Cell–cell communication: Receptor function at the junction

The induction of the vulva of the nematode Caenorhabditis elegans is today recognized as one of the premier systems for studying receptor tyrosine kinase function. More than 40 genes have been identified that modulate intercellular signaling during vulval induction, most have been sequenced, and it is clear that the modus operandi of this signal transduction pathway is highly similar to that of its counterparts in other multicellular organisms [1,2] (Fig. 1). Contrast this with the situation at the beginning of 1990, when Kim and Horvitz [3] reported, with evident consternation, that the sequence of lin-10, a gene essential for vulval induction, revealed no obvious similarity to any previously cloned gene from any organism.