ABSTRACT
The midline glial cells are required for correct formation of the axonal pattern in the embryonic ventral nerve cord of Drosophila. Initially, six midline cells form an equivalence group with the capacity to develop as glial cells. By the end of embryonic development three to four cells are singled out as midline glial cells. Midline glia development occurs in two steps, both of which depend on the activation of the Drosophila EGF-receptor homolog and subsequent ras1/raf-mediated signal transduction. Nuclear targets of this signalling cascade are the ETS domain transcription factors pointedP2 and yan. In the midline glia pointedP2 in turn activates the transcription of argos, which encodes a diffusible negative regulator of EGF-receptor signalling.
Subject(s)
Central Nervous System/cytology , Central Nervous System/embryology , Drosophila Proteins , Drosophila/embryology , Neuroglia/cytology , Protein Kinases , Repressor Proteins , Saccharomyces cerevisiae Proteins , Animals , Central Nervous System/metabolism , DNA-Binding Proteins/metabolism , Drosophila/genetics , Drosophila/metabolism , ErbB Receptors/metabolism , Eye Proteins/metabolism , Gene Expression Regulation, Developmental , In Situ Hybridization , Mutation , Nerve Tissue Proteins , Neuroglia/metabolism , Phosphorylation , Proto-Oncogene Proteins/genetics , Proto-Oncogene Proteins/metabolism , Proto-Oncogene Proteins c-jun/metabolism , Receptors, Invertebrate Peptide/metabolism , Signal Transduction , Transcription Factors/genetics , ras Proteins/metabolismABSTRACT
The midline glial cells are required for correct formation of the axonal pattern in the embryonic ventral nerve cord of Drosophila. Initially, six midline cells form an equivalence group with the capacity to develop as glial cells. By the end of embryonic development three to four cells are singled out as midline glial cells. Midline glia development occurs in two steps, both of which depend on the activation of the Drosophila EGF-receptor homolog and subsequent ras1/raf-mediated signal transduction. Nuclear targets of this signalling cascade are the ETS domain transcription factors pointedP2 and yan. In the midline glia pointedP2 in turn activates the transcription of argos, which encodes a diffusible negative regulator of EGF-receptor signalling.
Subject(s)
Central Nervous System/embryology , Drosophila/embryology , Neuroglia/cytology , Animals , Central Nervous System/metabolism , DNA-Binding Proteins , Drosophila/genetics , Drosophila Proteins , ErbB Receptors/metabolism , Gene Expression Regulation, Developmental , Nerve Tissue Proteins , Neuroglia/metabolism , Phosphorylation , Proto-Oncogene Proteins/genetics , Signal Transduction , Transcription Factors , ras Proteins/metabolismABSTRACT
Each abdominal neuromere of a Drosophila embryo contains about 60 glial cells [Klämbt C, Goodman CS (1991): Glia 4:205-213; Ito et al. (1995): Roux's Arch Dev Biol, 204:284-307]. Among these, the midline and longitudinal glia are described to some detail. The midline glia are located dorsally in the nerve cord ensheathing the two segmental commissures. They are required for the proper establishment of commissures. The longitudinal glia, the A and B glia, and the segment boundary cells (SBC) are covering the longitudinal connectives. The longitudinal glia prefigure longitudinal axon paths and appear capable of regulating the expression of neuronal antigens. In the following we summarize the knowledge on the function of these glial cells.
