Fig. 4

Photoreceptor transcripts in larval zebrafish show that nrl−/−; tbx2b−/− mutants recapitulate phenotypes of nrl−/− mutants. The nrl mutant zebrafish larvae have significantly increased levels of mRNA abundance compared to wildtype, consistent with the notion that nrl has auto-regulatory properties. Similarly, tbx2b mutants also have high nrl transcription, suggesting a repressive interaction. The nrl−/− and nrl−/−;tbx2b−/− mutants share consistently similar transcription profiles across most other assayed genes. Examination of the opsin genes expressed in rods (rho1) and UV cones (sws1) reveals disruption to expected levels of opsin relative to observed abundance of each cell type. Despite their observed overabundance of rods, tbx2b mutants have slightly lower levels of rho1 transcription. Similarly, despite nrl and nrl−/−/tbx2b−/− mutants having increased UV cone abundance, sws1 mRNA abundance does not show similar increases. Error bars represent standard error of the mean. N = 3 to 6 biological replicates. * = P < 0.05, ** = P < 0.005, *** = P < 0.0005 as determined by Brown-Forscythe and Welch 1-way ANOVA with Dunnett T3’s multiple comparison tests.