Reciprocal changes in expression of the receptor lin-12 and its ligand lag-2 prior to commitment in a C. elegans cell fate decision.

During development of the C. elegans hermaphrodite gonad, two cells interact with each other, so that one chooses to become the anchor cell (AC) and the other becomes a ventral uterine precursor cell (VU). This interaction is mediated by the receptor LIN-12 and its apparent ligand LAG-2. We show that initially lin-12 and lag-2 are expressed in both cells, but prior to commitment, the expression patterns change in a reciprocal manner, so that lin-12 expression becomes restricted to the presumptive VU and lag-2 expression becomes restricted to the presumptive AC. In addition, lin-12 activity promotes expression of lin-12 and represses expression of lag-2. Furthermore, we show that positive autoregulation of lin-12 transcription in the presumptive VU is mediated by a cis-acting 5' regulatory sequence and is necessary to specify the VU fate. Our results suggest that transcriptional control is a component of the feedback mechanism involved in specifying the AC and VU fates.