Remodeling somatic nuclei via exogenous expression of protamine 1 to create spermatid-like structures for somatic nuclear transfer

This protocol describes how to convert the chromatin structure of sheep and mouse somatic cells into spermatid-like nuclei through the heterologous expression of the protamine 1 gene (Prm1). Furthermore, we also provide step-by-step instructions for somatic cell nuclear transfer (SCNT) of Prm1-remodeled somatic nuclei in sheep oocytes. There is evidence that changing the organization of a somatic cell nucleus with that which mirrors the spermatozoon nucleus leads to better nuclear reprogramming. The protocol may have further potential application in determining the protamine and histone footprints of the whole genome; obtaining 'gametes' from somatic cells; and furthering understanding of the molecular mechanisms regulating the maintenance of DNA methylation in imprinted control regions during male gametogenesis. The protocol is straightforward, and it requires 4 weeks from the establishment of the cell lines to their transfection and the production of cloned blastocysts. It is necessary for researchers to have experience in cell biology and embryology, with basic skills in molecular biology, to carry out the protocol.