Zebrafish pax6b is expressed in endocrine pancreatic cells in contrast to the zebrafish pax6a gene. (A, B) At 24 hours of development, both pax6a and pax6b mRNAs are detected by in situ hybridization in the eye and in the telencephalon but only pax6b is expressed in the pancreas. (C-D') At 48 hours post fertilization (hpf), pax6a and pax6b are expressed in overlapping areas, such as the ocular stuctures (retina and lens), the ventral telencephalon and the diencephalon. pax6a is detected more strongly in the hindbrain whereas only pax6b is expressed in the pancreatic endocrine islet. (E) pax6b colocalizes with neurod in the differentiating endocrine cells by 30 hpf. (F) No pancreatic expression of pax6a is detected at 48 hpf, as demonstrated by double WISH with pax6a and pdx1. (G-R) Double fluorescent in situ hybridizations on 30 hpf zebrafish embryos show pax6b colocalization with the four major hormones glucagon, insulin, somatostatin and ghrelin. Abbreviations: e, eye; gcg, glucagon; ghrl, ghrelin; hb, hindbrain; ins, insulin; p, pancreas; sst, somatostatin; tc, telencephalon. Embryos in figures A-R are presented in a ventral view, anterior to the left. Embryos in C'-D' are presented in a lateral view, anterior to the left.