Fig. 7. Wnt attenuation modulates DA cell number at late gastrula stage. (A,B) Micrographs of DA neurons in 48-hpf zebrafish embryos that were injected with a Tol2 vector harboring dkk1 cDNA under the control of the heat-shock 70 promoter (hsp70::dkk1). (A) Embryos were incubated at the non-permissive temperature of 28.5°C for 48 hours. (B) Embryos were incubated at 28.5°C until 4 hpf and were then shifted to 37°C for 1 hour and thereafter grown at 28.5°C. Embryos were subjected (after 48 hours at 28.5°C) to in situ hybridization with a dat RNA probe. (C) Bar chart showing average cell counts of DA neurons in control and hsp70::dkk1-injected embryos. All embryos were subjected to a 1-hour temperature shock (37°C) at the indicated stages of development, as described above. The number of embryos analyzed (n) is shown beneath. Dien, diencephalon; Tel, telencephalon. Scale bar: 50 µm.