[6] Pax-6 is expressed as a transcription factor when neural ectoderm receives a combination of weak Sonic hedgehog (SHH) and strong TGF-Beta signaling gradients.

This transcription factor is most noted for its use in the interspecifically induced expression of ectopic eyes and is of medical importance because heterozygous mutants produce a wide spectrum of ocular defects such as aniridia in humans.

An example of this lies in HD's regulatory involvement in the formation of the lens and retina throughout oculogenesis contrasted by the molecular mechanisms of control exhibited on the patterns of neurogenesis in brain development by PD.

The HD and PD domains act in close coordination, giving Pax6 its multifunctional nature in directing molecular signaling in formation of the CNS.

[15] Of the four Drosophila Pax6 orthologues, it is thought that the eyeless (ey) and twin of eyeless (toy) gene products share functional homology with the vertebrate canonical Pax6 isoform, while the eyegone (eyg) and twin of eyegone (toe) gene products share functional homology with the vertebrate Pax6(5a) isoform.

PAX6(5a) is a product of the alternatively spliced exon 5a resulting in a 14 residue insertion in the paired domain which alters the specificity of this DNA binding activity.

[7] During embryological development the PAX6 gene, found on chromosome 2 in mice, can be seen expressed in multiple early structures such as the spinal cord, hindbrain, forebrain and eyes.

PAX6 is essential is the formation of the retina, lens and cornea due to its role in early cell determination when forming precursors of these structures such as the optic vesicle and overlying surface ectoderm.

[20] PAX10 mutations also hinder nasal cavity development due to the similar precursor structures that in small eye mice do not express PAX10 mRNA.