Figure 1. Wasting disease associated with malabsorption in Erk1/2^ΔIEC mice.

(a) Immunofluorescent staining of paraffin-embedded sections from small intestine or colon taken from Erk1^−/−;Erk2^fl/fl (‘fl/fl') and Erk1^−/−;Erk2^fl/fl;Vil-Cre^ERT2 (‘ΔIEC') mice for an IEC marker, Claudin-1 (green) and ERK1/2 (red). Nuclear counter staining with Hoechst (blue). (b) Body weight changes of fl/fl and ΔIEC mice (n=6 per group) after five consecutive treatments with tamoxifen (1 mg day⁻¹). *P<0.05, **P<0.001 by analysis of variance. (c) Survival of fl/fl (n=10) and ΔIEC mice (n=9) after tamoxifen treatment (Kaplan–Meier). (d) Macroscopic appearance of the small intestine and abdominal fat pads (indicated by arrows) in fl/fl and ΔIEC mice on day 10 of follow-up. Arrowheads indicate intestinal distension. (e) Weight of the epididymal fat of fl/fl and ΔIEC mice (n=6 per group) at day 10 of follow-up. (f–h) Analysis of serum samples from fl/fl and ΔIEC mice. Albumin and globulin levels (f), glucose levels (g) and calcium levels (h) are shown. (i) Crypt and villus architecture in the small intestine of fl/fl and ΔIEC mice. Lymphangiectasia marked by (*) was only observed in ΔIEC mice. Haematoxylin and eosin (H&E) staining. (j) Alkaline phosphatase (AP) staining of ileum sections from fl/fl and ΔIEC mice. Arrowheads indicate the crypt–villus junction. (k) Transmission electron microscopy (TEM) analysis of the brush border of absorptive enterocytes at × 25,000 magnification. Data are presented as mean±s.e.m. (b), box-and-whiskers plots (e) or scatter plots with mean (f–h). *P<0.05 and **P<0.001 by Student's t-test (e–h). Scale bars, 1 cm (d), 100 μm (i and j), 50 μm (a) or 0.5 μm (k).