Figure 11

Summary of distinct progenitor cell populations in the thalamus - a working hypothesis. Based on our observations, we propose a working hypothesis in which three types (types I, II, and III) of progenitor cells reside in the embryonic mouse thalamus. A to C denote the position of these progenitor cells at different phases of the cell cycle. Midline is to the left. The dashed line indicates the VZ/SVZ border. (A) Cells in S phase, most typically detected by a 0.5-hour EdU pulse. All the progenitor cell types comprise a single, wide column in the middle of the thalamus. (B) Cells in G2 phase, most typically detected by a 2-hour EdU pulse. RGs are moving towards the ventricle by interkinetic nuclear migration. (C) Cells in M phase. RGs divide at the ventricular surface, whereas type II and III cells (both are basal progenitor cells) divide away from the ventricle. Type II cells divide in the VZ and type III cells divide in the SVZ. (D) Hypothetical mode of cell division based on studies on neocortical IPCs. RGs divide asymmetrically to produce a RG and either a basal progenitor cell (1,2) or a neuron (3). Type II cells divide basally in the VZ and generate two neurons (4) or two type II cells (5). Type III cells divide basally in the SVZ and generate two neurons (6) or two type III cells (7). The actual lineage relationship between the three progenitor cell types in the thalamus is a topic of future investigation.