Fig. 6

Knocking out of TRβ tadpoles reduces intestinal stem cell proliferation during T3-induced metamorphosis. A Reduced EdU labeling in TRβ knockout tadpoles after T3 treatment. Wild type (a–j) and TRβ knockout (k–t) tadpoles at stage 54 were treated with or without 5 nM T3 treatment for up to 5 days. The animals were injected with EdU solution for 30 min before being sacrificed. Cross-sections of the intestine were prepared and stained with Hoechst 33342 for DNA and EdU for proliferating cells. The dotted lines depict the epithelium-mesenchyme boundary, drawn based on morphological differences between epithelial cells and mesenchyme cells in the pictures of the stained tissues, under enhanced contrast and/or brightness by using Photoshop, if needed. Dashed yellow boxes (f, h, p and r) indicate the higher magnification (i, j, s and t), respectively. EdU: red, and Hoechst: blue. T: typhlosole. At least 3 tadpoles were analyzed for each genotype. Bars: 100 µm. B EdU positive area was reduced in the intestine of TRβ homozygous knockout animals. The EdU positive area in A was quantified and normalized against the Hoechst 33342 positive area. Different lower case letters denote statistically significant differences (P < 0.05) when compared in a single genotype and asterisks (***) indicate a significant difference between the two genotypes (P < 0.001). ns no significant difference