Fig. 2

Igf2bp1, the zebrafish ZBP1 ortholog, is expressed in RGCs during axon pathfinding.

(a) Phylogenetic tree generated with ClustalW, showing that of the four Igf2bp genes in Danio rerio Igf2bp1 is the most closely related to Gallus gallus Igf2bp1 of the four Igf2bp genes in Danio rerio, based on amino acid sequence. b) Schematic of zebrafish and chicken Igf2bp1 and β-actin mRNA, illustrating the conservation of protein domains and the presence of a bipartite nucleotide sequence in Danio rerio mRNA that is homologous to the zipcode sequence of chicken. These similarities at both the protein and mRNA levels suggest that in zebrafish, as has been shown in chicken, KH34 binds the putative zipcode sequence in the β-actin 3′UTR. (c) Schematic of mechanism for localization of β-actin mRNA by Igf2bp1 predicted to be conserved in zebrafish RGCs in vivo. (d) Wholemount in situ hybridizations performed on 22 hpf, 48 hpf, 34 hpf, and 72 hpf embryos show the location of Igf2bp1 mRNA expression. (e) 15 µm coronal plastic sections show Igf2bp1 mRNA expression in the RGC layer (white bracket in right panel), as well as the inner plexiform layer (yellow arrowhead), inner nuclear layer (green arrowhead), photoreceptor layer (red arrowhead) and RGC axons in the optic nerve (black arrowhead) in 3 dpf embryos. Scale bars are 100 µm (d) and 50 µm (e).