Sperm/DNA interaction: integration of foreign DNA sequences in the mouse sperm genome

Foreign DNA is spontaneously taken up by mouse epididymal sperm cells and is further internalized into nuclei. The interaction and/or internalization of the exogenous DNA triggers the activation of sperm endogenous nucleases which mediate rearrangements of the internalized DNA. Foreign DNA sequences are found to be tightly bound to the sperm nuclear scaffold, and to undergo a recombination process with the sperm chromosomal DNA. Sequence analysis of randomly selected clones from a library of sperm genomic DNA transformed with pSV2CAT plasmid showed that foreign sequences were integrated in a unique site of the sperm genome. Preliminary results suggest that the integration process is mediated by a retrotranscription step.