RESUMO
Environmental factors such as the availability of oxygen are instructive cues that regulate stem cell maintenance and differentiation. We used a genetically encoded biosensor to monitor the hypoxic state of neural cells in the larval brain of Drosophila The biosensor reveals brain compartment and cell-type specific levels of hypoxia. The values correlate with differential tracheolation that is observed throughout development between the central brain and the optic lobe. Neural stem cells in both compartments show the strongest hypoxia response while intermediate progenitors, neurons and glial cells reveal weaker responses. We demonstrate that the distance between a cell and the next closest tracheole is a good predictor of the hypoxic state of that cell. Our study indicates that oxygen availability appears to be the major factor controlling the hypoxia response in the developing Drosophila brain and that cell intrinsic and cell-type specific factors contribute to modulate the response in an unexpected manner.This article has an associated First Person interview with the first author of the paper.
Assuntos
Encéfalo/crescimento & desenvolvimento , Encéfalo/patologia , Compartimento Celular , Drosophila melanogaster/citologia , Drosophila melanogaster/crescimento & desenvolvimento , Hipóxia/patologia , Animais , Técnicas Biossensoriais , Diferenciação Celular , Hipóxia Celular/efeitos dos fármacos , Regulação da Expressão Gênica/efeitos dos fármacos , Glicólise/efeitos dos fármacos , Glicólise/genética , Proteínas de Fluorescência Verde/metabolismo , Hipóxia/genética , Larva/efeitos dos fármacos , Células Neuroepiteliais/efeitos dos fármacos , Células Neuroepiteliais/metabolismo , Lobo Óptico de Animais não Mamíferos/patologia , Oxigênio/farmacologiaRESUMO
In a previous study, we analyzed and described the features of the degeneration of the protocerebral tract (PCT) of the crustacean Ucides cordatus, after the extirpation of the eyestalk. In that study, among axons with axoplasmic degeneration, cells with granules resembling blood cells (hemocytes) were seen. Therefore, in the present study, we characterized the circulating hemocytes and compared them with the cells recruited to a lesion, which was produced as in the former study. Using histochemistry, immunohistochemistry, and electron microscopy (transmission and scanning), we confirmed that circulating and recruited cells display a similar morphology. Therefore, in the crab, hemocytes were attracted to the lesion site in the acute stage of degeneration, appearing near local glial cells that showed signs of being responsive. Some of the attracted hemocytes displayed a morphology that was considered to be possibly activated blood cells. Also, the cells that migrated to the injured PCT displayed features, such as the presence of hydrolytic enzymes and an ability to phagocytize neural debris, similar to those of vertebrates. In summary, our results indicate that hemocytes were not only phagocytizing neural debris together with glial cells but also that they may be concerned with creating a favorable environment for regenerating events.