Figure 5

Adult Retina of Zebrafish nrl^−/− Mutants Show Changes in Abundance of Nrl Target Gene nr2e3 and in nrl Itself

(A) Gene expression determined by in situ hybridization on cryosections of adult zebrafish retina. Abundance of nrl transcript is higher in nrl^−/− frameshift mutant retina (confirmed in panel B), suggesting an auto-regulatory negative feedback loop controlling it own abundance. Assuming that nrl transcript location is unaltered in nrl^−/− mutants (despite aforementioned changes in its abundance), these data suggest expression of nrl is highly enriched in the outer nuclear layer, consistent with the site of phenotypes when Nrl protein is disrupted. Alterations to the abundance of nr2e3, a downstream target of Nrl, are equivocal when measured by in situ hybridization. The levels and distributions of transcripts encoding rod (rh1) and cone (sws1 and rh2) opsins were not detectably different in nrl^−/− mutant retina compared to wild type. Scale bars represent 10 μm.

(B) Transcript abundance in adult neural retina determined by RT-qPCR confirms an increase in nrl abundance in zebrafish bearing a frameshift null allele in nrl. A downstream transcriptional target of Nrl, nr2e3, was 70% reduced in abundance in nrl^−/− mutant retina compared to wild type (p < 0.01; n = 5–6 individuals per genotype). Opsin abundances in adult retinas were not markedly different between genotypes.