Characterization and quantification of mRNA transcripts in ejaculated spermatozoa of fertile men by serial analysis of gene expression

BACKGROUND: Accumulated evidence proves that mature spermatozoa contain a complex yet specific array of mRNA, which could provide information on the past events of spermatogenesis. OBJECTIVE: To quantitatively microdissect these mRNA transcripts by a digital approach. METHODS: Serial analysis of gene expression (SAGE) was used to study the mRNA transcripts from ejaculate of a fertile individual and of a pool of 10 fertile men. Online DAVID software suite was also utilized to cluster the UniGene data. RESULTS: A SAGE library from the individual produced 20 237 raw tags representing 2459 unique tags and that from pooled 10 men generated 21 052 raw tags representing 2712 unique tags. When the unique tags occurring ≥4 times were analysed, 564 overlapping tags were produced by 638 unique tags from the individual and 682 from the pooled library. Fifty-four of these overlapped tags were considered to be novel genes. Online analysis of the overlapping tags revealed 25 functional gene groups, with the dominant one comprising 96 nuclear protein genes involving transcription and transcription regulation and also a group with 84 ribosomal subunit genes involving protein synthesis. CONCLUSION: A SAGE analysis of ejaculate from fertile men has revealed a large number of transcripts, which occur in steady frequencies and probably have important roles in spermatogenesis and fertilization.