Sir

According to Robert Triendl's News report (Nature 404, 321; 2000), reimplantation of human clones will probably continue to be prohibited in Japan, whereas experimentation into establishing human embryonic stem (ES) cells may be allowed.

On 17 December 1999, the cloning subcommittee (chaired by Yoshio Okada) of the Council for Science and Technology's bioethics panel concluded that human cloning should be restricted by law. A law being drafted this year will primarily cover the prohibition of nuclear transplantation of human somatic cells. However, on 6 March, the same subcommittee indicated that research to establish human ES cells should be allowed, subject to guidelines being developed.

As a consequence, there is increasing expectation of immediate progress in research into establishing human ES cells. In some universities, study protocols for related experiments have already been submitted to the appropriate ethics committees.

However, progress in experimentation using human embryos cannot be guaranteed unless some significant problems are resolved, including regulation of proprietary rights of intellectual possession and profits to be derived from the establishment of such cells; ownership by those involved in the experiment and/or the donor of fertilized eggs; and problems related to the donation of fertilized eggs.

Concerning the last problem in particular, donation of fertilized eggs to outside facilities, even with the donor's consent, may be against the guidelines of the Japanese Gynecology and Obstetrics Society. In any event, the society does not allow the use of fertilized eggs for anything other than infertility treatment.

If such problems are left unsolved, experiments to establish ES cells would be practically impossible even if the Council for Science and Technology does develop guidelines. Research using human ES cell strains from overseas may represent the most realistic option likely in Japan.