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.

Analysis of Two Loci Required for the Normal Morphology and Cellular Localization of a Unique Organelle in Sperm

Diane C. Shakes and S. Ward

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 
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.