Reverse transcriptase activity in mature spermatozoa of mouse

We show here that a reverse transcriptase (RT) activity is present in murin e epididymal spermatozoa, Sperm cells incubated with human poliovirus RNA c an take up exogenous RNA molecules and internalize them in nuclei. Direct P CR amplification of DNA extracted from RNA-incubated spermatozoa indicate t hat poliovirus RNA is reverse-transcribed in cDNA fragments. PCR analysis o f two-cell embryos shows that poliovirus RNA-challenged spermatozoa transfe r retrotranscribed cDNA molecules into eggs during in vitro fertilization. Finally, RT molecules can be visualized on sperm nuclear scaffolds by immun ogold electron microscopy, These results, therefore, reveal a novel metabol ic function in spermatozoa, which may play a role during early embryonic de velopment.