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Fig. 3 Proliferation and neurogenesis rapidly decrease at juvenile stages and is severely reduced in the adult zebrafish SAG. (A,B) Antibody staining showing proliferation (PCNA), neurod:GFP-positive cells and mature neurons (HuC/D) in the SAG of juvenile (2 and 3 months) and adult (8 and 20 months) neurod:GFP zebrafish. (A) At juvenile stages, neurod:GFP-positive cells proliferate (neurod:GFP/PCNA-positive cells, solid arrowheads) and give rise to new neurons (neurod:GFP/HuC/D-positive cells, arrows). In contrast, neurod:GFP-positive cells (open arrowheads) are not proliferating in adult fish and neurod:GFP/HuC/D-positive cells are rarely found. (B) Proliferating PCNA-positive but neurod:GFP-negative cells (arrowheads) can be found in the vicinity of the neurod:GFP-positive population at all stages. Panels on right show magnification of boxed areas in left panels. (C-G) Quantification of antibody staining. The overall number of PCNA-positive cells (C), the overall number of neurod:GFP-positive cells (D) and neurod:GFP/PCNA-positive cells (E) significantly decrease from 2 to 3 months, leaving only few PCNA-positive cells but no neurod:GFP/PCNA-positive cells at 8 months. (F) The number of newborn neurons marked by neurod:GFP and HuC/D decreases significantly from 2 to 3 and further from 3 to 8 months. (G) The number of cells in the neurod:GFP-positive pool that are neither proliferating nor positive for HuC/D stays constant over time. Scale bars: 50 µm. Cross-sections show dorsal to the top and lateral to the right. For quantifications: 2 months, n=3; 3 months, n=3; adult, n=4 (n=fish; 1 SAG/fish; 12 sections/SAG); data are presented as mean±s.e.m. Ordinary one-way ANOVA with Tukey's multiple comparison test. *P≤0.05; **P≤0.01; ***P≤0.001.