KK mice are produced and maintained in the same manner as that used for normal inbred mice. Because female KK-Ay mice are sterile, male KK-Ay mice are mated with female KK mice for breeding. Because C57BL/6-Ay is used when the Ay gene is introduced, the above breeding causes albino, black, and yellow animals. Among these, yellow-haired animals are selected as KK-Ay mice.
BKS.Cg-m +/+ Leprdb/Jcl
Male homozygotes have spermatogenic defects and female homozygotes have gonadotropic hormone secretion disorder, probably because of a hypothalamic disorder (Johnson et al., 1979). Thus, both males and females of this strain are sterile. Mice of this strain are produced by mating female and male heterozygotes (m +/+ Leprdb) that have the marker misty (pale hair color) crosslinked on the Leprdb gene locus on the fourth chromosome. Through this breeding, misty (m +/m +), hetero (m +/+ Leprdb), and homo (+ Leprdb/+Leprdb) litters are born at a ratio of about 1:2:1. Because misty mice have gray hair and hetero and homo mice have black hair, black mice are selected for observation at 5 weeks of age. At that time, obese animals are regarded as homo and non-obese animals are regarded as hetero; 6-week-old or older mice are supplied to customers. Mice in the rearing place are given autoclaved CE-2 (121° 30 min) and chlorine-containing (4 - 6 ppm) water ad libitum.