Worm Breeder's Gazette 13(3): 25 (June 1, 1994)

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.

Asymmetric PAR-2 at First Cleavage

Lynn Boyd[1], Diane Levitan[2], Ken Kemphues[1]

[1]Section of Genetics and Development, Cornell University
[2]Department of Cellular and Developmental Biology, Harvard University (current address: Columbia University)

The six par genes are required for normal embryonic development of C. elegans. Analysis of the mutant phenotypes suggests that these genes function in establishing asymmetry in the one cell embryo. For example, mutations in the par genes can disrupt the normal asymmetric first cleavage and the asynchrony of the second cleavage division as well as other asymmetries between the P1 and AB blastomeres.

Molecular isolation of the par-2 gene now provides us more information towards possibilities for the activity of the gene product. The predicted PAR-2 protein contains two recognizable motifs: a region similar to ATP-binding domains in other proteins and a second region with similarity to a newly recognized class of putative zinc binding proteins. We are very interested in the role of this motif and whether it might be involved in interactions with other macromolecules during the establishment of asymmetries.

Immunolocalization of PAR-2 protein using affinity purified rabbit polyclonal antibodies reveals two interesting aspects of its subcellular localization. First, in wild type worms antibodies to PAR-2 stain at the cell periphery in the distal arm of the gonad and in developing oocytes. The pattern of staining is very similar to the actin distribution in the gonad. Immediately after fertilization localized staining is no longer detected. We would like to determine whether the lack of detectable staining after fertilization is due to loss of the protein or a redistribution of PAR-2 .Second, a very interesting aspect of the staining appears later in the first cell cycle when the peripheral staining reappears, but is restricted to the posterior half of the cell. This posterior localization of PAR-2 is consistent with a role in establishing or maintaining polarity during the first cell cycle.

The posterior localization of PAR-2 raises several interesting questions. We are interested in understanding how this localization is important for the function of par-2 ,and how this localization is achieved. Since all the par genes are involved in generating early asymmetries and PAR-2 shows an asymmetric distribution, we wanted to know how PAR-2 localization is affected by mutations in the other 5 par genes. In antibody stains of other par mutants, PAR-2 shows an apparently normal peripheral localization in oocytes and embryos. Interestingly, the posterior localization is disrupted in par-3 and par-6 mutant embryos, but normal in the other mutants.