Worm Breeder's Gazette 11(5): 71

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.

Maternal Effect Lethal Mutants Lacking Gut Granules

Jocelyn Shaw, Theresa Stiernagle and Chris Sigurdson

Using the screen for maternal effect lethal mutants developed by Ken 
Kemphues and Jim Priess, we have been looking for mutants whose 
inviable progeny fail to make gut granules in a manner similar to that 
described by Diane Morton et al (WBG Vol.  10 #2).  With this screen 
we hope to identify mutations in genes that are required for proper 
specification of the E lineage.  The mutants that we retain from the 
screen have inviable progeny that divide to >200 cells (approx), are 
not multinucleate, and do not make gut granules as detected under 
polarized light.
The mutants that we recover from this screen have fallen into three 
classes: par mutants (par-1, par-3, 
by Kemphues et al.); those that 
we are unofficially calling gut mutants (gut defective); and those 
that we are unofficially calling ggl (gut granuleless).  We have 
concentrated on characterizing mutants of the gut and, to some extent, 
the ggl classes.  From screens of approximately 32,000 EMS-treated 
haploid genomes and 16,000 gamma-irradiated haploid genomes we have 
recovered 13 gut mutants and 4 ggl mutants.  We have also obtained 3 
mutants of the gut class from Diane Morton with whom we are 
collaborating to characterize this class of mutant.  The combined set 
of gut mutants contains mutations in at least 10 different 
complementation groups with only two genes represented by more than 
one allele.  The ggl class of mutant is represented by four alleles in 
a single complementation group.
The classification of mutants is based on observations of both early 
embryogenesis and the terminal phenotype in progeny of mutant 
hermaphrodites.  Embryos of gut mutants divide in a normal asymmetric 
and asynchronous pattern during very early cell divisions, thus 
distinguishing them from par mutants.  P granules are also segregated 
normally.  Embryonic cell divisions in these embryos appear to be 
fairly normal in timing and pattern until the beginning of 
gastrulation.  At that time in wild-type development the two E cells' 
division rate slows and the E cells begin to move into the center of 
the embryo.  In gut mutants the E cells' division rate does not slow 
and the E. coli's do not gastrulate.  These embryos arrest development 
embryonically as a ball of cells (approx.  400-600 nuclei) with no 
apparent morphogenesis.  As well as lacking gut granules, the embryos 
fail to produce two antigens that are normally found in differentiated 
gut cells (assayed by antibodies J126 and SP37 from S.  Strome).  They 
do undergo some differentiation; we observe cell-death nuclei, 
neuronal nuclei, and large amounts of MyoB (anti-myoB from D.  Miller).
In embryos of ggl mutants early divisions including E cell division 
and gastrulation appear to be normal.  Although these embryos fail to 
produce gut granules they do make significant amounts of the gut-
specific products recognized by SP37 and J126.
Since we believe that at least some of the gut genes are most 
specifically involved in proper specification of the E lineage we are 
concentrating on further characterizing these genes genetically and