Pax6 Influences the Time and Site of Origin of Glial Precursors in the Ventral Neural Tube

Abstract

Neuroepithelial precursors in the ventral ventricular zone (VZ) of the spinal cord generate motor neurons (MNs) and interneurons, and then a subset of precursors starts to produce oligodendrocyte progenitors (OLPs). We show that OLPs originate in the ventral-most part of thePax6-positive VZ, which at earlier times generates somatic (Isl2/Lim3-positive) MNs. InSmall eye(Pax6-deficient) mice, the origin of OLPs is shifted dorsally and both OLPs andIsl2/Lim3MNs are delayed. We suggest that somatic MNs and OLPs are generated sequentially from a common set of MN-OL precursors whose position in the VZ is influenced by Pax6. Neuron–glia fate switching might be a preprogrammed property of these precursors or a response to feedback from newly generated neurons. OLs developed normally in explants ofIsl1(−/−)spinal cords, which lack MNs, arguing against feedback control and suggesting that the neuron–glia switch is an intrinsic developmental program in a specific subset of neural precursors.