Program of the 2001 International Worm Meeting - Sternberg Lab ...

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220. Variations in pattern formation
and cell specification during
nematode embryogenesis
Vera Lahl, Magdalena Laugsch,
Einhard Schierenberg
Zoologisches Institut, Universität Köln, 50923
Köln, Germany
We have found that the cephalobid nematode A.
nanus expresses considerable differences in the
pattern of cell specification and spatial
arrangement of cells during early
embryogenesis compared to C. elegans
(Wiegner and Schierenberg, Dev. Biol.,1998,
1999). Based on these results we have begun to
analyze other free-living and parasitic
nematodes in this respect.
Here we report our findings on representatives
belonging to the same family as C. elegans
(Rhabditidae). We find major differences in the
duration of cell cycles, early zygotic
transcription, cellular pattern formation and
cell-cell interactions required for proper fate
assignment. In contrast, species with only
distant relationship to C. elegans may
nevertheless show more similarities in this
respect. This indicates that variations cannot be
explained by phylogenetic position alone. We
suggest that the observed differences reflect
alternative developmental strategies going along
with the occupation of different ecological
niches.
221. Metaphase-to-anaphase
transition-defective mutants occur in
Anaphase Promoting Complex genes
and exhibit phenotypes in both
oocyte and spermatocyte meiosis in
C. elegans.
Edward S. Davis 1 , Amanda
Pletcher 2 , Donald Fox 1 , Barry
Chestnut 1 , Diane C. Shakes 2 , Andy
Golden 1
1 NIDDK, National Institutes of Health,
Bethesda, MD USA
2 College of William and Mary, Williamsburg,
VA
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The Anaphase Promoting Complex or
Cyclosome (APC/C) is a multisubunit ubiquitin
ligase, which causes the destruction of
cell-cycle regulators leading to the segregation
of chromosomes at anaphase and exit from
mitosis and meiosis. Previously, we described
32 temperature-sensitive C. elegans mutants that
defined five genes, three of which were novel.
At the non-permissive temperature of 25
degrees, all 32 mutant adults produce embryos
arrested at the 1-cell embryonic stage, with their
sperm and oocyte chromatin highly condensed,
while polar bodies are absent. The phenotypes
of these mutants indicates that they are arrested
at the metaphase-to-anaphase transition of
meiosis I in oocytes. We termed the three novel
genes "mat" (metaphase-to-anaphase
transition-defective). In addition, each mat gene
is represented by some alleles that exhibit
germline mitotic and somatic defects.
Genetic mapping demonstrated that all three mat
genes mapped near C. elegans orthologs of APC
subunits. To reveal the molecular identity of
these genes, we determined the DNA sequences
of the appropriate APC subunit genes in several
alleles of each complementation group. The
results indicate that in all cases, a given mat
mutation occurred in the predicted APC subunit
gene. Further, RNA interference using the
predicted APC subunit genes gave the same
1-cell meiotic arrest phenotype as the mutants at
the non-permissive temperature. We conclude
that mat-1, mat-2, and mat-3 are all alleles of C.
elegans APC subunit genes.