Microarray screening allows the investigator to profile expression patterns on a genome-wide scale. However, even a successful screen can generate a daunting amount of data. In our effort to identify genes involved in sperm development, we compared expression levels in
fem-3(gf) mutants, which make only sperm, to
fem-1(lf) mutants, which make only oocytes. We identified 650 sperm-enriched genes (as well as 258 oocyte-enriched genes) out of 11,917 genes screened (see Reinke et al.). Now, how do we use this information? We have focused our efforts in two areas: 1) obtaining deletion mutations in potentially interesting genes; and 2) identifying sperm promoter elements and their relevant transcription factors. Prior work with the calmodulin inhibitor trifluoperazine (TFP) had implicated Ca++ function in both sperm activation and motility; therefore, we generated a deletion allele of the sperm-enriched Ca++ channel gene K01A11.4 (since named
spe-39). The
spe-39 mutant exhibits reduced fertility and an aberrant sperm morphology that mimics TFP treatment. We can now examine the role of other spe mutants in Ca++ sensing, sperm activation, and motility. We are using an in silico approach to identify potential sperm promoter elements, and molecular and genetic analyses to confirm functional significance. The algorithm (written by John Anderson, NCBI) determines which sequences are over-represented in the 5' upstream sequences of sperm genes compared to non-sperm genes. One of these sperm-enriched sequences contains two potential binding sites for the GATA transcription factor
elt-1. Prior work has shown that
elt-1 is required to specify hypodermal cell fates in the developing embryo; however, our microarray data also identified
elt-1 as a sperm-enriched gene. Yeast one-hybrid screening demonstrates that
elt-1 binds to and activates transcription from these putative promoter elements. In collaboration with Barbara Page, we are currently investigating the role of
elt-1 in sperm development.