FIG. 4.

SRC3 knockout inhibits T3-induced limb development and intestinal remodeling. (A) SRC knockout inhibits T3-induced limb metamorphosis. WT and SRC3 knockout (SRC3^−/−) tadpoles at stage 54 were treated with 10 nM T3 for three days at 25°C, and the hindlimb region was photographed. The lower panels were the same as the top panels, except with the added white line marking the approximate boundary of the outer limb epithelium and/or the boundaries of the digits (white arrowheads indicate some of the digits of the WT animal treated with T3). Note that limb development (digit formation) is the earliest and most dramatic early event in the WT animals treated with T3. Quantitative analysis revealed that the T3-induced gill resorption was also inhibited in the knockout tadpoles (Supplementary Fig. S4). (B) T3-induced intestinal shortening is reduced in the knockout tadpoles. The length of the intestine in WT and SRC3^−/− tadpoles as in (A) was measured and normalized against body length. Error bars indicate SEM. *p < 0.05. (C) Adult epithelium development is inhibited by SRC3 knockout. Cross-sections of the intestine in WT and SRC3^−/− tadpoles as in (A) were stained with methyl green-pyronin Y (staining DNA blue and RNA red). Note that the adult epithelium folds were formed after three days of T3 treatment only in WT but not SRC3^−/− tadpoles.