Figure 1.

Comparison of oligodendrocyte progenitor cell (OPC) and astrocyte tiling behaviors. (A) OPCs migrate ventrally and dorsally from their origin in the ventral spinal cord motor neuron progenitor (pMN) domain. Astrocytes originate in the ventricular (VZ) and subventricular zones (SVZ) and migrate throughout the gray and white matter of the CNS. In the spinal cord, astrocytes migrate radially into separate domains. (B) OPCs divide and then are repelled from one another through CMR, leading to an equal spread across the neuropil. In astrocytes, pioneer astrocytes spread throughout the CNS and then clonally divide to cover the neuropil. (C) OPCs form their domains through CMR, during which contact between two OPCs leads to both OPCs retracting their processes and moving away from one another. This process occurs throughout the life of an OPC, leading to equilibrium. In contrast, immature astrocytes overlap extensively and then establish their domains over time. Astrocyte processes become more elaborately branched yet are more confined, suggesting some sort of retraction or pruning of processes.