Nuclear transplantation and the control of gene activity in animal development

Abstract

The transplantation of nuclei from differentiated or determined somatic cells to enucleated frogs’ eggs consistently leads to a complete and clearly recognizable change of gene activity. Within 1 to 2 h of nuclear transfer, somatic nuclei have come to resemble in structure and metabolism the zygote nuclei of fertilized eggs. The change in gene activity therefore takes place very soon after nuclear transfer and results from an effect of egg cytoplasm. The induced change in gene activity is associated with a selective accumulation of cytoplasmic proteins in transplanted nuclei. Examples are given of various ways in which nuclear transplantation and microinjection can be used to elucidate the intracellular movement of proteins and the effect of known protein fractions on gene activity.