negr1 and opcml expression at early developmental stages. 16-cell stage zebrafish embryos expressing negr1 (A) and opcml (B); sense probe stains are shown in the insets. (C,D) show lateral views of 12 hpf old embryos. negr1 is expressed in the midbrain and the otic placodes (C), while opcml exhibits ubiquitous expression (D). RT-PCR corroborates the presence of negr1 and opcml transcripts at the 16-cell stage (E). MB, midbrain; OP, otic placodes.

Expression patterns of negr1 and opcml at 24 hpf and 48 hpf. Dorsal (A,B,E,F) and lateral (C,D,G,H) views of the head region of zebrafish embryos at stages indicated. Insets show the pineal gland (A,B), the otic vesicle (C,D), the spinal cord (upper inset in C), and a frontal view (E). HB, hindbrain; OB, olfactory bulb; OP, olfactory placode; OV, otic vesicle; PTh, pre-thalamus; P, pineal gland; SC, spinal cord; V, ventral telencephalon.

Expression patterns of negr1 and opcml at 96 hpf and 120 hpf. Dorsal (A,B,E,F) and lateral (C,D) views of zebrafish larvae focussed on the head at stages indicated. Transversal sections were carried out at the level of the pineal organ (G,H). Ce, cerebellum (inset in (A,B)); Hb, habenula; INL, inner nuclear layer; OB, olfactory bulb; Pa, pallium; P, pineal gland; OT, optic tectum.