Fig. 4

PARK7^-/- larvae have a lower number of dopaminergic neurons compared to wild types. Zebrafish were exposed to 500 µM MPP⁺ or vehicle from 3 to 5 dpf, thereafter fixed, bleached, whole-mount immune-stained using anti-tyrosine hydroxylase and mounted in clearing solution. Larvae were imaged by confocal microscopy. (A) Dopaminergic cell populations at 5 dpf. Cells of interest are encircled with a dotted line. Colours refer to the stack level. (B) Circled cell population from (A) after selecting stack images of interest corresponding to DC1 and DC2 populations. (C) Schematic sagittal section of the 5 dpf brain showing the location of the DC1 and DC2 dopaminergic cell populations from a lateral view. (D) Projections of dopaminergic neurons in the selected DC1 and part of DC2 population from wild type, wild type + MPP⁺, PARK7^-/- , and PARK7^-/- + MPP⁺ at 5 dpf. Arrows point to the larger pear formed DC2 dopaminergic neurons. (E) The number of dopaminergic cells in the DC1 population at 3, 4, and 5 dpf. Numbers are the mean ± SEM from 3 to 6 (n = 3–6 larvae). **p < 0.01, ***p < 0.001 using Type II ANOVA and Tuckey-adjusted pairwise comparisons. Bars, 50 µm. Dopaminergic cell populations are named according to Rink and Wulliman³⁴, which corresponds to MPP⁺ responsive cell populations (5, 6, and 11) as shown in Sallinen et al.⁹.