Heterotaxin: A TGF-β Signaling Inhibitor Identified in a Multi-Phenotype Profiling Screen in Xenopus Embryos

Disruptions of anatomical left-right asymmetry result in life-threatening heterotaxic birth defects in vital organs. We performed a small molecule screen for left-right asymmetry phenotypes in Xenopus embryos and discovered a pyridine analog, heterotaxin, which disrupts both cardiovascular and digestive organ laterality and inhibits TGF-β-dependent left-right asymmetric gene expression. Heterotaxin analogs also perturb vascular development, melanogenesis, cell migration, and adhesion, and indirectly inhibit the phosphorylation of an intracellular mediator of TGF-β signaling. This combined phenotypic profile identifies these compounds as a class of TGF-β signaling inhibitors. Notably, heterotaxin analogs also possess highly desirable antitumor properties, inhibiting epithelial-mesenchymal transition, angiogenesis, and tumor cell proliferation in mammalian systems. Our results suggest that assessing multiple organ, tissue, cellular, and molecular parameters in a whole organism context is a valuable strategy for identifying the mechanism of action of bioactive compounds. [Display omitted] ► 2,4,6-substituted pyridines disrupt left-right asymmetry in Xenopus embryos ► Pyridine compounds induce multiple TGFβ-dependent organ and cellular phenotypes ► Pyridine compounds inhibit both Smad2- and non-Smad-dependent TGFβ-signaling events ► Pyridine compounds inhibit EMT, angiogenesis, and mammalian tumor cell proliferation