Worm Breeder's Gazette 8(2): 14

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.

Genetic Approach to Studying P-granule Function

S. Strome, W.B. Wood

One approach to analyzing the function of germline granules (P 
granules) in C.  elegans is to isolate and characterize mutants in 
which they are altered or lacking.  We predict that if they are 
required during development, worms lacking functional P granules will 
be sterile.  To test this, we are using a genetic scheme devised by 
Jim Preiss to obtain sterile mutants.  [Mutations at the lin-2 locus 
result in defective vulvae.  Fertile lin-2/lin-2 hermaphrodites cannot 
lay their eggs and as a result are consumed by their progeny.  However,
sterile lin-2/lin-2 worms do not produce progeny and therefore 
survive.]  We are examining these sterile worms for alteration or 
absence of P granules, by immunofluorescence staining with an anti-P-
granule monoclonal antibody (MApK76).  From the first mutagenesis of 
lin-2/lin-2 worms, done in collaboration with Ken Kemphues and Nurit 
Wolf, a P-granule mutant was isolated.
The mutant has been characterized as follows: 1) The P-granule 
defect was separable from the mutation(s) causing sterility.  Mutant 
worms that do not stain with MAbK76 appear morphologically normal and 
are fertile.  2) Although P-granule staining is not detected with 
MAbK76, two other anti-P-granule MAb's (M629 and L416) do stain P 
granules, as do some anti-P-granule sera.  Thus the mutation seems to 
result in loss or alteration of the antigenic determinant or the P-
granule component recognized by MAbK76.  These results indicate that 
at least some of the anti-P-granule antibodies recognize different 
antigenic determinants and that the K76 determinant in its normal 
state is not required for germ-cell development.  Immunoprecipitations 
from wild-type vs.  mutant worm homogenates are in progress to 
determine whether any of the putative P-granule polypeptides are 
altered or missing in mutant worms.  3) The mutation is recessive; 
worms heterozygous for the mutation stain positively with MAbK76.  4) 
The mutation has been outcrossed and assigned to linkage group IV; 
further crosses are in progress to map the mutation.
We have used the P-granule mutant to determine how long maternal P-
granule material (specifically K76 antigen) present in oocytes 
persists in embryos.  This was done by examining homozygous mutant 
embryos produced by hermaphrodites heterozygous for the mutation.  
Maternal P granules persist throughout embryogenesis and into the 
first larval stage (L1).  New P-granule material (K76 antigen) begins 
to be synthesized in L1's, when the two germ-line precursor cells 
start to proliferate.  This was determined by examining heterozygous 
embryos and larvae produced by mating homozygous mutant hermaphrodites 
with wild-type males.