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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2009.12.017 Byline: Tomoya Nakatani, Minoru Kumai, Eri Mizuhara, Yasuko Minaki, Yuichi Ono Keywords: Lmx1a; Foxa2; Dopaminergic neuron; Floor plate cell; Red nucleus; Mesencephalon; Neuronal identity; Cell fate; Mouse Abstract: Mesencephalic dopaminergic (mesDA) neurons control movement and behavior, and their loss causes severe neurological disorders, such as Parkinson's disease. Recent studies have revealed that mesDA neurons originate from mesencephalic floor plate (FP) cells, which had been thought of as non-neurogenic organizer cells regulating regional patterning and axonal projections. Otx2 and its FP-specific downstream factor Lmx1a have been shown to be sufficient to confer neurogenic activity on FP cells and determine a mesDA fate. However, the mechanism underlying how these factors control mesDA development and how FP cells and mesDA neurons are coordinately specified are still largely unknown. In the present study, we obtained evidence that Lmx1a and Lmx1b cooperate with Foxa2 to specify mesDA neuron identity by gain-of-function approaches using transgenic mice. Lmx1a/b appeared to select a mesDA fate by suppressing red nucleus fate in the context of Foxa2-positive progenitors, at least in part, through repressing the Sim1-Lhx1 and Ngn1 pathways that inhibit proper mesDA differentiation. We also found that, in the mesencephalon, FP cell fate is primarily determined by Foxa2 with a supportive action of Lmx1a/b through repressing Nkx6.1, which inhibits FP cell differentiation. Thus, FP and mesDA identities are determined by distinct specification pathways, both of which are controlled by the same combination of transcription factors, Lmx1a/b and Foxa2, and, as a consequence, mesDA neurons are generated from mesencephalic FP cells. Author Affiliation: KAN Research Institute Inc., Kobe MI R&D Center, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan Article History: Received 1 July 2009; Revised 7 December 2009; Accepted 15 December 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2009.11.032 Byline: Eri Mizuhara (a), Yasuko Minaki (a), Tomoya Nakatani (a), Minoru Kumai (b), Takeshi Inoue (a), Keiko Muguruma (c), Yoshiki Sasai (c), Yuichi Ono (a)(b) Keywords: Neph3; E-cadherin; Ptf1a; Purkinje cell; Origin; Neuronal subtype; Cell sorting; Cell surface marker; Fate mapping Abstract: GABAergic Purkinje cells (PCs) provide the primary output from the cerebellar cortex, which controls movement and posture. Although the mechanisms of PC differentiation have been well studied, the precise origin and initial specification mechanism of PCs remain to be clarified. Here, we identified a cerebellar and spinal cord GABAergic progenitor-selective cell surface marker, Neph3, which is a direct downstream target gene of Ptf1a, an essential regulator of GABAergic neuron development. Using FACS, Neph3.sup.+ GABAergic progenitors were sorted from the embryonic cerebellum, and the cell fate of this population was mapped by culturing in vitro. We found that most of the Neph3.sup.+ populations sorted from the mouse E12.5 cerebellum were fated to differentiate into PCs while the remaining small fraction of Neph3.sup.+ cells were progenitors for Pax2.sup.+ interneurons, which are likely to be deep cerebellar nuclei GABAergic neurons. These results were confirmed by short-term in vivo lineage-tracing experiments using transgenic mice expressing Neph3 promoter-driven GFP. In addition, we identified E-cadherin as a marker selectively expressed by a dorsally localized subset of cerebellar Neph3.sup.+ cells. Sorting experiments revealed that the Neph3.sup.+ E-cadherin.sup.high population in the embryonic cerebellum defined PC progenitors while progenitors for Pax2.sup.+ interneurons were enriched in the Neph3.sup.+ E-cadherin.sup.low population. Taken together, our results identify two spatially demarcated subregions that generate distinct cerebellar GABAergic subtypes and reveal the origin of PCs in the ventricular zone of the cerebellar primordium. Author Affiliation: (a) Group for Neuronal Differentiation, KAN Research Institute Inc., Kobe, Hyogo 650-0047, Japan (b) Group for Transgenic Technology, KAN Research Institute Inc., Kobe, Hyogo 650-0047, Japan (c) Organogenesis and Neurogenesis Group, Center for Developmental Biology, RIKEN, Kobe, Hyogo 650-0047, Japan Article History: Received 30 July 2009; Revised 12 November 2009; Accepted 30 November 2009