The Caenorhabditis elegans gene lin-26 can trigger epithelial differentiation without conferring tissue specificity

How epithelial cell fates become specified is poorly understood. We have pr eviously shown that the putative C2H2 zinc-finger transcription factor LIN- 26 is required for the differentiation of ectodermal and mesodermal epithel ial cells in Caenorhabditis elegans. Here, we report that ectopic LIN-26 ex pression during early gastrulation transforms most blastomeres into epithel ial-like cells. Specifically, LIN-26 induced the expression of three epithe lial markers: the adherens junction protein JAM-1; DLG-1, which is essentia l for the assembly of JAM-1 at junctions; and CHE-14, which is involved in apical trafficking. Furthermore, ultrastructural studies revealed that ecto pic LIN-26 expression induced the formation of adherens-like junctions. How ever, ectopic lin-26 expression did not confer any tissue-specific cell fat e, such as the epidermal cell fate, as evidenced from the observation that several epidermal-specific genes were not induced. Conversely, we show that epidermal cells displayed some polarity defects in lin-26 mutants. We conc lude that lin-26 can induce epithelial differentiation and that epithelioge nesis is not a default pathway in C. elegans. (C) 2001 Academic Press.