Gender effect on Purkinje cell loss in the cerebellum of the heterozygous reeler mouse

Homozygous mutant mice such as staggerer (sg/sg) or reeler (rl/rl) exhibit a marked ataxia associated with an atrophic cerebellum during the first postnatal weeks and a reduced number of Purkinje cells, the deficit reaching about 75% in sg/sg and 50% in rl/rl as compared to age and sex- matched mice from the same strain background. These two mutations are classically viewed as recessive, but we have recently shown that heterozygous staggerer (+/sg) mice exhibit a progressive and age-related loss of Purkinje cells between 3 and 12 months of age, despite their apparent clinical normality (Shojaeian-Zanjani et al., 1992). In the present study, we have investigated whether a similar cell loss exists in the cerebellum of heterozygous +/rl mice. The number of Purkinje cells was counted in serial parasagittal sections of the cerebellum of +/rl and their +/+ littermates at 3, 16 and 26 months of age. Our results reveal a 16% deficit in the number of Purkinje cells in 3-month-old +/rl and a 24% one in 16-month-old animals: surprisingly this deficit is only present in the +/rl males, while the females are spared. These results suggest that the reeler gene (D'Arcangelo et al., 1995) exerts its effect on Purkinje cell number in a gender-specific Fashion in heterozygous mutant mice.