Expression of a set of glial cell-specific markers in the Drosophila embryonic central nervous system

Abstract

The types of glia in the central nervous system (CNS) of the Drosophila embryo include longitudinal glia (LG), cell body glia (CBG), and peripheral glia (PG). Transcription factors, such as glial cell missing and reverse polarity, are well-established general glial cell markers. Only a few glial cell-specific markers have been identified in the Drosophila embryonic CNS, thus far. In the present study, we employed the glial cell-specific markers for LG (vir-1/CG5453 and CG31235), CBG (fabp/CG6783 and CG11902), and PG (CG2310 and moody/CG4322), and comprehensively analyzed their expression patterns, during the embryonic CNS development. Our study validated the specificity of a set of glial markers, and further revealed their spatio-temporal expression patterns, which will aid in the understanding of the developmental lineage, and investigating their role in the development and homeostasis of the Drosophila CNS in vivo.

Fig. 1.. The expression of the LG-specific markers, vir-1/CG5453 and CG31235. (A-D) vir-1/CG5453 expression is detected in the midline cells and the tracheal precursor cells, at stage 11. (E-H) Its expression in the trachea and 3-4 midline cells (arrow) becomes prominent in a segmentally repetitive fashion, at stage 12. (I-P) At stages 13 and 14, it is expressed in approximately 4-5 LG (arrowhead) of each segment, in addition to tracheal cells (arrow) and midline cells. (Q-T) Its expression becomes stronger in the LG and midline cells, at stage 15. (U-X) vir-1/CG5453 expression reaches the maximum level at stage 16, and the first vir-1/CG5453-positive oenocytes (arrow) are detected. (A'-C') It first appears in the LG (arrowheads) at stage 11. (D'-F') Its expression is repeated in every 2-3 LG (arrowhead) per hemisegment, and becomes detectable shortly thereafter, in the brain at stage 12. (G'-I') The CG31235-expressing LG are connected along the longitudinal tracts, at stage 13. (J'-O') The number of CG31235-positive LG increases to approximately 4-5, at stages 14 and 15. (P'-R') The number of CG31235-positive LG increases to 5-6 cells per segment, at stages 16. (S'-U') Its expression is observed in a few commissural glia, in addition to LG, at stage 17. In all panels, anterior is to the left. In panels A, C, E, G, I, K, M, O, Q, S, U and W, side views are shown. In panels A', D', G', J', M', P' and S', side views are shown. In all the remaining panels, ventral views are shown.

Fig. 2.. The expression of the CBG-specific markers, fabp/CG6783 and CG11902. (A-C) It is initially detected in the SG (arrowhead) in each segment, at stages 12. (D-F) At stage 13, its expression becomes prominent in MM-CBGs (arrow), intermediate and lateral glia. (G-O) Its expression becomes stronger in many MM-CBG and SG, and is detected in the brain at stages 14, 15 and 16. (P-R) It reaches the maximum level of expression in the brain and ventral nerve cord at stage 17. (A'-C') CG11902 expression appears in a pair of SG (arrowhead) in each segment, at stage 10. (D'-F') At stage 11, it is expressed in the medial CBG (arrow), which are located adjacent to the anterior SG in each segment. (G'-I') At stage 12, it is detected in the intermediate glia (arrowhead) that had resulted from the division of SG (white arrow) in each segment, and medial CBGs (arrow) are divided into two medial CBG in the thoracic segments. (J'-L') Its expression becomes weaker at stage 13. (M'-O') Its expression becomes significantly reduced by stage 14. (P'-R') Its expression remains in the medial CBG, intermediate and lateral glia of each segment at stage 15. In all panels, anterior is to the left, and each segment is marked by staining with anti-En antibody (brown). In panels A, A', D, D', G, G', J, J', M, M', P and P', side views are shown. In all the remaining panels, ventral views are shown.

Fig. 3.. The expression of the PG marker, CG2310. (A-H) CG2310 expression is observed in the lateral neuroectoderm (arrowheads) of each segment, at stages 11 and 12. (I-L) It is expressed only in the PG that are located at the boundary between the ventral nerve cord and the lateral epidermis (arrowhead), at stage 13. (M-T) CG2310-expressing PG (arrows) begin to migrate towards the lateral side at stage 14, and continue to migrate further away along the sensory axonal tracts, at stage 15. (U-X) It is expressed in 3-4 PG (arrows) along the sensory axonal tracts, at stage 16. In all panels, anterior is to the left. In panels C, D, G, H, K, L, O, P, S, T, W and X, side views are shown. In all the remaining panels, ventral views are shown. In panels Q-X, sensory axonal tracts are stained with 22C10 antibody (brown).

Fig. 4.. The expression of the PG marker, moody/CG4322. (A-F) It is initially detected in the head mesoderm (arrowhead) and the anterior midgut (white arrowhead), at stages 9 and 10. (G-I) It is expressed in a pair of LG (arrowhead) in each segment, at stage 11. (J-O) At stages 12 and 13, it is also expressed in PG (arrowhead), in addition to LG. (P-R) moody/CG4322-expressing PG migrate along the sensory axonal tracts in each segment, at stage 14. (S-X) moody/CG4322-positive 3-4 PG are observed in each sensory axonal tract, at stages 15 and 16. In all panels, anterior is to the left. In panels A, B, D, E, G, H, J, M, P, S, U, V and X, side views are shown. In all the remaining panels, ventral views are shown.