title: Orthodenticle and Kruppel homolog 1 regulate Drosophila photoreceptor maturation.
abstract: Neurons present a wide variety of morphologies that are associated with their specialized functions. However, to date very few pathways and factors regulating neuronal maturation, including morphogenesis, have been identified. To address this issue we make use here of the genetically amenable developing fly photoreceptor (PR). Whereas this sensory neuron is specified early during retinal development, its maturation spans several days. During this time, this neuron acquires specialized membrane domains while undergoing extensive polarity remodeling. In this study, we identify a pathway in which the conserved homeobox protein Orthodenticle (Otd) acts together with the ecdysone receptor (EcR) to directly repress the expression of the transcription factor (TF) Kruppel homolog 1 (Kr-h1). We demonstrate that this pathway is not required to promote neuronal specification but is crucial to regulate PR maturation. PR maturation includes the remodeling of the cell's epithelial features and associated apical membrane morphogenesis. Furthermore, we show that hormonal control coordinates PR differentiation and morphogenesis with overall development. This study demonstrates that during PR differentiation, transient repression of Kr-h1 represents a key step regulating neuronal maturation. Down-regulation of Kr-h1 expression has been previously associated with instances of neuronal remodeling in the fly brain. We therefore conclude that repression of this transcription factor represents a key step, enabling remodeling and maturation in a wide variety of neurons.
authors.affiliation: Medical Research Council Laboratory for Molecular Cell Biology and Cell Biology Unit, and Department of Cell and Developmental Biology,  University College London, London WC1E 6BT,  United Kingdom.
authors.forename: Pierre
authors.initials: P
authors.lastname: Fichelson
authors.forename: Amira
authors.initials: A
authors.lastname: Brigui
authors.forename: Franck
authors.initials: F
authors.lastname: Pichaud
mesh_terms: D000818:Animals; D047369:Chromatin Immunoprecipitation; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D004330:Drosophila / Q000254:growth & development*; D029721:Drosophila Proteins / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D018398:Homeodomain Proteins / Q000378:metabolism*; D007150:Immunohistochemistry; D051741:Kruppel-Like Transcription Factors / Q000378:metabolism*; D007814:Larva / Q000254:growth & development / Q000378:metabolism; D046228:Microarray Analysis; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D017956:Photoreceptor Cells, Invertebrate / Q000502:physiology*; D011987:Receptors, Steroid / Q000378:metabolism; D012160:Retina / Q000648:ultrastructure*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; C497242:Kr-h1 protein, Drosophila; D051741:Kruppel-Like Transcription Factors; D011987:Receptors, Steroid; C055469:ecdysone receptor; C093053:oc protein, Drosophila