Hereditary Progressive Ankylosis, Mouse

Abstract

Progressive ankylosis, ank, an autosomal recessive mutation in laboratory mice, causes a debilitating joint disorder (Sweet and Green 1981). A difference in body weight between affected and nonaffected littermate pups may be detected as early as 10 days of age. The first observable clinical sign, rigidly extended toes on the forefeet, occurs when the homozygous animal is 4-5 weeks of age. The toes on the hind feet become rigid approximately 7 days after the forefeet are affected. Locomotion is accomplished by a slow halting gait with all feet flat against the surface, or by pivoting the ankle, toes held slightly above the surface. By 3 months of age, the homozygote has become increasingly immobile. Adults have a rigid posture, frequently remaining in a crouched position, with thoracic kyphosis and prominent haunches. No gross lesions other than those of bones and joints have been observed in ank/ank mutants 7 weeks to 8 months of age. Most of the affected animals are euthanatized by anoxia with CO2 between 4 and 6 moths of age because of the inability to reach food and water. Abnormal and excessive calcification of the joints can be seen in alizarin-stained cleared skeletons (Figs. 334, 335).