ABSTRACT
INTRODUCTION Somatic cell nuclear transfer (SCNT) involves the transfer of somatic cell nuclei into enucleated oocytes. In almost all species, preimplantation development is successful after SCNT, giving blastocyst formation percentages almost comparable to in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) embryos (reviewed in Ref. 1). Concomitantly, the different steps in the SCNT process (e.g., cell cycle stage and type of recipient oocyte and donor cell, method used for nuclear transfer (NT) and artificial activation, culture environment) are well described and optimized in several animal models like the mouse, but not in human (for reviews see Refs. 1-4). Embryonic development after SCNT in nonhuman primates has been shown to be compromised (5-8), similarly as in human (reviewed in Ref. 9). Moreover, attempts at reproductive cloning in the nonhuman primate have resulted in little success, which has been attributed to removal of important microtubule proteins during enucleation of the recipient oocytes (6,7,10).
