A complex population of RNAs exists in human ejaculate spermatozoa: implications for understanding molecular aspects of spermiogenesis

The presence of mRNAs in human ejaculate spermatozoa is well established, y et little is known of the representation or function of these transcripts. To address these issues, the complexity of spermatozoal RNA. was examined. As expected, testis-expressed mRNAs were detected by RT-PCR in mature human spermatozoa. Interestingly, when a testis cDNA library was probed with tot al spermatozoal RNA, less than 2% of plaques gave a strong hybridization si gnal, suggesting a rather unique sperm-derived population. To further defin e the sequence distribution, 18 strongly hybridizing clones were selected a t random for end-sequence analysis. Twelve matched unique sequences in the EST, STS and NR databases, whereas five showed no similarity to any of the sequences in the databases. In addition, one clone belonged to the SINE rep etitive element family. As demonstrated by sequencing randomly primed clone d inserts, short (SINE/MER) or long (LINE/ORF2) interspersed repeat-like se quences are also contained as part of the spermatozoal RNA fraction. It is now evident that human spermatozoa contain a rich repertoire of both known and unknown protein-encoding and non-coding RNAs. This provides a unique op portunity to identify and investigate the many genes responsible for the st ructure and function/dysfunction of the male gamete using spermatozoal RNA as the template. (C) 1999 Elsevier Science B.V. All rights reserved.