Specification of the Cerebellar Territory
The cerebellar primordium develops dorsally at an intermediate anteroposterior (AP) level of the neural tube. Its size is modulated by the early anteriorizing and posteriorizing signals, which pattern the neural tube. Two important signaling centers, the
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Specification of the Cerebellar Territory Marion Wassef
Abstract
The cerebellar primordium develops dorsally at an intermediate anteroposterior (AP) level of the neural tube. Its size is modulated by the early anteriorizing and posteriorizing signals, which pattern the neural tube. Two important signaling centers, the midbrain–hindbrain organizer and the roof plate, intersect at the level of the cerebellar anlage and control its positioning, differentiation, growth, survival, and patterning. Neural tube bending in the pontine region induces a widening of the fourth ventricle, which is made possible by choroid plexus differentiation and extension. As a consequence of these morphogenetic changes, the AP axis of the cerebellar primordium is rotated by 90 , and the cerebellar vermis and hemispheres derive from the anterior and posterior parts of the early cerebellar plate, respectively. The cerebellar plate is progressively subdivided along its dorsoventral axis into distinct domains, which generate subsets of cerebellar neurons according to their neurotransmitter phenotype. The roof plate marked by Gdf7 expression is at the origin of choroid plexus cells but does not contribute neurons or glia to the cerebellum. The rhombic lip, marked by Atoh1 expression, produces all the glutamatergic neurons of the cerebellum and a large number of non-cerebellar neurons. Finally, the ventral cerebellar neuroepithelium, marked by Ptf1a expression, generates all the GABAergic neurons and can be further subdivided into two progenitor domains, devoted to the production of Purkinje cells and GABAergic projection neurons of the deep
M. Wassef Institut de Biologie de l’Ecole Normale Supe´rieure (IBENS), 46 rue d’Ulm, 75005 Paris, France and CNRS UMR 8197, 46 rue d’Ulm, 75005 Paris, France and INSERM U1024, 46 rue d’Ulm, 75005 Paris, France e-mail: [email protected] M. Manto, D.L. Gruol, J.D. Schmahmann, N. Koibuchi, F. Rossi (eds.), Handbook of the Cerebellum and Cerebellar Disorders, DOI 10.1007/978-94-007-1333-8_1, # Springer Science+Business Media Dordrecht 2013
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M. Wassef
cerebellar nuclei. The so-called cerebellar primordium is not restricted to the production of cerebellar neurons but contributes to a large number of nuclei in the isthmic region.
Introduction The relative positions of the main brain subdivisions (Fig. 1.1) are established during development and have been conserved in the course of vertebrate evolution. The neural tube progressively differentiates into distinct regional identities resulting in local modifications of the growth and mechanical properties of the neuroepithelium and the formation of bulges called vesicles. In parallel, the different domains of the neuroepithelium evolve distinct competences to respond to adjacent or intrinsic signals. The forebrain, midbrain, and hindbrain vesicles, which form first, are known as the primary brain vesicles and become further subdivided later. The vesicles and intervening constrictions have often been used as stage-specific landmarks of early brain r
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