Worm Breeder's Gazette 9(1): 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 products of the unc-5 and unc-106 genes are required for correct dorsal/ventral positioning of longitudinal nerves and for dorsally- directed, circumferential growth of motor axons from cell bodies in the ventral hypodermis (1.2,3,4). In addition, the unc-106 product is required for ventrally-directed, circumferential growth of sensory axons from cell bodies in the lateral hypodermis (5). Certain non- neuronal cells (head mesodermal cell and excretory cell) with attachments to the body wall are also frequently displaced in unc-5 and unc-1O6 mutants. All of the mutant defects might be explained if the products of these genes mark dorsal/ventral position on the body wall or help decode such information. Recently, we observed that the reflexions of the hermaphrodite and male gonads are abnormal in unc-5 ( e53) and unc-106 (ev400) mutants. In normal development the anterior and posterior arms of the hermaphrodite gonad are produced by active migrations of the distal tip cells along the ventral body wall (6). Late in the third larval stage these cells make dorsal = clockwise turns (relative to the body wall, see Figure 2) to produce a mature gonad with the distal (reflexed) arms positioned dorsal to the proximal arms (Figure 1). In unc-5 and unc-106 mutants, the reflexions occur at the normal time. For about one half of the distal tip cells, the direction of turning is normal. In the remaining cases, however, the cells turn ventral = counterclockwise on the body wall to produce a mature gonad with the distal arms positioned lateral to the proximal arms (Figure 1). Similar mistakes are made by the linker cells in males of these mutants. The distal tip cells in hermaphrodites and the linker cell in males appear to be closely apposed to the body wall during gonad extension and reflexion (as judged by light microscopy). The position of reflexion may be determined by a timing mechanism as there is no apparent discontinuity on the body wall. The direction of reflexion, consistently dorsal = clockwise in wild type, appears to be random in unc-5 and unc-106 mutants. It is intriguing to speculate that the leading cells of the gonad contact the body wall to obtain some of the same positional information as used by the developing nervous system. We hope soon to examine these contacts by electron microscopy.