When organoids from Hmga1 mice were incubated with Wnt3a to enhance lentiviral transduction, we observed a striking phenotype whereby the Hmga1 organoids formed very large, cyst-like, spherical organoids comprised predominantly of Lgr5+ ISCs, in contrast to WT organoids, which generated smaller cysts at a decreased frequency (Fig. 4a; Supplementary Fig. 6). The gene discussed is WNT3A; the disease is cyst.