Molecular and genetic studies on the signaling and the regulation of amphibian metamorphosis by thyroid hormone, the contribution of Jamshed Tata and Donald Brown

Post-embryonic development refers to the process by which embryonic development has been completed and the organism reaches maturation. Amphibian metamorphosis represents one of the most extreme examples of post-embryonic transition. In Anuran frogs, embryonic development ends at a tadpole stage, which corresponds to the larval form of the animal. Ultimately, the juvenile frog stage is reached after a period of growth. The complex changes corresponding to this dramatic transition are so profound they have been termed meta-morphosis, based on the Greek terms for change/after and body. The tissue remodeling transcriptional programs are coordinated at the organism level by the complex interplay between numerous hormones, of which thyroid hormones are the initiator and main contributors. Two ground-breaking biologists have made major contributions to the understanding of the molecular processes underlying amphibian metamorphosis. Jamshed R. Tata (1930-2020) was an Indian-born British endocrinologist who established that thyroid hormones act by regulating gene expression. Donald D. Brown (1931-2023) was an American biologist and one of the founders of molecular embryology. Both recognized the exceptional potential of amphibian metamorphosis as a model for understanding thyroid hormone function and mechanisms of action, as well as the fundamental principles governing post-embryonic development.