Good question which I can't answer. However, if you are screening by qPCR, make sure the primers for RSpondin 1,2,3 are good. See Kabiri Z from Virshup DM (Stroma provides an intestinal stem cell niche in the absence of epithelial Wnts. Development 2014, 141:2206-2215, doi: 10.1242/dev.104976