Expression Profiles of Novel Thyroid Hormone-Responsive Genes and Proteins in the Tail ofXenopus laevisTadpoles Undergoing Precocious Metamorphosis

Thyroid hormones (THs) are critical for the growth, development, and homeostasis of many organisms and are necessary for metamorphosis of Xenopus laevis tadpoles. TH-induced metamorphosis requires alterations in the transcriptome and the proteome. However, only a few of the molecular components of this developmental program have been identified and their interrelationship remains unclear. Using a cDNA array comprised of 420 known anuran genes and quantitative PCR, we have identified 93 TH-responsive genes in the tail of premetamorphic tadpoles after exogenous administration of T3. Fifty-three of these mRNA transcripts have not previously been characterized as TH responsive in any species. The gene expression profiles show distinctive temporal patterns with most transcript steady-state levels increasing after induction of metamorphosis. Two-dimensional gel electrophoresis of total protein extracts from the tail shows changes in steady-state levels of many proteins after T3 treatment. Of the up-regulated proteins, 10 were identified by peptide mass mapping. These data identify potential components involved in the regulation of Xenopus tail regression by T3 and begin to address a critical question regarding the interrelationship between the transcriptome and the proteome in TH-dependent developmental processes.