TBX3 (T-Box Transcription Factor 3): TBX3 is a transcription factor that plays a vital role in embryonic development, regulating organ formation including limbs, heart, and mammary glands. Mutations or dysregulation of TBX3 can lead to developmental disorders such as ulnar-mammary syndrome. It is also linked to cancer, where it may function as a transcriptional repressor to inhibit cell ageing and promote cell proliferation.