title: Regionalization of the isthmic and cerebellar primordia.
abstract: The complex migrations of neurons born in the dorsal neural tube of the isthmic and rhombomere l (rl) domains complicate the delineation of the cerebellar primordium. We show that Purkinje cells (P) are likely generated over a wide territory before gathering in the future cerebellar primordium under the developing external granular layer. Later expansion of the cerebellum over a restricted ependymal domain could rely on mutual interations between P cells and granule cell progenitors (GCP). P are attracted by GCP and in turn stimulate their proliferation, increasing the surface of the developing cortex. At later stages, regionalization of the developing and adult cerebellar cortex can be detected through regional variations in the distribution of several P cell markers. Whether and how the developmental and adult P subtypes are related is still unknown and it is unclear if they delineate the same sets of cerebellar subdivisions. We provide evidence that the early P regionalization is involved in intrinsic patterning of the cerebellar primordium, in particular it relate to the organization of the corticonuclear connection. We propose that the early P regionalization provides a scaffold to the mature P regionalization but that the development of functional afferent connections induces a period of P plasticity during which the early regional identity of P could be remodeled.
authors.affiliation: Régionalisation Nerveuse CNRS/ENS, UMR 8542, Ecole normale supérieure, 46 rue d'Ulm, 75005 Paris, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Narboux-Nême
authors.forename: Angeliki
authors.initials: A
authors.lastname: Louvi
authors.forename: Paula
authors.initials: P
authors.lastname: Alexandre
authors.forename: Marion
authors.initials: M
authors.lastname: Wassef
mesh_terms: D000818:Animals; D002525:Cerebellar Cortex / Q000166:cytology* / Q000196:embryology*; D006801:Humans; D009434:Neural Pathways / Q000166:cytology / Q000196:embryology; D011689:Purkinje Cells / Q000166:cytology* / Q000502:physiology*