In order to validate and quantify the BAT-gal reporter expression changes in the Pygo2 null and Pygo1/Pygo2 nulls, we performed ELISA measurements of transgene specific β-galactosidase levels in E18.5 kidneys (Figure 7). Loss of the Pygo2 gene (Pygo1+/-/Pygo2-/- and Pygo1-/-/Pygo2-/-) gave greater than 90% reduction in BAT-gal expression. Loss of Pygo1 alone (Pygo1-/-/Pygo2+/+) did not result in a significant change. Interestingly, however, the Pygo1-/-/Pygo2+/- showed only 50% of wild-type BAT-gal expression, suggesting a minor contribution by Pygo1 in canonical Wnt signaling. Although BAT-gal expression was decreased in the E18.5 Pygo1-/-/Pygo2+/- kidney, confocal analysis of kidneys with this genotype revealed no dilated ureteric tips or significant changes in ureteric tip number per area compared with Pygo1-/-/Pygo2+/+ kidneys (data not shown). Collectively, these BAT-gal reporter results suggest a significant role for the Pygo1 and Pygo2 genes in canonical Wnt signaling during development of the ureteric tree of the kidney.