THE C-ELEGANS GENE LIN-44, WHICH CONTROLS THE POLARITY OF CERTAIN ASYMMETRIC CELL DIVISIONS, ENCODES A WNT PROTEIN AND ACTS CELL NONAUTONOMOUSLY

Mutations in the C. elegans gene lin-44 lead to reversals in the polar ity of certain asymmetric cell divisions. We have discovered that lin- 44 is a member of the Wnt family of genes, which encode secretory glyc oproteins implicated in intercellular signaling. Both in situ hybridiz ation experiments using lin-44 transcripts and experiments using repor ter constructs designed to mimic patterns of lin-44 expression indicat e that lin-44 is expressed in hypodermal cells at the tip of the tail and posterior to the cells with polarities affected by lin-44 mutation s. Our mosaic analysis indicates that lin-44 acts cell nonautonomously . We propose that LIN-44 protein is secreted by tail hypodermal cells and affects the polarity of asymmetric cell divisions that occur more anteriorly in the tail.