This was confirmed in these PAX4 KO rabbits, due to complete damage of PAX4 gene structure and function caused by large fragment deletions, destroyed, incomplete pancreatic islet structure, decreased numbers of insulin-producing β cells and increased numbers of glucagon-producing α cells were observed in the KO rabbits, leading to persistent hyperglycemia and lethality of the PAX4−/− rabbits. The gene discussed is GCG; the disease is Hyperglycemia.