RESUMO
Complex regulatory networks regulate stem cell behavior and contributions to tissue growth, repair, and homeostasis. A full understanding of the networks controlling stem cell self-renewal and differentiation, however, has not yet been realized. To systematically dissect these networks and identify their components, we performed an unbiased, transcriptome-wide in vivo RNAi screen in female Drosophila germline stem cells (GSCs). Based on characterized cellular defects, we classified 646 identified genes into phenotypic and functional groups and unveiled a comprehensive set of networks regulating GSC maintenance, survival, and differentiation. This analysis revealed an unexpected role for ribosomal assembly factors in controlling stem cell cytokinesis. Moreover, our data show that the transition from self-renewal to differentiation relies on enhanced ribosome biogenesis accompanied by increased protein synthesis. Collectively, these results detail the extensive genetic networks that control stem cell homeostasis and highlight the intricate regulation of protein synthesis during differentiation.
Assuntos
Diferenciação Celular , Drosophila melanogaster/citologia , Células Germinativas/citologia , Biogênese de Organelas , Biossíntese de Proteínas , Ribossomos/metabolismo , Células-Tronco/citologia , Animais , Nucléolo Celular/patologia , Sobrevivência Celular/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Complexos Endossomais de Distribuição Requeridos para Transporte/metabolismo , Fator de Iniciação 4E em Eucariotos/metabolismo , Regulação da Expressão Gênica , Técnicas de Silenciamento de Genes , Genes de Insetos , Hipertrofia , Iniciação Traducional da Cadeia Peptídica/genética , Fenótipo , Ligação Proteica , Interferência de RNA , Transcriptoma/genéticaRESUMO
The differentiation of stem cells is a tightly regulated process essential for animal development and tissue homeostasis. Through this process, attainment of new identity and function is achieved by marked changes in cellular properties. Intrinsic cellular mechanisms governing stem cell differentiation remain largely unknown, in part because systematic forward genetic approaches to the problem have not been widely used. Analysing genes required for germline stem cell differentiation in the Drosophila ovary, we find that the mitochondrial ATP synthase plays a critical role in this process. Unexpectedly, the ATP synthesizing function of this complex was not necessary for differentiation, as knockdown of other members of the oxidative phosphorylation system did not disrupt the process. Instead, the ATP synthase acted to promote the maturation of mitochondrial cristae during differentiation through dimerization and specific upregulation of the ATP synthase complex. Taken together, our results suggest that ATP synthase-dependent crista maturation is a key developmental process required for differentiation independent of oxidative phosphorylation.
Assuntos
Diferenciação Celular , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/enzimologia , Mitocôndrias/enzimologia , ATPases Mitocondriais Próton-Translocadoras/metabolismo , Oócitos/enzimologia , Fosforilação Oxidativa , Animais , Animais Geneticamente Modificados , Linhagem Celular , Bases de Dados Genéticas , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Drosophila melanogaster/ultraestrutura , Genótipo , Microscopia Confocal , Microscopia de Fluorescência , Mitocôndrias/ultraestrutura , ATPases Mitocondriais Próton-Translocadoras/genética , Oócitos/ultraestrutura , Fenótipo , Multimerização Proteica , Interferência de RNA , Transdução de Sinais , Transfecção , Regulação para CimaRESUMO
Trans-epithelial migration describes the ability of migrating cells to cross epithelial tissues and occurs during development, infection, inflammation, immune surveillance, wound healing and cancer metastasis. Here we investigate Drosophila primordial germ cells (PGCs), which migrate through the endodermal epithelium. Through live imaging and genetic experimentation we demonstrate that PGCs take advantage of endodermal tissue remodeling to gain access to the gonadal mesoderm and are unable to migrate through intact epithelial tissues. These results are in contrast to the behavior of leukocytes, which actively loosen epithelial junctions to migrate, and raise the possibility that in other contexts in which migrating cells appear to breach tissue barriers, they are actually exploiting existing tissue permeability. Therefore, the use of active invasive programs is not the sole mechanism to infiltrate tissues.
Assuntos
Movimento Celular , Drosophila melanogaster/citologia , Drosophila melanogaster/crescimento & desenvolvimento , Endoderma/crescimento & desenvolvimento , Epitélio/crescimento & desenvolvimento , Células Germinativas/citologia , Morfogênese , Animais , Padronização Corporal , Endoderma/citologia , Migração Transendotelial e TransepitelialRESUMO
Signalling through Frizzled (Fz)/planar cell polarity (PCP) is a conserved mechanism that polarizes cells along specific axes in a tissue. Genetic screens in Drosophila melanogaster pioneered the discovery of core PCP factors, which regulate the orientation of hairs on wings and facets in eyes. Recent genetic evidence shows that the Fz/PCP pathway is conserved in vertebrates and is crucial for disparate processes as gastrulation and sensory cell orientation. Fz/PCP signalling depends on complex interactions between core components, leading to their asymmetric distribution and ultimately polarized activity in a cell. Whereas several mechanistic aspects of PCP have been uncovered, the global coordination of this polarization remains debated.
