[Nuclear transfer and cell differentiation: contribution of cloning to the study of embryonal stem cells].

The birth of physiologically normal and fertile animal of several mammalian species following the transfer of somatic nuclei into recipient enucleated oocytes has stimulated researches on the functional plasticity of cells available from living organisms. This experimental approach, termed cloning, has up to a low efficiency. It however allows the study of mechanisms compatible with the reacquisition of an undifferentiated nuclear status and contributes to researches aimed at controlling the fate of stem cells for therapeutically applications.