spe-10 encodes a DHHC-CRD zinc-finger membrane protein required for endoplasmic reticulum/Golgi membrane morphogenesis during Caenorhabditis elegans spermatogenesis

C. elegans spermatogenesis employs lysosome-related fibrous body-membranous organelles (FB-MOs) for transport of many cellular components. Previous work showed that spe-10 mutants contain FB-MOs that prematurely disassemble, resulting in defective transport of FB components into developing spermatids. Consequently, spe-10 spermatids are smaller than wild type and contain defective FB-MO derivatives. In this article, we show that spe-10 encodes a four-pass integral membrane protein that has a DHHC-CRD zinc-finger motif. The DHHC-CRD motif is found in a large, diverse family of proteins that have been implicated in palmitoyl transfer during protein lipidation. Seven spe-10 mutants were analyzed, including missense, nonsense, and deletion mutants. An antiserum to SPE-10 showed significant colocalization with a known marker for the FB-MOs during wild-type spermatogenesis. In contrast, the spe-10(ok1149) deletion mutant lacked detectable SPE-10 staining; this mutant lacks a spe-10 promoter and most coding sequence. The spe-10(eb64) missense mutation, which changes a conserved residue within the DHHC-CRD domain in all homologues, behaves as a null mutant. These results suggest that wild-type SPE-10 is required for the MO to properly deliver the FB to the C. elegans spermatid and the DHHC-CRD domain is essential for this function.