FIG. 6.

TRα knockout causes reduction in mmp expression during intestinal remodeling. (A) Mapping of TRα-specific T3-regulated genes to the ECM–receptor interaction pathway (KEGG). Genes regulated by T3 for at least twofold after one day of T3 treatment of wild-type but not TRα^−/− tadpole were mapped onto the KEGG pathway for the ECM–receptor interaction. Pink boxes indicate upregulation, and blue boxes indicate downregulation. Note that all mapped genes were upregulated by T3. (B) The mRNA level of mmp genes in the intestine is significantly increased during T3-induced metamorphosis in wild-type tadpoles but not in TRα^−/− tadpoles. The mRNA levels of mmp2, mmp9, mmp11, mmp13, and mmp14 were determined by real-time PCR and shown relative to the levels in the wild-type intestine at stage 54. The wild-type intestine had much higher levels of expression of mmp2, mmp9, mmp11, mmp13, and mmp14 after one and two days of T3 treatment. The asterisk (*) indicates a significant difference between the TRα^−/− tadpoles and wild-type tadpoles (p < 0.05). Experiment was repeated twice, and each bar represents the mean + S.E. ECM, extracellular matrix.