Fig. 1

Fig. 1 Epiphysial neurons are located in an accessible site. (A) Dorsal view of the head of a 28 hpf embryo showing that the epiphysial neurons are located at the base of the epiphysis. Anterior is up. Axons were labeled with an antibody against acetylated α-tubulin. The epiphysial axons on each side of the epiphysis (Ep), which is located at the dorsal midline, run laterally and ventrally to form the dorsoventral diencephalic tract (DVDT). Posterior to the DVDT is the posterior commissure (PC) that runs just anterior to the tectum (T). Scale is 50 μm. (B) Schematic diagram illustrating the rationale of the transplantation experiments on a dorsal view of the embryo. Axons of epiphysial neurons extend from the epiphysis (large circle at the midline) to pioneer the DVDT that extends along the surface of the diencephalon. The axons then turn anteriorly into the tract of the postoptic commissure (TPOC). The TPOC is pioneered by neurons (anterior cluster of circles) in the anterior and ventral diencephalon. The PC is pioneered by dorsally directed axons from neurons located in the anterior tegmentum (cluster of circles just medial to the eyes). The black circles with arrows and question marks represent ectopically transplanted epiphysial neurons and some of the possible directions that their axons could extend in the brain. (C) Schematic diagram illustrating the rationale of the transplantation experiments on a lateral view of the embryo. Anterior is to the right and dorsal is up.