PAX6 and microphthalmia: However, Kim and Lauderdale showed that Pax6ΔPD has a distinct function in mammalian eye development than Pax6 and Pax6(5a), since the overexpression of Pax6ΔPD, while using BAC and YAC transgene systems, lead to severe microphthalmia in both wildtype and Pax6-deficient mice [36,37].