Worm Breeder's Gazette 14(1): 95 (October 1, 1995)

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.


Sambath Chung, and Monica Driscoll,

Department of Molecular Biology and Biochemistry, Rutgers University, New Brunswick, NJ 08855

The mechanisms of cell killing in programmed cell
death (ced-3- and ced-4-mediated) and degenerative
cell death (for example, mec-4(d)-mediated death of
the touch receptor neurons) are genetically and
morphologically distinct.  However, we have found
that one of the final stages of programmed and
degenerative death pathways--the removal of
corpses--occurs, at least in part, by a common
The completion of a study of the ultrastructural
changes occurring during the time course of mec-
4(d)-induced death (see wm95 p188) lead us to
wonder how degenerative cell death corpses were
eliminated and whether any known "undertaker"
genes, such as the engulfment ced genes, were
involved.  ced genes needed for efficient removal
of PCD corpses appear to act in two parallel
pathways (one includes ced-1, ced-6, and ced-7; the
other ced-2, ced-5, and ced-10; see Ellis et al.
1991 Genetics 129:79).  Since the persistence of
mec-4(d)-induced touch cell corpses had not been
examined under conditions in which both pathways
operative in programmed cell death corpse removal
were inactivated, we constructed the triple mutant
ced-7(n1892); ced-5(n1812); mec-4(u231).
Strikingly, degenerative death corpses persist this
strain.  For example, in one comparison of L3 stage
animals, we found that 71% of ced-7; ced-5; mec-
4(d) animals still had vacuolar degeneration in the
tail whereas only 2% of ced(+); mec-4(d) animals
exhibited vacuoles in the tail at this stage.
Thus, ced-5, ced-7, or both appear necessary for
efficient removal of touch cell corpses.
To investigate which individual ced genes were
involved and to ask if one or both corpse removal
paths were involved, we looked at persistence of
degenerative cell death corpses in individual ced;
mec-4(u231) double mutants.  The following data
were recorded:
Strain                                   L2     L3
mec-4(u231)                              17%    2%
ced-1(e1735); mec-4(u231)                38%    9%
ced-6(n2095); mec-4(u231)                54%   14%
ced-7(n1892); mec-4(u231)                48%   16%
ced-2(e1752); mec-4(u231)                52%   34%
ced-5(n1812); mec-4(u231)                65%   56%
ced-10(n1993); mec-4(u231)               45%   22%
ced-7(n1892); ced-5(n1812); mec-4(u231)  87%   71%
Thus, preliminary data suggest that 1) all
engulfment ced genes contribute somewhat to the
removal of degenerative corpses, 2) genes ced-2,
ced-5, and ced-10 play the most important role.
The latter finding is interesting because ced-2,
ced-5, and ced-10 have been found to be required
for lin-24(sd)- and lin-33(sd)-induced
"degenerative" Pn.p deaths (S. Kim and R. Horvitz,
see also wm91 p188).