RESUMO
Frizzled (Fz) signaling regulates cell polarity in both vertebrates and invertebrates. In Drosophila, Fz orients the asymmetric division of the sensory organ precursor cell (pI) along the antero-posterior axis of the notum. Planar polarization involves a remodeling of the apical-basal polarity of the pI cell. The Discs-large (Dlg) and Partner of Inscuteable (Pins) proteins accumulate at the anterior cortex, while Bazooka (Baz) relocalizes to the posterior cortex. Dlg interacts directly with Pins and regulates the localization of Pins and Baz. Pins acts with Fz to localize Baz posteriorly, but Baz is not required to localize Pins anteriorly. Finally, Baz and the Dlg/Pins complex are required for the asymmetric localization of Numb. Thus, the Dlg/Pins complex responds to Fz signaling to establish planar asymmetry in the pI cell.
Assuntos
Padronização Corporal , Proteínas de Ciclo Celular , Polaridade Celular , Proteínas de Drosophila , Drosophila melanogaster/citologia , Drosophila melanogaster/embriologia , Proteínas de Insetos/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular , Células-Tronco/citologia , Proteínas Supressoras de Tumor , Animais , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Divisão Celular , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Receptores Frizzled , Imuno-Histoquímica , Proteínas de Insetos/genética , Hormônios Juvenis/metabolismo , Substâncias Macromoleculares , Proteínas de Membrana/fisiologia , Modelos Biológicos , Mutação/genética , Neurônios/citologia , Neurônios/metabolismo , Testes de Precipitina , Ligação Proteica , Proteína Quinase C/metabolismo , Transporte Proteico , Receptores Acoplados a Proteínas G , Proteínas Recombinantes de Fusão/metabolismo , Transdução de Sinais , Células-Tronco/metabolismoRESUMO
Asymmetric cell division generates daughter cells with different developmental fates. In Drosophila neuroblasts, asymmetric divisions are characterized by (1) a difference in size between the two daughter cells and (2) an asymmetric distribution of cell fate determinants, including Prospero and Numb, between the two daughter cells. In embryonic neuroblasts, the asymmetric localization of cell fate determinants is under the control of the protein Inscuteable (Insc), which is itself localized asymmetrically as an apical crescent. Here, we describe a new Drosophila protein, Rapsynoid (Raps), which interacts in a two-hybrid assay with the signal transduction protein Galpha(i). We show that Raps is localized asymmetrically in dividing larval neuroblasts and colocalizes with Insc. Moreover, in raps mutants, the asymmetric divisions of neuroblasts are altered: (1) Insc is no longer asymmetrically localized in the dividing neuroblast; and (2) the neuroblast division produces two daughter cells of similar sizes. However, the morphologically symmetrical divisions of raps neuroblasts still lead to daughter cells with different fates, as shown by differences in gene expression. Our data show that Raps is a novel protein involved in the control of asymmetric divisions of neuroblasts.
