Since there was an elevated fasting blood glucose level in adult Pcsk1n transgenic mice and impaired glucose tolerance in the Cpefat/fat background transgenic mice [21], we sought to investigate whether the Pcsk1n expression is altered in the Pax6 mutant mice, and if so, whether the alteration would affect PC1/3 C-terminal cleavage and activity, thereby contributing to the abnormal proinsulin processing and onset of diabetes in these Pax6 mutant mice. The gene discussed is PAX6; the disease is diabetes mellitus.