Ikaros-1 couples cell cycle arrest of late striatal precursors with neurogenesis of enkephalinergic neurons.

During central nervous system development, several transcription factors regulate the differentiation of progenitor cells to postmitotic neurons. Here we describe a novel role for Ikaros-1 in the generation of late-born striatal neurons. Our results show that Ikaros-1 is expressed in the boundary of the striatal germinal zone (GZ)/mantle zone (MZ), where it induces cell cycle arrest of neural progenitors by up-regulation of the cyclin-dependent kinase inhibitor (CDKi) p21(Cip1/Waf1). This effect is coupled with the neuronal differentiation of late precursors, which in turn is critical for the second wave of striatal neurogenesis that gives rise to matrix neurons. Consistently, Ikaros(-/-) mice had fewer striatal projecting neurons and, in particular, enkephalin (ENK)-positive neurons. In addition, overexpression of Ikaros-1 in primary striatal cultures increases the number of calbindin- and ENK-positive neurons. Our results also show that Ikaros-1 acts downstream of the Dlx family of transcription factors, insofar as its expression is lost in Dlx1/2 double knockout mice. However, we demonstrate that Ikaros-1 and Ebf-1 independently regulate the final determination of the two populations of striatal projection neurons of the matrix compartment, ENK- and substance P-positive neurons. In conclusion, our findings identify Ikaros-1 as a modulator of cell cycle exit of neural progenitors that gives rise to the neurogenesis of ENK-positive striatal neurons.We thank M.T. Mun ̃oz, A. Lo ́pez, T. Gil, and M. Bonete for technical support and Dr. Maria Calvo and Anna Bosch from the confocal microscopy unit at the Serveis Cientı ́fico-Te`cnics (Universitat de Barcelona) for their sup-port and advice on confocal techniques. We also thank Dr.K. Campbell for providing Dlx5/6Cre-IRES-EGFP trans-genic mice, Dr. Rudolf Grosschedl for Ebf1–/– mice, and Dr.Susan Winandy for Ikaros constructs. We are also very grateful to Robin Rycroft for the English language revisionS

Application de la cytométrie de flux aux cellules du système nerveux central et recherche de nouveaux marqueurs pour les cellules souches neurales

Les cellules souches neurales (CSN), cellules multipotentes ayant conservé une forte capacité proliférative, ouvrent de nouvelles perspectives dans le traitement des maladies neurodégénératives. Toutefois, leur meilleure caractérisation et la maîtrise de leur différenciation restent des problèmes fondamentaux. Cette thèse a eu pour objectif la recherche de marqueurs extracellulaires spécifiques des CSN permettant leur purification. Le premier point a été d'adapter l'analyse phénotypique par cytométrie de flux aux cellules du système nerveux central (SNC) puis de contrôler la fiabilité de marqueurs comme la nestine utilisée pour définir les CSN. Nous avons ensuite analysé l'expression de différents marqueurs type CD (cluster of differenciation) par les cellules présentes dans des cultures de CSN, d'astrocytes et de neurones. Nous avons montré que quelques marqueurs étaient majoritairement exprimés par ces cellules et qu'une sélection négative par CD3 permettrait un enrichissement en CSN.Neural stem cells (NSC) are of great interest for restorative strategies in neurodegenerative diseases because of their capacity to proliferate and to give rise to all of the major cell types of the central nervous system (CNS). However, major improvements in the characterisation and control of the differentiation of NSC are necessary. Our objectives were to search for specific extracellular markers of NSC in order to be able to identify and to sort them from amongst other cell types. First we investigated the possibility of using flow cytometry to characterise CNS-derived cells and then to control the specificity of markers such as nestin used to define NSC. Next, we evaluated the expression of a number of CD molecules (cluster of differentiation) by cells present in cultures of NSC, astrocytes and neurons. The results showed that some markers are differentially expressed by these cells and that a negative selection by CD3 would enable enrichment of NSC.NANTES-BU Médecine pharmacie (441092101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

AUF1 and Hu proteins in the developing rat brain: Implication in the proliferation and differentiation of neural progenitors

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