Expression of interphotoreceptor retinoid-binding protein (IRBP) and opsin during zebrafish development

Interphotoreceptor Retinoid-Binding Protein (IRBP) facilitates the transport of vitamin A during the visual cycle and may play a role in development. We propose to study the possible role of IRBP during zebrafish retinal development. Purpose: To determine the timecourse of onset and upregulation of gene expression of IRBP relative to that of opsin during zebrafish development. Methods: Relative levels of IRBP and opsin were measured by RT-PCR co-amplification of both mRNA's from zebrafish embryos at different developmental timepoints. In situ hybridizations were performed using a full-length digoxygenin-labelled probe for zebrafish IRBP. Results: Results indicate that both IRBP and opsin are expressed early during zebrafish development. Expression of IRBP mRNA appears to be upregulated to adult levels earlier than expression of opsin mRNA. IRBP mRNA is present prior to retinal photoreceptor differentiation. In situ hybridization localizes IRBP mRNA to cones. Conclusions: Expression of IRBP mRNA is upregulated prior to upregulation of expression of opsin mRNA during zebrafish development.