Since 1997, when Dolly the sheep was born, many animal species have been cloned by somatic cell nuclear transfer (SCNT). However, although a source of genetically identical non-human primates for biomedical research would be invaluable, SCNT has yielded no viable primates so far. On , Ng et al. investigate the first cell cycle after SCNT in Long-tailed Macaques(Macaca fascicularis). They show that a spindle of unduplicated premature condensed chromosome (PCC spindle) can form from donor cells injected into enucleated M. fascicularis oocytes. Furthermore, after oocyte activation, cell division can occur and reconstituted embryos can establish pregnancies, although these fail to progress to term. These data challenge the recent controversial proposal that SCNT failure in primates results from the loss during egg enucleation of the molecular signals necessary for spindle formation, but support the idea that incomplete nuclear reprogramming underlies SCNT failure.
