title: Ecdysone-dependent and ecdysone-independent programmed cell death in the developing optic lobe of Drosophila.
abstract: The adult optic lobe of Drosophila develops from the primordium during metamorphosis from mid-3rd larval stage to adult. Many cells die during development of the optic lobe with a peak of the number of dying cells at 24 h after puparium formation (h APF). Dying cells were observed in spatio-temporal specific clusters. Here, we analyzed the function of a component of the insect steroid hormone receptor, EcR, in this cell death. We examined expression patterns of two EcR isoforms, EcR-A and EcR-B1, in the optic lobe. Expression of each isoform altered during development in isoform-specific manner. EcR-B1 was not expressed in optic lobe neurons from 0 to 6h APF, but was expressed between 9 and 48 h APF and then disappeared by 60 h APF. In each cortex, its expression was stronger in older glia-ensheathed neurons than in younger ones. EcR-B1 was also expressed in some types of glia. EcR-A was expressed in optic lobe neurons and many types of glia from 0 to 60 h APF in a different pattern from EcR-B1. Then, we genetically analyzed EcR function in the optic lobe cell death. At 0 h APF, the optic lobe cell death was independent of any EcR isoforms. In contrast, EcR-B1 was required for most optic lobe cell death after 24 h APF. It was suggested that cell death cell-autonomously required EcR-B1 expressed after puparium formation. βFTZ-F1 was also involved in cell death in many dying-cell clusters, but not in some of them at 24 h APF. Altogether, the optic lobe cell death occurred in ecdysone-independent manner at prepupal stage and ecdysone-dependent manner after 24 h APF. The acquisition of ecdysone-dependence was not directly correlated with the initiation or increase of EcR-B1 expression.
authors.affiliation: Developmental Biology, Tokyo University of Agriculture and Technology, 3-5-8, Fuchu-shi, Tokyo 183-8509, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Hara
authors.forename: Keiichiro
authors.initials: K
authors.lastname: Hirai
authors.forename: Yu
authors.initials: Y
authors.lastname: Togane
authors.forename: Hiromi
authors.initials: H
authors.lastname: Akagawa
authors.forename: Kikuo
authors.initials: K
authors.lastname: Iwabuchi
authors.forename: Hidenobu
authors.initials: H
authors.lastname: Tsujimura
mesh_terms: D000818:Animals; D017209:Apoptosis; D003433:Crosses, Genetic; D004330:Drosophila / Q000196:embryology / Q000378:metabolism*; D004440:Ecdysone / Q000378:metabolism* / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D008675:Metamorphosis, Biological; D018613:Microscopy, Confocal / Q000379:methods; D008954:Models, Biological; D009154:Mutation; D009474:Neurons / Q000378:metabolism; D009899:Optic Lobe, Nonmammalian / Q000196:embryology*; D020033:Protein Isoforms; D012330:RNA, Double-Stranded / Q000378:metabolism; D013997:Time Factors
chemical_list: D020033:Protein Isoforms; D012330:RNA, Double-Stranded; D004440:Ecdysone