RESUMO
Fibrillarin (Fbl) is a highly conserved protein that plays an essential role in ribosome biogenesis and more particularly in the methylation of ribosomal RNAs and rDNA histones. In cellular models, FBL was shown to play an important role in tumorigenesis and stem cell differentiation. We used the zebrafish as an in vivo model to study Fbl function during embryonic development. We show here that the optic tectum and the eye are severely affected by Fbl depletion whereas ventral regions of the brain are less impacted. The morphogenesis defects are associated with impaired neural differentiation and massive apoptosis. Polysome gradient experiments show that fbl mutant larvae display defects in ribosome biogenesis and activity. Strikingly, flow cytometry analyses revealed different S-phase profiles between wild-type and mutant cells, suggesting a defect in S-phase progression.
Assuntos
Diferenciação Celular/genética , Proteínas Cromossômicas não Histona/metabolismo , Mesencéfalo/embriologia , Retina/embriologia , Fase S/genética , Animais , Apoptose , Larva/metabolismo , Mesencéfalo/metabolismo , Morfogênese/genética , Neurogênese/genética , RNA Ribossômico/metabolismo , Retina/metabolismo , Peixe-Zebra/embriologiaRESUMO
In mammals, neuroepithelial cells play an essential role in embryonic neurogenesis, whereas glial stem cells are the principal source of neurons at postembryonic stages. By contrast, neuroepithelial-like stem/progenitor (NE) cells have been shown to be present throughout life in teleosts. We used three-dimensional (3D) reconstructions of cleared transgenic wdr12:GFP medaka brains to demonstrate that this cell type is widespread in juvenile and to identify new regions containing NE cells. We established the gene expression profile of optic tectum (OT) NE cells by cell sorting followed by RNA-seq. Our results demonstrate that most OT NE cells are indeed active stem cells and that some of them exhibit long G2 phases. We identified several novel pathways (e.g., DNA repair pathways) potentially involved in NE cell homeostasis. In situ hybridization studies showed that all NE populations in the postembryonic medaka brain have a similar molecular signature. Our findings highlight the importance of NE progenitors in medaka and improve our understanding of NE-cell biology. These cells are potentially useful not only for neural stem cell studies but also for improving the characterization of neurodevelopmental diseases, such as microcephaly. Stem Cells 2017;35:1505-1518.