[Molecular biological analysis of the development of the mammalian central nervous system]

Analysis of the neuropathological mutant animals offers us great information on the development and differentiation of the nervous system. I have here introduced two examples of the analyses of the various kinds of neuropathological mutant mice. First one is the mutant mice where Purkinje neurons in the cerebellum are absent. High molecular weight protein, P400, enriched in the Purikinje cells in the cerebellum was greatly decreased in the Purkinje cell deficient mutant mice, nervous, pcd, Lurcher. We demonstrated that P400 is equivalent to IP3 receptor type 1. We found that IP3 receptor type 1 plays an important role in Ca2+ wave in fertilization and long term depression in the cerebellum which is one of the typical example of neuronal plasticity in the cerebellum. Second mutant is reeler mice where neuronal positioning in the brain is abnormal. We found CR50 antigen, reelin is the key molecule as a secreted molecule from Cajal-Retzius neuron for the neuronal positioning. We produced IP3 receptor deficient mice by gene targeting. The birth rate was one fifth of the control and the animals die before 25 postnatal days. They showed cerebellar ataxia and epileptic seizure.