Allocation of distinct organ fates from a precursor field requires a shift in expression and function of gene regulatory networks.

A common occurrence in metazoan development is the rise of multiple tissues/organs from a single uniform precursor field. One example is the anterior forebrain of vertebrates, which produces the eyes, hypothalamus, diencephalon, and telencephalon. Another instance is the Drosophila wing disc, which generates the adult wing blade, the hinge, and the thorax.

Pax6 promotes development of the entire eye-antennal disc, thereby ensuring proper adult head formation.

Paired box 6 (Pax6) is considered to be the master control gene for eye development in all seeing animals studied so far. In vertebrates, it is required not only for lens/retina formation but also for the development of the CNS, olfactory system, and pancreas. Although Pax6 plays important roles in cell differentiation, proliferation, and patterning during the development of these systems, the underlying mechanism remains poorly understood.