The Pax4/6 genes, also known as Pax group IV, encodes proteins with a PRD domain and a complete PRD-type homeodomain. There are two genes in human, one in amphioxus and two clear examples in Drosophila (ey, toe). There are two additional related genes in Drosophila with a partial Pax domain which may be part of this gene family (eyg, toy); these are included here.
There is some confusion as to whether the Pax4/6 gene family this should be split into two gene families (Pax4 and Pax6), because invertebrate homologues generally group with PAX6 in phylogenetic analyses and not as an outgroup. However, this could be explained by extreme divergence of PAX4 causing violation of assumptions made in phylogenetic analysis.