Figure 5. ERK1/2 signalling is required for Erk5^−/− intestinal organoid growth.

Intestinal organoids were generated from Erk5^fl/fl mice and transduced with Cre^ERT2 pMSCV retrovirus. Organoids were then treated with EtOH or 4-hydroxytamoxifen (0.5 μM), together with DMSO or PD0325901 (100 nM) for 2 days. Organoids were analysed on day 5 of culture and imaged by confocal microscopy after immunofluorescent staining for Ki67 and F-actin (a). Morphology of EtOH or tamoxifen treated Erk5^fl/fl organoids after transduction with Cre^ERT2 retrovirus, with or without co-treatment with PD0325901, visualized by live-cell brightfield microscopy (b). Analysis of Erk5 (c), and Mki67 (d) transcript levels in organoids after treatment, measured by Q-PCR and normalized to 18 S rRNA (n=2–3 per group). Data are mean±s.e.m. *P<0.05, **P<0.01 versus control (EtOH) or as indicated, by analysis of variance. Data are representative of at least two experiments. Scale bars, 100 μm (a and b).