RESUMO
Rhou encodes a Cdc42-related atypical Rho GTPase that influences actin organization in cultured cells. In mouse embryos at early-somite to early-organogenesis stages, Rhou is expressed in the columnar endoderm epithelium lining the lateral and ventral wall of the anterior intestinal portal. During foregut development, Rhou is downregulated in regions where the epithelium acquires a multilayered morphology heralding the budding of organ primordia. In embryos generated from Rhou knockdown embryonic stem (ES) cells, the embryonic foregut displays an abnormally flattened shape. The epithelial architecture of the endoderm is disrupted, the cells are depleted of microvilli and the phalloidin-stained F-actin content of their sub-apical cortical domain is reduced. Rhou-deficient cells in ES cell-derived embryos and embryoid bodies are less efficient in endoderm differentiation. Impaired endoderm differentiation of Rhou-deficient ES cells is accompanied by reduced expression of c-Jun/AP-1 target genes, consistent with a role for Rhou in regulating JNK activity. Downregulation of Rhou in individual endoderm cells results in a reduced ability of these cells to occupy the apical territory of the epithelium. Our findings highlight epithelial morphogenesis as a required intermediate step in the differentiation of endoderm progenitors. In vivo, Rhou activity maintains the epithelial architecture of the endoderm progenitors, and its downregulation accompanies the transition of the columnar epithelium in the embryonic foregut to a multilayered cell sheet during organ formation.
Assuntos
Sistema Digestório/embriologia , Sistema Digestório/metabolismo , Proteínas rho de Ligação ao GTP/metabolismo , Actinas/metabolismo , Animais , Sequência de Bases , Diferenciação Celular , Linhagem Celular , Células-Tronco Embrionárias/citologia , Células-Tronco Embrionárias/metabolismo , Endoderma/citologia , Endoderma/embriologia , Endoderma/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Técnicas de Silenciamento de Genes , Células Hep G2 , Humanos , Junções Intercelulares/metabolismo , Junções Intercelulares/ultraestrutura , Camundongos , Camundongos Knockout , Células NIH 3T3 , RNA Interferente Pequeno/genética , Transdução de Sinais , Proteínas Wnt/metabolismo , Proteínas rho de Ligação ao GTP/antagonistas & inibidores , Proteínas rho de Ligação ao GTP/genéticaRESUMO
A report on the 15th International Society of Developmental Biologists Congress, Sydney, Australia, 3-7 September 2005.