The C.elegans vulva is formed from the descendants of the P cells. The 12 P cells, born early in embryogenesis, migrate into the ventral midline by the L1 larval stage where they divide to give an anterior Pn.a neuroblast and a posterior Pn.p hypodermal cell. Of the 12 Pn.p cells, six (P3.p - P8.p) form the vulval equivalence group and are called the vulval precursor cells. On induction by the anchor cell, P5.p, P6.p and P7.p adopt induced cell fates and divide to generate the 22 cells that form the vulva.
pvl-5 (
ga87) was isolated in a screen for genes affecting the development of the vulva (WBG 13.1,
p69). In
ga87 animals, there is an average of 7.1 Pn.p cells present in the ventral midline as opposed to 12 Pn.p cells in wildtype. Most probably
ga87 is a null mutation as the phenotype of
ga87/mnDf39 is no worse than
ga87 alone. An additional allele of
pvl-5 has been isolated in an F1 non-complementation screen and is being characterized.
pvl-5 has been mapped to a small region covered by the deficiency mnDf39 on LGII. The cloning of
pvl-5 by cosmid rescue is underway. We do not know why there are too few Pn.p cells in
ga87 . It could be either due to a loss of P cells or Pn.p cells by cell death, a failure of P cells to migrate into the ventral midline or a Pn.p to Pn.a cell fate transformation. To distinguish between these possibilities I will use
unc-4::gfp which is expressed in the neurons derived from the Pn.a cells (David M. Miller III and Charles J. Niemeyer, Development 121, 2877-2886). In the case of a hypodermal (Pn.p) to a neuroblast (Pn.a) cell fate transformation there will be more
unc-4::gfp expressing cells in the ventral nerve cord. If there is a loss of P cells or a failure to migrate there might be fewer
unc-4::gfp expressing cells in the VNC. If
pvl-5 affects the maintenance of Pn.p cells alone there would be no change in the number of cells expressing the marker. I will also study the P and Pn.p cells using
jam-1::gfp (gift of Jeff Simske).
jam-1 codes for the protein recognized by the MH27 antibody and hence JAM-1::GFP outlines the boundaries of hypodermal cells. The fate of P cells and their lineage will be followed in a
pvl-5(
ga87);
jam-1::gfp strain. Further results from these experiments will be presented.