Worm Breeder's Gazette 4(1): 33

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.

Cell Lineages and Developmental Defects of Temperature-sensitive Abnormal Embryogenesis Mutants in C. elegans

E. Schierenberg, J. Miwa, G. von Ehrenstein

We have described 11 temperature-sensitive abnormal embryogenesis 
mutants (Miwa et al.).  Here we describe the cellular phenotype of 
these mutants at the permissive (16 C ) and non-permissive temperature 
(25 C ), including the temperature-sensitive phase of embryogenesis, 
visible developmental defects and cell lineages (time and direction of 
cell divisions and cell migrations at 16 C and 25 C ) at least to the 
50-cell stage (or stage of arrest).  All but one mutant have visible 
developmental defects at 25 C before the stage of arrest.  The six 
mutants that arrest at the beginning of the morphogenesis phase (
between the lima bean and tadpole stages) have defective developmental 
events or abnormal cell lineages before the 50-cell stages, yet they 
continue developing abnormally for several hours.  Some mutants also 
have visible defects at 16 C.  The overall division rate of the stem-
cell lines of the mutants at 25 C (excluding the 2 one-cell stage 
stoppers and the osmotically sensitive mutant) is faster than in the 
wild-type in 2 mutants, slower in 5 mutants, and equal to the wild-
type in one mutant.
The temperature-sensitive phase of embryogenesis (TSPh), as defined 
by shift-up experiments of eggs in different stages, for 5 maternal 
mutants (4 genes, emb-1, emb-6, 
ore the two-cell stage, and in 4 mutants (3 
genes, emb-2, emb-9) the TSPh ends during 
embryogenesis; the TSPh for 2 mutants (genes emb-4, 
t be determined because the eggs did not 
survive handling for microscopy.
Both alleles in gene emb-5 (maternal) have a defective gastrulation (
time of E-cell migration and time and direction of E-cell division) 
and they arrest around the lima bean stage.  The TSPh of one allele 
ends at the 12-cell stage and that of the other ends at the 50-cell 
stage.  The severity of the gastrulation defect is also different in 
the two mutants.
The TSPh of the only zygotic mutant (emb-9) is between the comma and 
the early pretzel stage, and it stops in the pretzel stage without any 
visible abnormality.  The cell lineage of this mutant at 25 C is 
normal to the 100-cell stage and it has no visible defects up to this