TBX3 (T-Box Transcription Factor 3): TBX3 is a transcription factor that plays a critical role in embryonic development, regulating organogenesis including limb, heart, and mammary gland formation. Mutations or dysregulation of TBX3 can cause developmental disorders such as ulnar-mammary syndrome. It is also implicated in cancer, where it may act as a transcriptional repressor to inhibit cell senescence and promote cell proliferation.