โ Scribed by Houdebine, Louis-Marie
No coin nor oath required. For personal study only.
Present progress makes it possible to make some predictions for the use of animal transgenesis and cloning. Others are obviously impossible in a field where things are moving so rapidly.
Cloning techniques are expected to improve significantly. This is exemplified by the recent success with rabbit cloning (Chesne ร et al., 2002). Subtle modifications in the protocol respecting rabbit specificity led to this success. Rabbits are characterized by the rapid kinetics of their embryo cell cycle and by a narrow window of time for embryo implantation. The modifications taking these specificities into account are not expected to be extrapolated, as such, to other species but they do invite researchers to address cloning differently in order to increase their chances of success. The possibility of cloning rabbits opens new avenues to study differentiation and dedifferentiation but also to create relevant animal models to study human diseases.
Cloning techniques should reach a level of reliability and efficiency compatible with the reproduction of farm animals and pets. The possible extension to humans, independently of ethical considerations, is unpredictable.
To avoid the use of human oocytes for cloning, the possibility of using cow oocytes has been envisaged. It is by no means certain that the compatibility between the two species would be sufficient to allow the normal development of embryos. One of the problems would be the presence of cow mitochondria transmitted by the oocytes. The replacement of cow mitochondria by human mitochondria might be a possible approach (Mollard, Denham and Thomson, 2002). The use of cow oocytes might be compatible with therapeutic cloning, which implies only stem cell differentiation and not embryo development.
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