Worm Breeder's Gazette 7(2): 27

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More Antibodies to Germ-line-specific Granules in C. elegans

S. Strome

Figure 1

In the last newsletter I reported the finding of several commercial 
preparations of rabbit and goat IgG that fortuitously stain granules 
unique to the germ line (P granules) in C.  elegans.  Several 
additional antibody preparations have now been generated.  From a 
screen of 26 rabbits from the wilds of Arvada, Colorado, the serum 
from 2 rabbits contains anti-P-granule antibodies.  A hybridoma cell 
line that secretes IgG directed against P granules was obtained by 
immunizing mice with C.  elegans egg homogenate and screening the 
resulting antibodies by immunofluorescence microscopy on fixed C.  
elegans eggs.  Several new hybridomas that synthesize anti-P-granule 
antibodies are presently being cloned.  Hopefully, at least some of 
these antibodies are directed against different determinants on P 
Mutants that show defects in the early embryonic clevage patterns 
are being used to determine whether the position and orientation of 
the mitotic spindle and cleavage furrow are involved in granule 
segregation.  A wild-type zygote divides transversely and 
asymmetrically.  Zyg-9 (b244) zygotes divide first longitudinally and 
then transversely (see below).  Despite the altered orientation of the 
spindle and cleavage furrow, P granules are localized at the posterior 
pole of the embryo and thus are distributed to both of the resulting 
blastomeres.  This result suggests both that P granules do not 
segregate with one nucleus or one half-spindle and that the positional 
information responsible for P-granule segregation is separate from the 
positional information that orients the spindle and cleavage furrow.
Zyg-11 (b2) zygotes exhibit variable positioning of the first 
cleavage plane, as shown below.  The localization of P granules in zgy-
11 embryos is also variable and difficult to interpret.  In a strain 
carrying mn40, an amber allele of zgy-11, a large percentage of early 
embryos have P granules localized at the end of the embryo next to the 
polar body, which in wild-type embryos is almost always anterior.  It 
is not known whether in these zgy-11 embryos the polarity of the whole 
embryo is reversed relative to the polar body, or whether P granules 
are segregated to the wrong end of the embryo.  In many of the 
symmetrical 2- and 4-cell zgy-11 embryos, P granules are found in all 
of the cells.  These results support the suggestion that this mutant 
is defective in the establishment of polarity (see Wolf, Kemphues, 
Wood & Hirsh, this issue).
To complement these mutational manipulations, C.  elegans embryos 
are being treated with inhibitors of microtubule- and microfilament- 
mediated processes to investigate the possible roles of these 
cytoskeletal components in P-granule movement.
[See Figure 1]

Figure 1