Nuclear Transfer from Cell Lines

Abstract

The production of cloned animals following nuclear transfer, using somatic cells grown in culture, represents a remarkable feat of developmental biology. It demonstrates the potential of a differentiated nucleus to be reprogrammed back to an embryonic state when exposed to a suitable cytoplasmic environment, such as that of an enucleated oocyte. It involves fundamental changes to the patterns of DNA methylation and chromatin modification imposed on a specialised nucleus to enable the precise temporal‐spatial sequence of gene expression necessary for normal embryogenesis. However, reprogramming is often incomplete with development going astray, resulting in a continuum of embryo, fetal and postnatal mortality. The majority of the clones that do survive to adulthood, and their sexually derived progeny, do, however, appear normal. This provides encouragement for the practical applications of nuclear cloning in the fields of agriculture, animal conservation and biomedicine. Key Concepts The cytoplasm of mature oocytes has the potential to reprogramme the epigenetic state and pattern of gene expression of differentiated donor cells back to that of an embryo following nuclear transfer, enabling the production of cloned animals. The success rate of cloned animals is more influenced by differences in nuclear transfer method than by the type of animal or cell. Because cultured cells can be multiplied, cryopreserved, andused at any time, cloning animals from cultured cells has many advantages overusing fresh cells collected from animals. Using nuclear transfer technology, embryonic stem (ES) cell lines can be generated from somatic cells, and cloned animals can be produced using these cultured cells as donors. Epigenetic abnormalities frequently occur in cloned animals, but the next generation born from the cloned parents are normal and can be used without problems in livestock production. Cloning technology could help save endangered species.