Ataxic Syrian Hamster

Abstract

A spontaneous genetic model of cerebellar ataxia in the Syrian hamster (Mesocricetus auratus) is described. Breeding data indicate that the ataxic condition is inherited as an autosomal recessive trait. The homozygous mutant hamsters are smaller in size than the unaffected littermates but have a normal appearance. Both homozygous males and females are fertile, and females are able to nurture litters. They develop a progressive but moderate ataxia beginning at 7 weeks of age; however, they live a normal life span. The major pathologic change in the ataxic mutants is significant cerebellar atrophy, including a rapid and substantial loss of Purkinje cells. Despite the obvious corticocerebellar atrophy, the general structure of the cerebellum is well retained. In addition, most other regions in the brain appear normal by light microscopy. The degeneration of cerebellar Purkinje cells starts after the third postnatal week in mutants and peaks around the fifth week; they then lose almost all Purkinje cells by around 18 months old. They also exhibit a slow and moderate reduction in granule-cell density, probably as a consequence of the primary loss of Purkinje cells. In the homozygous hamster brain, expression of Nna1, the gene responsible for the Purkinje cell degeneration (pcd) phenotype in mice, is suppressed. A phenotypic comparison of the ataxic hamsters with the pcd mutant mice suggests that influence of the causal allele in ataxic hamsters is considerably milder than those of most of the alleles found in the pcd mice. Thus, this ataxic Syrian hamster is a unique animal model of cerebellar ataxia with a severity distinct from any of the pcd phenotypes in mice.