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.

Abnormal Gonadal Reflexion in unc-5 and unc-106 Mutants

E. Hedgecock

Figure 1

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.

Figure 1