Though the spermatozoa of many animal species can take up DNA molecules and internalize them into nuclei, Giordano and colleagues (page 1107) present the first evidence that murine spermatozoa can take up and retrotranscribe RNA. Since the resulting cDNA molecules are subsequently transferred into eggs, the reverse transcriptase (RT) activity of mammalian spermatozoa could play a role in embryonic development.
In previous work, the same lab found that nuclease-hypersensitive DNA from murine spermatozoa contains a high proportion of sequences of retrotransposon origin. Reasoning that the RT activity expressed by these sequences might have persisted, the researchers incubated mouse spermatozoa with purified human poliovirus RNA, and then tested for the production of cDNA by PCR amplification. The poliovirus RNA is reverse transcribed by spermatozoa, and analysis of two-cell embryos produced by in vitro fertilization shows that RNA-incubated spermatozoa transfer the...
