Uptake of Heterologous Genome by Mammalian Spermatozoa and Its Transfer to Ova through Fertilization

Abstract

Simian virus 40 (SV40) adsorbs on rabbit spermatozoa but does not penetrate the cells, as indicated by the absence of radioactive material seen on autoradiography of spermatozoa exposed to [(3)H]thymidine-labeled SV40. In contrast, after exposure of spermatozoa to labeled SV40 DNA, radioactive material was found in the postacrosomal area of the spermatozoa. Furthermore, when spermatozoa exposed to SV40 DNA were fused with cells of the CV-1 line of African green monkey kidney cells, infectious SV40 was isolated. After uterine insemination of rabbits with spermatozoa infected with SV40 DNA, both unfertilized and one- and two-celled fertilized ova were obtained. When the fertilized ova were cocultivated with CV-1 cells, infectious virus was recovered. In contrast, CV-1 cells exposed to the unfertilized ova or to zonae pellucidae or polar bodies from the fertilized ova did not show a cytopathic effect. This report provides the first evidence that a heterologous genome can be incorporated into a mammalian spermatozoon and subsequently carried into an ovum during the process of fertilization.