Genetic and molecular characterization of the Caenorhabditis elegans spermatogenesis-defective gene spe-17.

Two self-sterile mutations that define the spermatogenesis-defective gene spe-17 have been analyzed. These mutations affect unc-22 and fail to complement each other for both Unc-22 and spermatogenesis defects. Both of these mutations are deficiencies (hcDf1 and hDf13) that affect more than one transcription unit. Genomic DNA adjacent to and including the region deleted by the smaller deficiency (hcDf1) has been sequenced and four mRNAs (including unc-22) have been localized to this sequenced region. The three non unc-22 mRNAs are shown to be sex-specific: a 1.2-kb mRNA that can be detected in sperm-free hermaphrodites and 1.2- and 0.56-kb mRNAs found in males. hDf13 deletes at least 55 kb of chromosome IV, including all of unc-22, both male-specific mRNAs and at least part of the female-specific mRNA. hcDf1, which is approximately 15.6 kb, deletes only the 5' end of unc-22 and the gene that encodes the 0.56-kb male-specific mRNA. The common defect that apparently accounts for the defective sperm in hcDf1 and hDf13 homozygotes is deletion of the spe-17 gene, which encodes the 0.56-kb mRNA. Strains carrying two copies of either deletion are self-fertile when they are transgenic for any of four extrachromosomal array that include spe-17. We have sequenced two spe-17 cDNAs, and the deduced 142 amino acid protein sequence is highly charged and rich in serine and threonine, but shows no significant homology to any previously determined protein sequence.