Vulva morphogenesis involves attraction of plexin 1-expressing primordial vulva cells to semaphorin 1a sequentially expressed at the vulva midline.
Vulva development in C. elegans involves cell fate specification followed by a morphogenesis phase in which homologous mirror image pairs within a linear array of primordial vulva cells form a crescent shape as they move sequentially towards a midline position within the array. The homologous pairs from opposite half vulvae in fixed sequence fuse with one another at their leading tips to form ring-shaped (toroidal) cells stacked in precise alignment one atop the other. Here, we show that the semaphorin 1a SMP-1, and its plexin receptor PLX-1, are required for the movement of homologous pairs of vulva cells towards this midline position. SMP-1 is upregulated on the lumen membrane of each primordial vulva cell as it enters the forming vulva and apparently attracts the next flanking homologous PLX-1-expressing vulva cells towards the lumen surface of the ring. Consequently, a new ring-shaped cell forms immediately ventral to the previously formed ring. This smp-1- and plx-1-dependent process repeats until seven rings are stacked along the dorsoventral axis, creating a common vulva lumen. Ectopic expression of SMP-1 suggests it has an instructive role in vulva cell migration. At least two parallel acting pathways are required for vulva formation: one requires SMP-1, PLX-1 and CED-10; and another requires the MIG-2 Rac GTPase and its putative activator UNC-73.
Dalpé
Gratien
G
Samuel Lunenfeld Research Institute of Mount Sinai Hospital, 600 University Avenue, Toronto M5G 1X5, Canada.
Brown
Louise
L
Culotti
Joseph G
JG
D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D039961:Semaphorins / Q000235:genetics / Q000378:metabolism*; D014844:Vulva / Q000196:embryology*; D018631:ras Proteins / Q000378:metabolism
D029742:Caenorhabditis elegans Proteins; D009419:Nerve Tissue Proteins; D011956:Receptors, Cell Surface; D039961:Semaphorins; C111263:UNC-73 protein, C elegans; C492117:plx-1 protein, C elegans; D018631:ras Proteins