Independent modes of ganglion cell translocation ensure correct lamination of the zebrafish retina

The arrangement of neurons into distinct layers is critical for neuronal connectivity and function of the nervous system. During development, most neurons move from their birthplace to the appropriate layer, where they polarize. However, kinetics and modes of many neuronal translocation events still await exploration. Here, we investigate ganglion cell (RGC) translocation across the embryonic zebrafish retina. After completing their translocation, RGCs establish the most basal retinal layer where they form the optic nerve. Using in toto light sheet microscopy, we show that somal translocation of RGCs is a fast and directed event. It depends on basal process attachment and stabilized microtubules. Interestingly, interference with somal translocation induces a switch to multipolar migration. This multipolar mode is less efficient but still leads to successful RGC layer formation. When both modes are inhibited, RGCs that fail to translocate induce lamination defects, indicating that correct RGC translocation is crucial for subsequent retinal lamination.