Fig. 1

Fig. 1

Engrailed gain of function results in reduction in both pax6 expression domain and eye size. (A-F) mRNA encoding En2ER^T2 was injected at the one-cell stage and the protein was activated at different times of development. Eye size reduction (up to total disappearance) and axis abnormality phenotypes (A) were scored at different times of activation controlled by cyclofen release (B). WT, wild type; epi, epiboly. Diencephalons were measured on flat-mount embryos as the anterior pax6 expression domain (C) and compared to the eye phenotype (mean of the two eye sizes) for each embryo (D), demonstrating the correlation between these two parameters. White asterisks, eye position; red squares, control; blue squares, activated Engrailed. The dashed red line indicates the limit below which eyes were scored as reduced (or absent). All the embryos of this class (yellow box) have a small anterior pax6 expression domain. Additional effects of En2 activation were apparent at the 2-3 somite stage with the loss of the anterior pax6 expression domain (E) and at 4dpf with the selective loss of the pretectal vmat2:GFP neuronal cluster (red asterisk) (F). Pr, pretectal cluster; Ra, raphe.