DEVELOPMENTAL BIOLOGY Creating Asymmetry

Abstract:

Whangbo, Harris, and Kenyon investigated the role of EGL-20 (a nematode Wnt molecule) in the asymmetric cell divisions of specific lateral epidermal cells (V5), which exhibit an anterior/posterior polarity on division, leading to two different cell fates: epidermal syncytium or seam cell, respectively. In egl-20 mutant worms, V5 divides asymmetrically, but there is a reversal of the polarity of the V5 cell daughters, such that the anterior cell differentiates into a seam cell, and the posterior cell becomes part of the epidermal syncytium. Using genetic analysis, they determined that EGL-20 does not act through a classical Wnt pathway that involves LIN-17 (a Wnt receptor), BAR-1, MIG-1, and MIG-14. Furthermore, introduction of a lin-17 mutation into the egl-20 mutant suppresses the reversed polarity seen in the egl-20 mutants, suggesting that LIN-17 acts in the pathway that leads to the polarity reversal. Additionally, EGL-20 appears to counter a signal produced by neighboring posterior cells, because the reversed polarity in egl-20 mutants is eliminated if the two adjacent posterior cells are ablated. Thus, many layers of signaling exist that dictate asymmetric cell divisions and anterior/posterior polarity.

Whangbo, J., Harris, J., and Kenyon, C. (2000) Multiple levels of regulation specify the polarity of an asymmetric cell division in C. elegans. Development 127: 4587-4598. [Online Journal]