title: Mesodiencephalic dopaminergic neuronal differentiation does not involve GLI2A-mediated SHH-signaling and is under the direct influence of canonical WNT signaling.
abstract: Sonic Hedgehog (SHH) and WNT proteins are key regulators in many developmental processes, like embryonic patterning and brain development. In the brain, SHH is expressed in a gradient starting in the floor plate (FP) progressing ventrally in the midbrain, where it is thought to be involved in the development and specification of mesodiencephalic dopaminergic (mdDA) neurons. GLI2A-mediated SHH-signaling induces the expression of Gli1, which is inhibited when cells start expressing SHH themselves. To determine whether mdDA neurons receive GLI2A-mediated SHH-signaling during differentiation, we used a BAC-transgenic mouse model expressing eGFP under the control of the Gli1 promoter. This mouse-model allowed for mapping of GLI2A-mediated SHH-signaling temporal and spatial in the mouse midbrain. Since mdDA neurons are born from E10.5, peaking at E11.0-E12.0, we examined Gli1-eGFP embryos at E11.5, E12.5, and E13.5, indicating whether Gli1 was induced before or during mdDA development and differentiation. Our data indicate that GLI2A-mediated SHH-signaling is not involved in mdDA neuronal differentiation. However, it appears to be involved in the differentiation of neurons which make up a subset of the red nucleus (RN). In order to detect whether mdDA neuronal differentiation may be under the control of canonical WNT-signaling, we used a transgenic mouse-line expressing LacZ under the influence of stable β-catenin. Here, we show that TH+ neurons of the midbrain receive canonical WNT-signaling during differentiation. Therefore, we suggest that early SHH-signaling is indirectly involved in mdDA development through early patterning of the midbrain area, whereas canonical WNT-signaling is directly involved in the differentiation of the mdDA neuronal population.
authors.affiliation: Swammerdam Institute for Life Sciences, CNS, FNWI University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Simone
authors.initials: S
authors.lastname: Mesman
authors.affiliation: Swammerdam Institute for Life Sciences, CNS, FNWI University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Lars
authors.initials: L
authors.lastname: von Oerthel
authors.affiliation: Swammerdam Institute for Life Sciences, CNS, FNWI University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Marten P
authors.initials: MP
authors.lastname: Smidt
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D059290:Dopaminergic Neurons / Q000166:cytology* / Q000378:metabolism; D004622:Embryo, Mammalian / Q000166:cytology* / Q000378:metabolism; D005260:Female; D053823:Hedgehog Proteins / Q000378:metabolism*; D006801:Humans; D007124:Immunoenzyme Techniques; D017403:In Situ Hybridization; D051741:Kruppel-Like Transcription Factors / Q000502:physiology*; D008636:Mesencephalon / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D055495:Neurogenesis / Q000502:physiology; D051153:Wnt Proteins / Q000378:metabolism*; D000075746:Zinc Finger Protein Gli2
chemical_list: C000618551:Gli2 protein, mouse; D053823:Hedgehog Proteins; D051741:Kruppel-Like Transcription Factors; C465570:Shh protein, mouse; D051153:Wnt Proteins; D000075746:Zinc Finger Protein Gli2