Aberrant tectal patterning is observed in pbx2/4 null embryos. efna2 expression includes the posterior forebrain, the tectum, and the anterior hindbrain in wild type embryos (A), and is reduced in pbx2/4 null embryos (B) at 24 hpf. The expression of both nat10 and fabp7a includes both the eye and tectum in wild type embryos (C) and (E), and is almost completely absent in both regions in pbx2/4 null embryos (D and F). otx2 is expressed in the optic tectum at 48 hpf, specifically toward the periphery of the tectum with lower levels observed immediately adjacent to the eye (G). In pbx2/4 null embryos, there is a distinct change in expression domain in which the highest levels of expression are observed immediately adjacent to the eye (H). The gradient of efnA5a expression, which decreases toward the anterior (I), is attenuated at 48 hpf in pbx2/4 null embryos (J). The acetylated tubulin antibody marks the axons of the optic tectum at 3 dpf (K), which is smaller and disorganized in pbx2/4 null embryos (L).