Asymmetric cell division is a fundamental process that produces celler diversity during development. In C. elegans, asymmetric divisions of certain blast cells, including the T blast cell, are regurated by
lin-17/frizzled and
lin-44/wnt. It has been proposed that the LIN-44 signal, which acts through the LIN-17 receptor, provides polarity to cells that undergo asymmetric division. To make clear this model, we expressed
lin-44 ectopically, and examined effects on asymmetric cell division. In normal development, the anterior daughter of the T cell produces hypodermal cells, and the posterior daughter produces neural cells. In
lin-44 mutants, however, the anterior daughter produces neural cells, and the posterior daughter produces hypodermal cells. That is,
lin-44 mutations freqently reverse the polarity of the division ( 70% ). As a result of expression of
lin-44 at the anterior of the T cell in
lin-44 mutants, polarity reversal phenotype was greatly enhanced ( 97% ). Moreover the anterior expression reverses the polarity of the division even in wild type ( 14% ).These results demostrate that direction of cell polarity is controled by the LIN-44 signal. Although
pop-1/tcf has been shown to be required for asymmetric T cell division, involvement of -catenin has not been shown. We found that
wrm-1/-catenin mutants were defective in the asymmetric T cell division as observed in
lin-17 mutants. This suggests that the asymmetric cell division is controled by -catenin in the canonical Wnt pathway.