Defining Wnt activity and Nkd1 function in mammalian cell lines IEC-18 and HEK293
Wnt signaling is an evolutionarily conserved pathway involved in many aspects of development and stem cell homeostasis. Activating mutations within the Wnt pathway are key in the initiation of colorectal cancers. Nkd1 is a negative feedback regulator of Wnt signaling with a unique method of antagonism that could potentially block the effect of the activating mutations. However, our understanding of the molecular function of Nkd1 has been derived mainly through zebrafish studies. To ultimately better understand the role of Nkd1 in human disease, I first employed the Intestinal Epithelial Cells line 18 (IEC-18) and Human Embryonic Kidney cells (HEK293) as mammalian models for the investigation of Nkd1 function. Using these two cell lines, I characterized the biochemical and genetic status of Wnt signaling in IEC-18 and HEK293 cells, followed by an analysis of Nkd1 function as it relates to previous work performed in zebrafish. My results indicate that while both cells respond biochemically and genetically to Wnt signaling, there are significant differences in the level of response at both levels that are not congruent with the current dogma. In addition, I found that while Nkd1 activity in these mammalian cell types shares some similarities with our previous findings in zebrafish, there exists cell-dependent differences in Nkd1 function.