Volume 17, Number 3,
Issue of February 1, 1997
pp. 1033-1045
Copyright ©1997 Society for Neuroscience
Neuropathology of Degenerative Cell Death in
Caenorhabditis elegans
Received July 9, 1996; revised Nov. 12, 1996; accepted Nov. 26, 1996.
David H. Hall1,
Guoqiang Gu2,
Jaime García-Añoveros2,
Lei Gong3,
Martin Chalfie2, and
Monica Driscoll3
1 Department of Neurosciences, Albert Einstein College
of Medicine, Bronx, New York 10461, 2 Department of
Biological Sciences, Columbia University, New York, New York 10027, and
3 Department of Molecular Biology and Biochemistry, Rutgers
University, Piscataway, New Jersey 08855
In Caenorhabditis elegans necrosis-like neuronal
death is induced by gain-of-function (gf)
mutations in two genes, mec-4 and deg-1,
that encode proteins similar to subunits of the vertebrate amiloride-sensitive epithelial Na+ channel. We have
determined the progress of cellular pathology in dying neurons via
light and electron microscopy. The first detectable abnormality is an
infolding of the plasma membrane and the production of small
electron-dense whorls. Later, cytoplasmic vacuoles and larger
membranous whorls form, and the cell swells. More slowly, chromatin
aggregates and the nucleus invaginates. Mitochondria and Golgi are not
dramatically affected until the final stages of cell death when
organelles, and sometimes the cells themselves, lyse. Certain cells,
including some muscle cells in deg-1 animals, express
the abnormal gene products and display a few membrane abnormalities but
do not die. These cells either express the mutant genes at lower
levels, lack other proteins needed to form inappropriately functioning
channels, or are better able to compensate for the toxic effects of the
channels. Overall, the ultrastructural changes in these deaths suggest
that enhanced membrane cycling precedes vacuolation and cell swelling.
The pathology of mec-4(gf) and deg-1(gf)
cells shares features with that of genetic disorders with alterations
in channel subunits, such as hypokalemic periodic paralysis in humans
and the weaver mouse, and with degenerative conditions,
e.g., acute excitotoxic death. The initial pathology in all of these
conditions may reflect attempts by affected cells to compensate for
abnormal membrane proteins or functions.
Key words:
neurodegeneration;
Caenorhabditis elegans;
degenerin;
mec-4;
deg-1 neuropathology;
necrosis;
membrane cycling