Reconstitution of sperm nuclei of zebrafish (Danio rerio) in Xenopus egg extracts

Cell-free extracts of Xenopus eggs cause cyclic change in permeabilized spe rm nucleus, nuclear envelope breakdown, chromosome condensation, and reform ation of nuclei. In this study, the ability of cell-free extracts to cause similar changes in zebrafish sperm was examined. When lysolecithin-treated sperm from zebrafish were incubated in Xenopus egg extracts, a series of ch anges in sperm nuclear morphology were observed periodically. These changes correlated with maturation-promoting factor (MPF) activity. Furthermore, s perm nuclei of zebrafish replicated DNA during reconstitution in Xenopus eg g extracts. These results showed that cell-free extracts of Xenopus egg pos sess the ability to cause cell-cycle-dependent changes in zebrafish sperm, implying the possibility of generating transgenic zebrafish in a similar wa y to transgenic Xenopus.