Fig. 4

Asymmetric habenular neurogenesis is independent of the parapineal. (A,B) Confocal projection of immuno-detected HuC/D proteins in 36-38 hpf control (A) and parapineal-ablated (B) zebrafish embryos. Arrows indicate the habenula with the higher number of HuC/D⁺ neurons. The habenulae are indicated by a dashed white line, the epiphysis by a blue line. (A′,B′) ToPro nuclear staining of the embryos in A,B reveals the parapineal in the control (yellow) but not in the parapineal-ablated embryo; the epiphysis is shaded blue. (C) Numbers of left versus right HuC⁺ habenular neurons with each point representing one embryo. A symmetry line (black) is included as a reference. The dotted lines represent the best-fit linear regression for controls and ablated embryos. (D) Asymmetry index (AI, see Materials and methods) plotted for each control or parapineal-ablated embryo. The horizontal black lines indicate the median AI value for the group of like-treated embryos.