We also observed an increase in Arm staining in progenitor cells (cells with small nuclei) of Mex > Pex5-i, which indicates higher Wnt pathway activation in the mutant compared with control; this is linked to increased progenitor cells and epithelial dysplasia [55] that we previously described in Mex > Pex5-i intestines [36]. Here, PEX5 is linked to intraepithelial neoplasia.