Fig. 9. Summary diagram showing the process of nucleogenesis by PC neurons. All subsets of PC neurons show two distinct phases of migration, tangential and radial. (A) PGN/RTN neurons first migrate tangentially along the ventral margin of the metencephalon. They then migrate towards the ventricle, either before or after crossing the midline. In this phase, they migrate along nestin-positive radial fibres (red and grey). On arrival at their final destination, they stop migration and extend several dendrite-like processes (violet). In the myelencephalon (B), ECN and LRN neurons also initially execute tangential migration and cross the midline. They then migrate along radial fibres towards their final positions, as do PGN/RTN neurons. We hypothesize that PC neurons acquire responsiveness to transition-inducing cues expressed by radial fibres in specific locations (shown in red) and this acquisition takes place in a time-dependent manner (see changes in colour of migrating cells from green to dark blue).