Small-molecule triggers of tadpole metamorphosis.

Small molecules that function as highly selective agonists and antagonists of cellular receptors comprise some of the most valuable therapeutic agents and molecular probes. A recent paper describes the design, synthesis, and evaluation of CO23, the first potent and specific agonist of thyroid hormone receptor-alpha (TRalpha), a member of the nuclear receptor (NR) superfamily of transcription factors. Together with previously reported TRbeta-selective agonists such as GC-1, these compounds represent powerful new tools for studying gene expression, signaling, differentiation, and development controlled by this important NR.