Worm Breeder's Gazette 15(1): 58 (October 1, 1997)
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.
Department of Biology, Technion-Israel Institute of Technology Haifa-32000, Israel.
Cell interactions, fusions and migrations are processes involved in the formation of organs. In C. elegans these have been widely reported to occur in the formation of the hypodermis, uterus, excretory gland cells, pharynx and vulva. We have been studying the formation of the vulva in C. elegans by characterizing the pattern of cell recognitions, migrations and fusions by using immunofluorescent techniques and confocal microscopic reconstructions. Vulval sections at different times during the developmental process were stained for MH27, an adherens junction protein (1). Events have been followed from the time the fates of the six vulval precursor cells (VPCs) have been specified (27 hours; times are in hours after hatching), the generation of the VPC daughters (30 hours), VPC grand-daughters (32 hours; late L3), which results in 22 epithelial cells of the vulval lineage (34 hours) to the construction of a tube that consists of seven toroidal rings stacked together. These rings are designated as: vula, vulb1, vulb2, vulc, vuld, vule and vulf (2). These studies have revealed a definite pattern and order of cell migrations and fusions which allow us to propose a pathway for vulval morphogenesis, with the following intermediates being identified till now : In the first stage a vulval primordium consisting of a longitudinal row of 12 cells (after two rounds of division), shows no signs of differentiation (Fig.1A) followed by a stage where the six central cells are polarized towards the center of symmetry before the last round of division (Fig.1B). During the third and final round of divisions six cells divide transversely, two cells do not divide and four divide longitudinally (3), (Fig.1C). This intermediate shows a central ring precursor containing four cells (vulf), four more that form the next ring (vule) and a third ring (vuld) with two cells. The next two cells (!c!) on each side have divided and are sending processes towards the centre of symmetry of the vulva surrounding vuld. The last schematic intermediates (Figs. 1D-H) show the seven rings that have completed the migrations and are in different stages of cell fusions starting with an intermediate where all seven rings are unfused followed by several intermediates: Fig.1D-rings vula and vulc are partially fusedand contain two binucleate cells each, Fig.1E-vuld has fused, Fig.1F-vula and vulc have fused, Fig.1G-vulf has fused, Fig.1H-vule has fused. These events studied in time thus reveal a pathway for vulva formation in C. elegans. 1. Podbilewicz, B. and White, J.G. (1994). Dev.Biol. 161, 408-424. 2. White, J.G. Personal Communication. 3. Sulston, J.E. and Horvitz, H.R. (1977). Dev. Biol. 56, 110-156.