The presenilin protein family member SPE-4 localizes to an ER/Golgi derived organelle and is required for proper cytoplasmic partitioning during Caenorhabditis elegans spermatogenesis

During Caenorhabditis elegans spermatogenesis, asymmetric partitioning of c ellular components principally occurs via ER/Golgi-derived organelles, name d fibrous body-membranous organelles. In C, elegans spe-4 mutants, morphoge nesis of fibrous body-membranous organelle complexes is defective and sperm atogenesis arrests at an unusual cellular stage with four haploid nuclei wi thin a common cytoplasm. The spe-4 encoded integral membrane protein is a d iverged member of the presenilin family implicated in early onset Alzheimer 's disease. Specific antisera were used to show that SPE-4 resides within t he fibrous body-membranous organelles membranes during wild-type spermatoge nesis. Several spe-4 recessive mutants were examined for SPE-4 immunoreacti vity and a deletion mutant lacks detectable SPE-4 while either of two misse nse mutants synthesize and localize immunoreactive SPE-4 within their fibro us body-membranous organelles. One of these missense mutations is located w ithin a motif that is common to all presenilins. spe-4 mutants were also ex amined for other partitioning defects and tubulin was found to accumulate i n unusual deposits close to the plasma membrane, These results suggest that wild-type SPE-4 is required for proper localization of macromolecules that are subject to asymmetric partitioning during spermatogenesis.