Nucleostemin protein is found in the nucleoli of CNS stem cells, embryonic stem cells, and several cancer cell lines, and partly controls stem and cancer cell proliferation. It is not found in the differentiated cells of most adult tissues. Rabbit anti-human, rabbit anti-mouse, and chicken anti-human nucleostemin antibodies are now available, used successfully for Western blotting and in the identification of embryonic and adult CNS stem cells in culture.