Heterogeneity in Progenitor Cell Subtypes in the Ventricular Zone of the Zebrafish Adult Telencephalon MARTIN M € ARZ, 1 PRISCA CHAPOUTON, 2 NICOLAS DIOTEL, 3 COLETTE VAILLANT, 3 BIRGIT HESL, 2 MASANARI TAKAMIYA, 1 CHEN SOK LAM, 1 OLIVIER KAH, 3 LAURE BALLY-CUIF, 2 * AND UWE STR € AHLE 1 * 1 Institute for Toxicology and Genetics, Forschungszentrum Karlsruhe in the Helmholtz Association, Karlsruhe Institute of Technology, Postfach 3640, 76021 Karlsruhe, Germany 2 HelmholtzZentrum M€ unchen, Department Zebrafish Neurogenetics, Institute of Developmental Genetics, Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany 3 Neurogenesis and Estrogens, UMR CNRS 6026, Universit  e de Rennes 1, 35042 Rennes, France KEY WORDS radial glia; neural stem cells; adult neurogenesis ABSTRACT The zebrafish has become a new model for adult neurogene- sis, owing to its abundant neurogenic areas in most brain subdivisions. Radial glia-like cells, actively proliferating cells, and label-retaining progenitors have been described in these areas. In the telencephalon, this complexity is enhanced by an organization of the ventricular zone (VZ) in fast and slow-dividing domains, suggesting the existence of heterogeneous progenitor types. In this work, we studied the expression of various transgenic or immunocytochemi- cal markers for glial cells (gfap:gfp, cyp19a1b:gfp, BLBP, and S100b), progenitors (nestin:gfp and Sox2), and neuro- blasts (PSA-NCAM) in cycling progenitors of the adult zebrafish telencephalon (identified by expression of prolifer- ating cell nuclear antigen (PCNA), MCM5, or bromodeox- yuridine incorporation). We demonstrate the existence of distinct populations of dividing cells at the adult telence- phalic VZ. Progenitors of the overall slow-cycling domains express high levels of Sox2 and nestin:gfp as well as all glial markers tested. In contrast, domains with an overall fast division rate are characterized by low or missing expression of glial markers. PCNA-positive cells in fast domains further display a morphology distinct from radial glia and co-express PSA-NCAM, suggesting that they are early neuronal precursors. In addition, the VZ contains cycling progenitors that express neither glial markers nor nestin:gfp, but are positive for Sox2 and PSA-NCAM, iden- tifying them as committed neuroblasts. On the basis of the marker gene expression and distinct cell morphologies, we propose a classification for the dividing cell states at the zebrafish adult telencephalic VZ. V V C 2010 Wiley-Liss, Inc. INTRODUCTION The adult mammalian brain harbors two regions of constitutive neurogenesis, the subependymal zone (SEZ) of the lateral wall of the lateral ventricle and the sub- granular zone (SGZ) of the dentate gyrus in the hippo- campus, from where neural stem cells (NSCs) with astrocytic features give rise to new neurons (Alvarez- Buylla and Garcia-Verdugo, 2002; Doetsch and Hen, 2005; Garcia et al., 2004; Goldman, 2003; Kempermann, 2002; Lledo and Saghatelyan, 2005; Merkle et al., 2004; Taupin and Gage, 2002). The function of these adult- born neurons is only beginning to be understood, but is likely to be fundamental to behavioral modulations. Adult NSCs in the mouse have been intensively charac- terized. Recent evidence suggests that, in the SEZ, they originate from embryonic radial glial cells, which act as NSCs during brain development (Doetsch, 2003; Gold- man, 2003; Gotz et al., 2002). These give rise to ependymal cells and astrocytes in postnatal stages, and a subpopulation of the latter retains NSC potential (Alvarez-Buylla and Lim, 2004; Doetsch, 2003; Spassky et al., 2005). Stem cells (also called B cells) in the mouse SEZ generate transit-amplifying progenitors (C cells), which proliferate to generate neuroblasts (A cells) that migrate along the rostral migratory stream (RMS) to the olfactory bulbs (OB) where they differentiate into interneurons (Doetsch and Alvarez-Buylla, 1996; Doetsch et al., 1997, 1999; Lois et al., 1996; Luskin, 1993; Peretto et al., 1997; Yang, 2008). A comparable scheme has been proposed in the SGZ, where adult neurogenesis originates from radial glia-like stem cells (Type 1 cells) through a proliferating stage (Type 2 cells) generating neuroblasts (Type 3 cells) and dentate granule interneurons (Seri et al., 2001, 2004; Steiner et al., 2006). These categorizations have been instrumental in addressing the molecular and cellular mechanisms of neurogenesis in the adult brain. In contrast to the limited neurogenic capability of adult mammals, teleosts such as the zebrafish show a Additional Supporting Information may be found in the online version of this article. Grant sponsors: Forschungszentrum Karlsruhe and HMGU in the Helmholtz Asso- ciation; Grant sponsor: European commission IP ZF-MODELS; Grant number: LSHC- CT-2003-503466; Grant sponsors: IP EUTRACC, CNRS, MRT, ANBR Need, Center for Protein Science Munich, Volkswagen Association, and the Life Science Stiftung. Chen Sok Lam is currently at Neural Stem Cell Laboratory, Institute of Medical Biology, A-TAR, Singapore 138648. Laure Bally-Cuif is currently at Team Zebrafish Neurogenetics, Laboratory of Neurobiology and Development, Institute of Neurobiology Alfred Fessard, CNRS UPR3294, Avenue de la Terrasse, 91198 Gif-sur-Yvette, France *Correspondence to: Uwe Str€ ahle, Institute for Toxicology and Genetics, For- schungszentrum Karlsruhe in the Helmholtz Association, Karlsruhe Institute of Technology, Postfach 3640, 76021 Karlsruhe, Germany. E-mail: uwe.straehle@ itg.fzk.de or Laure Bally-Cuif HelmholtzZentrum M€ unchen, Department Zebrafish Neurogenetics, Institute of Developmental Genetics, Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany. E-mail: bally@helmholtz-muenchen.de Received 6 July 2009; Accepted 23 December 2009 DOI 10.1002/glia.20971 Published online 12 February 2010 in Wiley InterScience (www.interscience. wiley.com). GLIA 58:870–888 (2010) V V C 2010 Wiley-Liss, Inc.