Possible synapse formation by embryonic cerebellar tissue grafted into the cerebellum of the weaver mutant mouse

The weaver mutant mouse is characterized by degeneration of cerebellar granule cells in early post-natal stage. In the present study, the possibility of synapse formation in the weaver mouse cerebellum by implanted granule cells was analyzed immunohistochemically with antiserum against synaptic vesicle protein, Synapsin I. Normal cerebellar tissue, obtained from 15-day-old CBA/JNCij mouse embryos, was transplanted into the cerebellum of 4-week-old weaver mice. 6 weeks after the transplantation, the grafted tissue was clearly detected in the host cerebellum, developing a trilaminar organization. A number of granule-like cells were observed in the folia of the host cerebellum, suggesting that the implanted granule cells may have migrated from the grafted tissue into the host cerebellum. Some areas in the host cerebellum as well as in the grafted tissue were intensely stained by anti-Synapsin I serum, indicating that the implanted granule cells make synaptic contacts with the neuronal cells.