Using somatic-cell nuclear transfer to study aging.

In mammals, a diploid genome following fertilization of haploid cells, an egg, and a spermatozoon is unique and irreproducible. This implies that the generated unique diploid genome is doomed with the individual's inevitable demise. Since it was first reported in 1997 that Dolly the sheep had been cloned, many mammalian species have been cloned successfully using somatic-cell nuclear transfer (SCNT). The success of SCNT in mammals enables us not only to reproduce offspring without germ cells, that is, to "passage" a unique diploid genome, but also to address valuable biological questions on development, nuclear reprogramming, and epigenetic memory. Successful cloning can also support epigenetic reprogramming where the aging clock is reset or reversed. Recent work using iPS cell technology has explored the practicality and led to the recapitulation of premature aging with iPSCs from progeroid laminopathies. As a result, reprogramming tools are also expected to contribute to studying biological age. However, the efficiency of animal cloning is still low in most cases and the mechanism of reprogramming in cloned embryos is still largely unclear. Here, based on recent advances, we describe an improved, more efficient mouse cloning protocol using histone deacetylase inhibitors (HDACis) and latrunculin A, which increases the success rates of producing cloned mice or establishing ES cells fivefold. This improved method of cloning will provide a strong tool to address many issues including biological aging more easily and with lower cost.