title: The Black cells phenotype is caused by a point mutation in the Drosophila pro-phenoloxidase 1 gene that triggers melanization and hematopoietic defects.
abstract: Melanization contributes to arthropod-specific innate immunity through deposition of melanin at wound sites or around parasites, with concomitant release of microbicidal reactive oxygen species. Melanization requires sequential activation of proteolytic enzymes in the hemolymph, including the final enzyme pro-phenoloxidase. Black cells (Bc) is a mutation causing spontaneous melanization of Drosophila crystal cells, a hemocyte cell type producing phenoloxidases. Bc individuals exhibit circulating black spots but fail to melanize upon injury. Although Bc is widely used as a loss-of-function mutant of phenoloxidases, the mutation causing Bc remained unknown. Here, we identified a single point mutation in the pro-phenoloxidase 1 (PPO1) gene of Bc flies causing an Alanine to Valine change in the C-terminal domain of PPO1, predicted to affect the conformation of the N-terminal pro-domain cleavage site at a distance and causing uncontrolled catalytic activity. Genomic insertion of a PPO1(A480V) transgene phenocopies Black cells, proving that A480V is indeed the causal mutation of the historical Bc phenotype.
authors.affiliation: Global Health Institute, Swiss Federal Institute of Technology, Station 19, CH-1015 Lausanne, Switzerland. Electronic address: claudine.neyen@epfl.ch.
authors.forename: Claudine
authors.initials: C
authors.lastname: Neyen
authors.affiliation: Global Health Institute, Swiss Federal Institute of Technology, Station 19, CH-1015 Lausanne, Switzerland.
authors.forename: Olivier
authors.initials: O
authors.lastname: Binggeli
authors.affiliation: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
authors.forename: Pietro
authors.initials: P
authors.lastname: Roversi
authors.affiliation: Global Health Institute, Swiss Federal Institute of Technology, Station 19, CH-1015 Lausanne, Switzerland.
authors.forename: Lise
authors.initials: L
authors.lastname: Bertin
authors.affiliation: Global Health Institute, Swiss Federal Institute of Technology, Station 19, CH-1015 Lausanne, Switzerland.
authors.forename: Maroun Bou
authors.initials: MB
authors.lastname: Sleiman
authors.affiliation: Global Health Institute, Swiss Federal Institute of Technology, Station 19, CH-1015 Lausanne, Switzerland. Electronic address: bruno.lemaitre@epfl.ch.
authors.forename: Bruno
authors.initials: B
authors.lastname: Lemaitre
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D004156:Catechol Oxidase / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics* / Q000276:immunology; D004331:Drosophila melanogaster; D004792:Enzyme Precursors / Q000235:genetics*; D006434:Hemocytes / Q000276:immunology; D006458:Hemolymph / Q000201:enzymology / Q000276:immunology; D007113:Immunity, Innate / Q000235:genetics* / Q000276:immunology; D008543:Melanins / Q000378:metabolism*; D010641:Phenotype; D017354:Point Mutation / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D017422:Sequence Analysis, DNA
chemical_list: D029721:Drosophila Proteins; D004792:Enzyme Precursors; D008543:Melanins; D017382:Reactive Oxygen Species; C038451:pro-phenoloxidase; D004156:Catechol Oxidase
keywords: Crystal cell; Drosophila; Hematopoiesis; Melanization; Phenoloxidase