In situ hybridization has been used previously to characterize expression of Pygo1 [14,16](Yu J, Valerius MT, McMahon AP, contribution to GUDMAP, ). In this report, we used immunofluorescence to better define the expression patterns of the Pygo1 and Pygo2 genes in the developing kidney. Both genes were widely expressed, showing nuclear localization of encoded proteins in the ureteric bud, capping mesenchyme, and stromal cells (Figure 2). Raised expression of Pygo1, and to a lesser degree of Pygo2, was seen in stromal cells, and significant nuclear staining was detected in essentially all cells of the developing kidney for both proteins.