Identification of human sperm transcripts as candidate markers of male fertility.

To date, there has been little progress towards identifying markers of normal male fertility. The need to supplement current subjective methods that rely on variable semen parameters to assess fertility status continues to be acknowledged. Several studies have shown that spermatozoal RNAs can describe characteristic failures of the spermatogenic pathway among infertile males. In spite of the inherent heterogeneity of semen that describe the "normal" fertile male, this holds the promise of developing markers that could help identify the ever elusive idiopathic infertile male. Through the analyses of the spermatozoal transcriptome from 24 donors of proven fertility, we identified a series of transcripts that were consistently present among all individuals. The heterogeneous nature of the samples, reflected by their semen parameters, was mirrored by the variability of the observed array signal. Nevertheless, clusters of invariable transcript pairs were identified. These were founded by a single central member that was linked in constant proportion even though the absolute level of each member of the transcript pair often varied among individuals. The presence of pairs of stable transcripts suggests that among the heterogeneity observed in the sperm transcriptome, a distinct set is strictly regulated.