Fig. 4

T3 response genes fail to be upregulated in the intestine of TRβ knockout tadpoles during metamorphosis. Total RNA was isolated from the intestine of wild type and TRβ knockout tadpoles at stage 54 treated with or without 10 nM T3 for 18 h and used for real-time RT-PCR analysis of the expression of TRα and known T3 direct target genes: TRβ, klf9, and TH/bzip; genes related to ECM remodeling: mmp2, mmp9, mmp11, and mmp14; apoptosis-related genes: caspase 3 (casp3) and caspase 9 (casp9); and cell dedifferentiation-related genes: ror2 and wnt5a. The mRNA levels were normalized against that of rpl8. The groups included 5 wild type and 5 TRβ homozygous [TRβ^(−/−)] animals. Note that T3 upregulated the expression of nearly all genes in the wild type animals but this upregulation was drastically reduced or abolished in the knockout animals. Asterisks (*, ** and ***) indicate a significant difference vs wild type as determined by student-t test (P < 0.05, P < 0.01 and P < 0.001). ns no significant difference