page 733 that bonemarrow-derived stem cells can differentiate into apparently normal Purkinje neurons in an adult mouse brain. Although previous work demonstrated that bone marrow transferred into an irradiated mouse could give rise to cells expressing neuronal markers, the authors are the first to identify donor-derived neurons that appear to be morphologically normal and functional, and to determine that the donor-derived cells survive as the mouse ages.
The authors transferred the green fluorescent protein (GFP) gene into donor bone marrow cells, and then identified GFP- expressing cells in the brains of mice that received the transplanted bone marrow. Donor-derived Purkinje cells were not seen four months after transplantation, but had appeared by 12 months posttransplantation and persisted at least three months beyond that, observations that encompassed most of the lifespan of the mice. Priller et al. speculate that the delayed colonization of the cerebellum by the donor cells may be due to the death of the recipient's original Purkinje cells during aging. If true, this model suggests that bone marrow-derived stem cells might be able to preferentially regenerate neurons lost to aging or disease. ▪