Differential gene expression analysis of eys+/-; lrp5+/- zebrafish eye by microarray

Vision is essential for vertebrates including humans. Sustained vision is accomplished by retinoid metabolism, the ‘visual cycle’, where all-trans retinol (atROL) is incorporated into the retinal pigment epithelium (RPE) from photoreceptors presumably through decade-long missing receptor(s). Here, we show that the LDL-related receptor-5 (Lrp5) protein is linked to the retinol binding protein 1a (Rbp1a), the transporter of atROL in the visual cycle, by generating and analyzing the digenic eyes shut homolog+/-; lrp5+/- zebrafish, the same form of gene defect detected in a human case of inherited retinal degeneration. Global gene expression analysis followed by genetic study clarified that rbp1a played a role downstream of lrp5. Rbp1a protein was colocalized with Lrp5 protein at microvilli of RPE cells. Furthermore, Rbp1a directly bound to the C-terminal intracellular region of Lrp5 in vitro. Collectively, these results strongly suggest that Lrp5 is a potent candidate of the receptor of atROL in the visual cycle. Grobal gene expression was compared between eys+/-; lrp5+/-, eys-/- or lrp5-/- eyes and wildtype eyes at 3.5 months post-fertilisation (3.5 mpf) zebrafish using Affymetrix microarray