RNA in spermatozoa: implications for the alternative haploid genome

The presence of specific messenger RNAs in the nuclei of mature mammalian spermatozoa has been demonstrated by several independent laboratories. Others have suggested that various polymerases may also be active in mature spermatozoa. This has led to the notion that the 'sleeping' genome may not be so quiescent after all. The alternate use of somatic-like nucleosomal and haploid protamine packaging structures to assemble sperm chromatin and the ordered array of chromosomes within the mature human sperm nucleus support this view. This had led us to address the issue of whether a somatic-like organization of select regions of the paternal genome and the mRNAs present in spermatozoa were correlated. Results from this and other laboratories suggest that this in indeed the case. Potential roles for this novel packaging and the accumulation of transcripts within the mature human nucleus are discussed.