Worm Breeder's Gazette 10(2): 62
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
The membranous organelle (MO) is an unusual sperm-specific organelle which plays a number of critical roles in the differentiation of spermatozoa. During premeiotic and meiotic development, the fibrous body/membranous organelle (FB-MO) complex functions both as the site of assembly of many of the newly synthesized gene products and as a structure for organizing these components for localization and transport to the budding haploid spermatids. Later, the fusion of the mature MO with the back end of the cell during spermiogenesis adds important, new components to the cell surface of the crawling spermatozoa (Roberts et al., JCB 102: 1787, 1986). In spe-17 mutant spermatocytes, the normally ribosome free FB-MO complexes are uniformly associated with numerous ribosomes, some of which are transported into the normally ribosome free, haploid spermatids. These ribosomes probably contribute to the abnormal appearance of the RNA-containing perinuclear halo in the spe-17 mutant spermatids. In addition, the spermatids are abnormally small, and the proper organization of their organelles is disrupted which suggests that a common cytoskeletal defect may be responsible for the various abnormalities. Despite these abnormalities, spe-17 spermatids form crawling spermatozoa which are capable of translocating across a surface. In spe-10 mutant spermatocytes, the FB-MO complexes disassemble prematurely during meiosis rather than in the newly budded spermatids. Membraneless FBs are commonly found left behind in the residual body, and in many cases, they bud off as small cytoplasts. The normal folding of the MOs into their compact spermatid morphology is also disrupted, and large, vaculated MOs are seen in more than 40% of the cells. These defects suggest that the FB must be associated with the MO membrane for proper segregation to the spermatids during meiosis and that proper MO folding may require structural or enzymatic cues from the FB. These vaculated MOs are segregated to the spe-10 spermatids. All spe-10 spermatids, regardless of the severity of their MO defects, are abnormal in their size and organelle organization. The spermatids with less severe MO defects can form spermatozoa, but these spermatozoa, like those of fer-1, fail to fuse their MOs and translocate.