Worm Breeder's Gazette 12(3): 85 (June 15, 1992)

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.

Localization of the glp-1 Protein in the Germline and Embryos

Sarah Crittenden, Judith Kimble

Laboratory of Molecular Biology, University of Wisconsin-Madison

The glp-1 protein mediates at least two cell interactions during C. elegans development (for review see ref .1) . We have used affinity purified rat polyclonal antibodies to glp-1 fusion proteins to look at the glp-1 protein during germline development and embryogenesis. We find that glp-1 protein is membrane associated and is present at the times and places that its activity is required.

In the germline, zygotic glp-1 activity is required for mitosis during larval development and adulthood. In hermaphrodites, all germ cells are mitotic through L1 and L2 ,proximal germ cells enter meiosis during L3 .This pattern of distal mitosis and proximal meiosis is maintained throughout L4 and adulthood. We first detect the glp-1 protein when there are 4-8 germ cells in L1 'sand see its expression continue in cells that are known to be mitotic throughout larval development and adulthood. In mitotic cells, glp-1 protein is always membrane associated. The level of glp-1 protein is very low in distal meiotic cells and is undetectable in differentiating cells and mature gametes. This germline pattern of glp-1 expression supports the idea that the glp-1 protein is required in the membranes of the mitotic cells to receive and transduce a signal from the distal tip cell. The lack of glp-1 protein in oocytes also indicates that maternal glp-1 mRNA, not protein, is contributed to embryos.

In embryos, maternal glp-1 is required at the 4-28 cell stage for proper morphogenesis and for an interaction between ABa and EMS and/or their descendents for induction of anterior pharynx. We first detect membrane associated glp-1 protein at the four cell stage, where the protein appears to be localized to ABa and ABp. The staining is strongest at regions of cell cell contact. The protein remains localized, possibly to the AB descendents through approximately the 28 cell stage. After this the staining is greatly reduced or nonexistent until late embryogenesis. This expression pattern suggests that glp-1 protein is required in ABa (and its descendents?) to receive an inductive signal from EMS (and its descendents?). The role of glp-1 in the ABp blastomere is not clear. Since ABa and ABp are initially equivalent (2), it is an intriguing possibility that glp-1 might mediate lateral signalling between these two blastomeres and/or their descendents causing them to adopt distinct fates. Alternatively, glp-1 might be involved in inductive interactions between ABp and EMS or P2 and/or their descendents. Lack of these interactions may be the basis of embryonic lethality in glp-1 (lf)embryos.

Literature Cited:

1. Lambie, E. J. and Kimble, J., 1991, Annu. Rev. Genet. 25:411-436

2. Priess, J.R. and Thomson, J.N., 1987, Cell 48:241-250.