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Source: http://www.neuro.mpg.de/Neuronal_Specification/ Date: september 1999 Max Planck Society, Department of Neuronal Specification, Head of Group: Magdalena Götz, Ph.D. How do precursor cells differ and how do they generate different cell types? General The adult brain is composed of distinct brain regions that perform highly specific functions and contain different types of neurons. How is this achieved during development? Why are different types of neurons generated at different positions, i.e. in prospective brain regions? We address this question in the forebrain, asking which mechanisms help to specify neurons in the cortex different from those in the striatum. The profound differences between these regions provide a well suited experimental system. The cerebral cortex contains mostly glutamatergic neurons arranged in different layers, whereas the ventrally adjacent region, the striatum, contains mostly GABAergic neurons that are arranged in a patch-matrix fashion. We examine how the precursor cells underlying the prospective cortex and striatum differ from each other and how these regional differences are translated in the generation of different cell types. Main approaches Cell fate analysis The genetic mechanisms involved in the specification of precursor cells are analyzed by the use of replication-incompetent retroviral vectors. This technique enables us to introduce genes in individual precursor cells and all their descendents allowing the analysis of cell types generated by an individual precursor cells. Fig. 1 depicts such a clone of cells derived from a single precursor cell. In this case all the descendents of a single precursor cell are glutamatergic neurons. To adress which factors instruct the generation of particular cell types we use co-expression retroviral vectors that express a homeobox transcription factor and a marker gene allowing gene manipulation and analysis of cell fate at the same time. In addition cell fate is examined by different in vitro approaches, e.g. FACS sorting of subsets of precursor cells and their subsequent manipulation in vitro. Region-specific migration of neurons When precursor cells generate postmitotic neurons the latter migrate along radial glia cells to their final position. Our recent data have shown a role of Pax6 for the proper specification of radial glia cells (coll. with A.Stoykova, P.Gruss), implying that radial glia cells are specified differentially in distinct brain regions. Indeed, Fig. 2 shows morphological differences between radial glia cells from the cortex and the striatum. Using in vitro assays and transgenic mice we analyze how radial glia are specified. In addition we manipulate gene expression in radial glia cells to characterize the molecular events involved in their specification and the regulation of neuronal migration. Region-specific adhesion Several lines of evidence suggest that the local environment plays an important role in the specification of cell fate. We have recently discovered a mechanism that seems to contribute to isolate cells in particular regions, i.e. specific environments. An in vitro adhesion assay revealed adhesive differences between cells from adjacent brain regions. Fig. 3 E-H depicts such an aggregate where cortical and striatal cells isolated at early neurogenesis have segregated from each other. Interestingly this selective adhesions seems influenced by members of the homeobox transcription factor family: In the Pax6-/- mice cortico-striatal segregation is abolished (Fig. 3A-D; coll. with A.Stoykova, P.Gruss). We are currently using viral vectors to examine the responsible adhesion molecules and their potential regulation by transcription factors. Finally we want to determine the consequences of selective adhesion for the delineation of brain regions. ---------------------------------------------------------------------- To sign-off Parkinsn send a message to: mailto:[log in to unmask] In the body of the message put: signoff parkinsn