Mature human spermatozoa do not transcribe novel RNA.

Mature spermatozoa contain subsets of mRNA that have been found in human testes before. Based on this finding it was hypothesized that the mRNAs of spermatozoa are transcribed during spermatogenesis. However, up to now there is no proof of the transcriptional inactivity of human sperm. To address this issue we performed in vitro labelling experiments with radio-labelled uridine triphosphate followed by analysis of cellular RNA. There was virtually no radioactive RNA detectable in the RNA purified from human spermatozoa proving the transcriptional inactivity of mature spermatozoa. The spermatozoal RNA obviously results from transcription during spermatogenesis and can be used for diagnostic purposes. These findings might have diagnostic and - possibly - therapeutic value in infertility patients as spermatozoal RNAs might complement the RNA pool of the oocyte after fertilization.