Temperature-sensitive mutations in Caenorhabditis elegans : a sterile mutation affecting oocyte I core relations

A temperature sensitive sterile mutant of C . elegans (Sis2) was studied. This monofactorial, Mendelian, autosomic, semi-dominant mutation was thermosensitive between the beginning of the pachytene stage and that of the dialrinetic stage. Light and electron microscopy demonstrated the lack of membranes between newly formed oocytes, and between these oocytes and the rachis. These cellular membranes appear again towards the end of the pachytene stage. They delimit anucleated or multinucleated cytoplasmic islets of varying sizes rather than a normal anucleated rachis. Beyond the ootestis loop, during cytoplasmic growth, oocytes are individualized but contain a large number of pseudo-pachytene nuclei. Autoradiography showed incorporation of tritiated uridine in pachytene cells but not in multinucleated growing oocytes of S,ts mutants, although the nuclei remained in pseudo-pachytene nuclei. The regulation of membrane synthesis necessary to the maturation of pachytene cells (associated to the rachis) into diakinesis oocytes 1, appears to,be affected by this mutation.