Connection of vulval and uterine epithelia in Caenorhabditis elegans

In the Caenorhabditis elegans hermaphrodite, the establishment of the egg-laying system requires the connection of two epithelial tubes: the uterus of the gonad and the vulva in the underlying ectoderm. A specialized uterine cell, the anchor cell (AC), plays a central role in specifying the fates of the uterine and vulval precursor cells via the EGF-Ras-MAP kinase and the Notch/Delta signaling pathways. This central and common inducing source ensures that the two sets of cells are in register and it specifies the cell types that build the T-shaped connection between uterus and vulva. On either side, progeny of the induced cells form lumen structures and undergo stereotyped cell-to-cell fusion, thereby building epithelial tubes. Finally, the anchor cell fuses with a uterine syncytium and thus leaves only a thin cellular process between the lumen of the uterus and the vulva. In the adult, the fertilized eggs exit the lumen of the uterus through the vulva. This relatively simple developmental process serves as a model to study the biology of cells during organogenesis, such as intercellular signaling, cell polarity, invasion of basal laminae and epithelia, cell recognition and cell fusion. The anchor cell is a particularly interesting cell as it coordinates the development of its neighboring cells by using different signaling pathways at different times.