Fig. 9. The cis-regulatory elements of mouse LATE and LSE direct GFP expression in the zebrafish diencephalon and the telencephalon, respectively. The left panels show a cumulative map of the expression (blue dots; n, number of embryos analysed) of the reporter and the right panels are representative images of embryos injected with the construct indicated in the right bottom corner. Reporter gene expression was revealed by hybridising embryos to the antisense gfp probe. Blue and red boxes in the schematic drawings indicate zebrafish and mouse enhancers, respectively. (A-C) Embryos injected with –3.1ngn1:gfp, with mutant derivatives without the zebrafish LATE [–3.1ngn1(delLATE):gfp], or with a replacement with the mouse LATE [–3.1ngn1(msLATE):gfp]. Mouse LATE drives expression in the zebrafish diencephalon in a pattern very similar to zebrafish LATE. Like its zebrafish homologue, mouse LATE does not mediate expression in the zebrafish telencephalon (indicated by arrows). (D-F) Embryos were injected with the –8.4ngn1:gfp transgenes, with mutants without the LSE [–8.4ngn1(delLSE):gfp], or with the mouse LSE in place of the homologous zebrafish sequence [–8.4ngn1(msLSE):gfp]. As shown in stable expression experiments, the absence of the LSE significantly reduced the expression of the reporter in the telencephalon. The replacement of the zebrafish LSE with the homologous mouse LSE restored reporter expression in the telencephalon.