Nuclear reprogramming: what has been done and potential avenues for improvements

Cloning the mammoth: a complicated task or just a dream?

Recently there has been growing interest in applying the most advanced embryological tools, particularly cloning, to bring extinct species back to life, with a particular focus on the woolly mammoth (Mammuthus primigenius). Mammoth's bodies found in the permafrost are relatively well preserved, with identifiable nuclei in their tissues. The purpose of this chapter is to review the literature published on the topic, and to present the strategies potentially suitable for a mammoth cloning project, with a frank assessment of their feasibility and the ethical issues involved.

Interspecies somatic cell nuclear transfer: a salvage tool seeking first aid

Much emphasis is currently given to the use of Interspecific Somatic Cell Nuclear Transfer (ISCNT) as a potential salvage tool for endangered animals. In this short review we present a survey on all data published so far on ISCNT, including abstract communication in international meetings. From the analysis of these data it appears that the results obtained are very preliminary and often confusing on the real stage of the embryonic development obtained. Moreover, the acronym ISCNT is improperly used because in many reports the nuclei and oocyte donor are not within the same species, but belong to different order and sometimes taxa, therefore, we classified all the ISCNT reports by allocating cell and oocyte donors to their respective order/species/class. The efficiency of cloning is low in all species owing to incomplete nuclear reprogramming of differentiated cells under the current procedures. ISCNT, however, poses additional hurdles which are rarely addressed in previously published work, and on which we focus in this review: mt/genomic DNA compatibility; embryonic genome activation of the donor nucleus by the recipient oocyte; availability of suitable foster mothers for ISCNT embryos. All these issues are discussed here, and possible solutions for the successful application of somatic cell nuclear transfer to endangered animals are also put forth.