Neurotrophic and Gliatrophic Contexts in <i>Drosophila</i>

Abstract

Trophic interactions in the vertebrate nervous system enable the adjustment of cell number and axon guidance, targeting and connectivity. Computational analysis of the sequenced Drosophila genome failed to identify some of the main trophic factors, the neuregulins and neurotrophins, as well as many other genes. This provoked speculations that the Drosophila nervous system might not require such regulative interactions. Here we review abundant cellular, genetic and functional data that demonstrate the existence of both neurotrophic and gliatrophic interactions in the Drosophila nervous system. Glial survival is maintained by the epidermal growth factor receptor (EGFR) signaling pathway in response to the ligands Spitz, a transforming growth factor-α (TGF-α) signaling molecule, and Vein, a neuregulin homologue. Cellular and genetic evidence predicts the existence of neuronal trophic factors operating at least in the Drosophila embryo during axon guidance and, in the visual system, during the targeting of retinal axons in the brain.

DrosophilaActivin-β and the Activin-like product Dawdle function redundantly to regulate proliferation in the larval brain

“…As glial cells provide both guidance cues and trophic factors for optic lobe development (Hidalgo et al, 2006), and because their numbers are reduced in babo mutants, we asked if selective expression of babo in glial cells was able to suppress any aspect of the babo mutant phenotype. As shown in Fig.…”

Identification of downstream targets of the Bone Morphogenetic Protein pathway in the Drosophila nervous system

“…Peptides of the Transforming Growth Factor-b (TGF-b) super family are pleiotropic intercellular signals involved in virtually every developmental process in metazoans, as reflected in the large number of diseases resulting from mutations in components of the pathway (Harradine and Akhurst, 2006). TGF-bs are required for ectodermal differentiation into epidermis and nervous system, dorsoventral patterning of the neural tube, neural crest induction, neuronal and glial differentiation, neuronal migration, axonal path-finding, and adult neurogenesis (De Robertis and Kuroda, 2004;Bovolenta, 2005;Cayuso and Marti, 2005;Salinas, 2005;Hidalgo et al, 2006;Takahashi and Liu, 2006;Levine and Brivanlou, 2007;Colak et al, 2008).…”

Further understanding of fat biology: Lessons from a fat fly

“…Examples of the DDC model are frequently observed in low organisms. For instance, the nervous systems of humans and flies display tremendous conservation in function and structure, but nevertheless two families of major trophic factors, neurotrophin and neuregulin, and their corresponding receptors are not identified in flies (Hidalgo et al, 2006). Instead, some epidermal growth factors (EGFs) and their receptors act as functional homologs of neuregulin in certain contexts (Hidalgo et al, 2006).…”

“…For instance, the nervous systems of humans and flies display tremendous conservation in function and structure, but nevertheless two families of major trophic factors, neurotrophin and neuregulin, and their corresponding receptors are not identified in flies (Hidalgo et al, 2006). Instead, some epidermal growth factors (EGFs) and their receptors act as functional homologs of neuregulin in certain contexts (Hidalgo et al, 2006). More recently, spätzle (spz) 2, also called Drosophila Neurotrophin 1 (DNT1), was identified as the first homolog of neurotrophin in flies (Zhu et al, 2008).…”