Eye Reveals Its Molecular Signature of Morphology Regulators

Abstract

Homeostasis in the nervous system requires intricate regulation and is largely accomplished by the blood–brain barrier (BBB). The major gate keeper of the vertebrate BBB is vascular endothelial cells, which form tight junctions (TJs). To gain insight into the development of the BBB, we studied the carpet glia, a subperineurial glial cell type with vertebrate TJ-equivalent septate junctions, in the developing Drosophila eye. The large and flat, sheet-like carpet glia, which extends along the developing eye following neuronal differentiation, serves as an easily accessible experimental system to understand the cell types that exhibit barrier function. We profiled transcribed genes in the carpet glia using targeted DNA adenine methyl-transferase identification, followed by next-generation sequencing (targeted DamID-seq) and found that the majority of genes expressed in the carpet glia function in cellular activities were related to its dynamic morphological changes in the developing eye. To unravel the morphology regulators, we silenced genes selected from the carpet glia transcriptome using RNA interference. The Rho1 gene encoding a GTPase was previously reported as a key regulator of the actin cytoskeleton. The expression of the pathetic ( path ) gene, encoding a solute carrier transporter in the developing eye, is specific to the carpet glia. The reduced expression of Rho1 severely disrupted the formation of intact carpet glia, and the silencing path impaired the connection between the two carpet glial cells, indicating the pan-cellular and local effects of Rho1 and Path on carpet glial cell morphology, respectively. Our study molecularly characterized a particular subperineurial cell type providing a resource for a further understanding of the cell types comprising the BBB.

Starvation-induced regulation of carbohydrate transport at the blood-brain barrier is TGF-β-signaling dependent

“…Fructose is also present albeit in low and highly fluctuating concentrations, making its nutritional role questionable (Blatt and Roces, 2001;Broughton et al, 2008;Lee and Park, 2004;Pasco and Léopold, 2012;Wyatt and Kalf, 1957). Transcriptome data of the BBB-forming glial cells suggests expression of several putative carbohydrate transporters (Desalvo et al, 2014;Ho et al, 2019). The closest homologues of mammalian GLUT1-4 are dmGlut1, dmSut1, dmSut2, dmSut3 and CG7882.…”

Early lineage segregation of the retinal basal glia in the Drosophila eye disc

“…The fly stocks used are UAS-H2B-RFP (Langevin et al, 2005), repo-RFP.nls 50 , UAS-Fucci 31 , C135-Gal4 15 , elav-Gal4 , C527-Gal4 , MZ97-Gal4 , UAS-ths , UAS-λ-htl , and UAS-GFP.nls were from Bloomington Drosophila Stock Center. Twin-spot MARCM tool was a gift from Dr. Hung-Hsiang Yu.…”

“…They have giant polyploid nucleus and broad membrane extension that each cover half of eye disc. The CGs are defined by their expression of moody-GAL4 14 , C135-GAL4 15 , 15IIa-GAL4 16 , the zinc-finger transcription factor Hunchback (Hb), two hb-GAL4 s (VT038544 and VT038545) and the NCAM Fasciclin 2 (Fas2) 17 . The membrane of the two CGs forms septate junction at the dorsoventral midline (equator) 14 .…”

“…Bnl is expressed in a subset of R8 PR neurons in the eye disc 26 and acts on Btl in SGs to prevent the precocious or overshot migration of SGs 27 . Pyr expressed in CG 15 is important to promote SG proliferation and motility 28 . SG proliferation and migration also requires the POU domain transcription factor Pdm3 23 and the N-terminal asparagine amidohydrolase homolog Öbek 22 .…”

Starvation-induced regulation of carbohydrate transport at the blood–brain barrier is TGF-β-signaling dependent

“…Fructose is also present, albeit in low and highly fluctuating concentrations, making its nutritional role questionable ( Blatt and Roces, 2001 ; Broughton et al, 2008 ; Lee and Park, 2004 ; Pasco and Léopold, 2012 ; Wyatt and Kalf, 1957 ). Transcriptome data of the BBB-forming glial cells suggests expression of several putative carbohydrate transporters ( DeSalvo et al, 2014 ; Ho et al, 2019 ). The closest homologs of mammalian GLUT1–4 are dmGlut1, dmSut1, dmSut2, dmSut3, and CG7882.…”