Canonical and noncanonical Wnt signaling regulate crucial events in the development of vertebrates and invertebrates. In this work we show that vertebrate Diversin, a potential orthologue of Drosophila Diego, controls fusion of heart precursors and gastrulation movements in zebrafish embryogenesis. These events are regulated by noncanonical Wnt signaling, which is independent of -catenin. We found that Diversin directly interacts with Dishevelled and that this interaction is necessary and sufficient to mediate signals of the noncanonical Wnt pathway to downstream effectors like Rho family GTPases and Jun N-terminal kinase. The ankyrin repeats of Diversin are required for the interaction with Dishevelled, for the activation of noncanonical Wnt signaling, and for the biological responses. The mutation K446M in the DEP domain of vertebrate Dishevelled, which mimics a classical Drosophila loss of function mutation, prevents functional interaction with Diversin's ankyrin repeats. Diversin also affects planar cell polarity in Drosophila, which is controlled by the noncanonical Wnt signaling pathway. Our data thus demonstrate that Diversin and Dishevelled function together in a mutually dependent fashion in zebrafish gastrulation and organ formation.convergence and extension ͉ Dishevelled ͉ embryogenesis ͉ noncanonical Wnt signaling ͉ Rho family GTPases
Multidrug resistance proteins (Mrps) are ATP-driven export pumps which mediate the export of organic anions such as glutathione conjugates and glucuronides from eukaryotic cells. Within the central nervous system astrocytes have important functions in metabolism and detoxification. In such processes Mrps play essential roles. To identify the Mrp repertoire of mouse brain and of astrocytes in particular, the expression of six mouse Mrps was investigated by reverse-transcription polymerase-chain reaction (RT-PCR). Using mouse brain mRNA as source, amplification products were obtained for Mrp1, Mrp3, Mrp4, Mrp5 and Mrp6. In contrast, mRNA of Mrp2 could not be detected in mouse brain. To investigate whether individual astrocytes express different Mrps in brain, single-cell RT-PCRs were performed from the cytosol harvested from single astrocytes in acutely isolated brain slices from cortex and cerebellum of TgN(GFAP-EGFP) mice. In these mice astrocytes can readily be identified by glial fibrillary acidic protein promoter-controlled green fluorescent protein expression. Investigation of individual cortical astrocytes and Bergmann glial cells revealed that these cells express Mrp1, Mrp4 and Mrp5 and that individual astrocytes can contain mRNA of one, two or three of these Mrps simultaneously.
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