Abstract
BackgroundIn the cerebellum of newborn S100B-EGFP mice, we had previously noted the presence of a large population of S100B-expressing cells, which we assumed to be immature Bergmann glial cells. In the present study, we have drawn on this observation to establish the precise spatio-temporal pattern of S100B gene expression in the embryonic cerebellum.ResultsFrom E12.5 until E17.5, S100B was expressed in the primary radial glial scaffold involved in Purkinje progenitor exit from the ventricular zone and in the Sox9+ glial progenitors derived from it. During the same period coinciding with the primary phase of granule neuron precursor genesis, transient EGFP expression tagged the Pax6+ forerunners of granule precursors born in the cerebellar rhombic lip.ConclusionThis study provides the first characterization of S100B-expressing cell types of the embryonic mouse cerebellum in a high-resolution map. The transient activation of the S100B gene distinguishes granule neuron precursors from all other types of precursors so far identified in the rhombic lip, whereas its activation in radial glial precursors is a feature of Bergmann cell gliogenesis.
Highlights
In the cerebellum of newborn S100B-EGFP mice, we had previously noted the presence of a large population of S100B-expressing cells, which we assumed to be immature Bergmann glial cells
At around E17.5, and compared to other regions of the brain, a relatively high level of the S100B-EGFP reporter protein was found in the Cb primordium (Fig 1A), and this was matched by a fair level of S100B protein expression in densely packed radial glial cells located at the midbrain-hindbrain boundary (Fig 1B, MHB) or bordering the fourth ventricle (Fig 1C), in isolated cells of the cortical transitory zone (Fig 1D), and to a lesser extent in the rhombic lip (RL) (Fig 1E)
Our results establish the S100B protein as a marker of the brain lipid binding protein (BLBP)+ Sox9+ primary radial glial scaffold starting on E13.5
Summary
In the cerebellum of newborn S100B-EGFP mice, we had previously noted the presence of a large population of S100B-expressing cells, which we assumed to be immature Bergmann glial cells. Using a line of transgenic mice in which tamoxifen-inducible Cre expression at the time of birth results in permanent β-galactosidase labeling, RL precursors destined to populate the internal granule layer (IGL) were estimated to be generated in a rostral-to-caudal sequence between E13 and E17 [6]. At the time, these Lac-Z-labelled IGL cells were thought to represent a homogenous population of granule neurons. At E11.5, they stream over the entire dorsal surface of the Cb, and from E12.5 until E14.5 they aggregate in the NTZ, a transient zone of differentiation [6,8,9]
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