NR0B1 and chronic primary adrenal insufficiency: Another successful gene deletion was shown by Kang et al. They successfully knocked out DAX1 (dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1) in cynomolgus monkeys, and the DAX1-deficient monkey displayed an adrenal gland development defect, abnormal testis architecture and unaffected Sertoli cell formation.