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.


Ranjana Sharma-Kishore, Benjamin Podbilewicz

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.