Our studies in the past years have been focused on understanding the molecular mechanisms that control cell differentiation and proliferation during development and transformation. Every day it is more accepted that both processes share similar mechanism of regulation at the transcription and signal transduction levels. A paradigm for studying these processes are the organs derived from the endoderm, as development and cancer can be well studied using different animal models and cell systems. We have focused our investigation on the thyroid gland, an organ derived from the endoderm that is responsible for thyroid hormone biosynthesis. This organ model is well suited for studying embryonic development and mechanisms involved in differentiation and proliferation. We believe that understanding these processes is by no means solely academic, since identification of the inductive molecules involved
in thyroid development and thyroid proliferation and differentiation will likely provide clues to novel pathogenetic mechanisms of thyroid disorders in human.