Worm Breeder's Gazette 10(2): 85

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.

A Preliminary Molecular Analysis of glp-1

Judith Austin and Judith Kimble

Genetic studies have shown that glp-1 is necessary for at least two 
regulatory cell-cell interactions during C.  elegans development (
Austin and Kimble, 1987; Priess, Schnabel and Schnabel, 1987).  As a 
first step towards understanding the molecular mechanism by which glp-
1 affects these interactions, we have cloned the gene.  Our strategy 
relied on the fact that glp-1 maps 0.02% to the right of lin-12.  
Since the ratio of physical and recombinational distance in this 
region is about 830 kb/map unit (Greenwald et al.  1987), we estimated 
that the glp-1-lin-12 intergenic distance would be approximately 17kb. 
Therefore, we screened DNAs from 8 EMS and 2 gamma-ray induced glp-1 
alleles with two hybridization probes: T26E12, a cosmid that carries 
lin-12, and ZK506, a cosmid that overlaps and is to the right of 
T26E12 (both cosmids kindly provided by J.  Priess).  None of the glp-
1 alleles showed altered restriction fragment patterns when probed 
with T26E12 but 1/8 EMS and 2/2 gamma-ray induced alleles showed 
alterations in the same 1.5 kb R1 fragment when probed with ZK506.  
q172 has a 300bp deletion within the 1.5 kb R1 fragment, qDf2 has a 
large deletion with one endpoint in this fragment, and q339 has a DNA 
rearrangment where this fragment is replaced by novel fragments of 1.1 
and 1.9 kb.  At the same time, John Yochem, in Iva Greenwald's lab, 
had identified a sequence with strong similarity to the lin-12 
sequence (J.  Yochem and I.  Greenwald, personal communication; see 
also Yochem and Greenwald, this issue) that was then localized to 
ZK506 (J.  Sulston and A.  Coulson, personal communication).  Using a 
phage containing this lin-12 homologue as a probe for Southern blots 
of q172 and qDf2, we were able to determine that the DNA alterations 
associated with these two mutations lay within the region of 
similarity to lin-12.  In particular, the 1.5 kb R1 fragment is in a 
region that corresponds to the extracellular domain of lin-12 (J.  
Yochem and I.  Greenwald, personal communication).
On northerns, glp-1 probes hybridize to a single abundant transcript 
of 4.5 kb in the RNA of adult hermaphrodites.  This is the same size 
as the major lin-12 transcript (J.  Yochem and I.  Greenwald, personal 
communication).  Which raises the issue of whether crosshybridization 
is occurring.  We believe that we presently have gene specific 
hybridization but plan to test this using glp-1 and lin-12 alleles 
that produce transcripts of altered size.  Comparison of the level of 
glp-1 transcript in wildtype hermaphrodites and hermaphrodites where 
the germ line is absent suggests that the glp-1 message is located 
primarily in the germ line.  The presence of glp-1 message in the germ 
line is consistent with earlier results that indicated that glp-1 acts 
in the germ line to control the switch of germ cells from mitosis to 
meiosis (Austin and Kimble, 1987).