The structure and role of mammalian sperm RNA: a review.

The main role of sperm is the delivery of the paternal genome into the oocyte during fertilisation. However, several lines of evidence have indicated that mammalian spermatozoa contribute more than just their DNA, namely, they also deliver a large range of RNA molecules. Microarray analysis has revealed a complex population of 3000 different kinds of messenger RNA that are delivered to oocytes by sperm and ejaculated spermatozoa are estimated to contain about 0.015 pg of total RNA. Some of the transcripts encode proteins crucial for early embryo development. Messenger RNAs from sperm also help to protect the paternal genes, which have an integral role soon after fertilisation. The molecular participation of the oocyte during fertilisation is well understood but the function of the sperm in this process remains unclear. During spermatogenesis the structure of the male haploid genome is permanently modified. Transition proteins (TNPs), protamines (PRMs) and histones (HILS-spermatid specific linker histone) play a unique role in spermatid chromatin compaction. In this review, the structure and role of sperm RNA as well as chromatin organisation during spermatogenesis are discussed.