Almost all cells exhibit some form of polarity. Interestingly, the mechanisms and even the molecules involved in the control of polarity are often conserved. While the molecules involved are often conserved, their regulatory relationships can sometimes be diverged, which can only be discerned from functional studies. We are interested in the functional conservation of several key genes in a pathway controlling polarity in related nematode species. We have focused our studies on particular asymmetric cell divisions in the C. elegans tail whose polarities are controlled by Wnt signaling. Wnt signaling pathways function in diverse developmental processes in all animals, and have been shown to function in the development of several diseases and forms of cancer. LIN-44/Wnt and LIN-17/Fz are involved in the regulation of T and B cell polarities. The pathway that regulates T cell polarity also includes WRM-1/<font face=symbol>b</font>-catenin, LIT-1/MAPK and POP-1/Tcf, which is asymmetrically distributed to the T cell daughters. Since much is known about the control of T cell polarity in C. elegans, we are now interested in how this mechanism is conserved in the related nematode C. brigssae. Using a simple phasmid dye-filling assay, we were able to confirm that wild-type C. brigssiae animals show normal T cell polarity as the phasmid dye-filling was normal. We are using RNA interference (RNAi) to assess the function of the C. briggsae orthologs of the Wnt pathway involved in the control of cell polarity. Our first target gene was
lin-44, for which the C. brigssiae is CBG12066, or
Cb-lin-44. Knockdown of
Cb-lin-44 caused a phasmid dye-filling defect, indicating a defect in T cell polarity. We also determined that this was caused by a lineage defect. We will continue our analysis of
Cb-lin-44 and begin analysis of the other orthologs in the Wnt pathway in C. brigssiae. Analysis of other conserved developmental pathways between C. elegans and C. brigssiae has shown that in some cases both the orthologs and their regulation is conserved (1), while in others the orthologs are conserved, but their regulation is not (2). Both cases are interesting and have revealed new mechanisms of developmental regulation as well as how developmental regulatory mechanisms evolve. We expect that analysis of the Wnt pathway that controls cell polarity in C. brigssiae will reaveal similar insights. 1. Maduro, M. F., 2006. Bioessays. 28, 1010-22. 2. Haag, E. S., et al. (2005), ed. WormBook, doi/10.1895/wormbook.1.120.1,
http://www.wormbook.org.