TBXT (T-box transcription factor T) is a critical transcription factor that regulates mesoderm formation and early embryonic development. TBXT binds to palindromic T-site DNA sequences (5'-TTCACACCTAGGTGTGAA-3') and activates transcription of genes required for mesodermal differentiation 1. During gastrulation, TBXT expression initiates at the primitive streak and its dosage must be precisely regulated to ensure proper cell fate specification and anterior-posterior axis patterning 1. TBXT plays essential roles in notochord formation, with conserved enhancers controlling its cell-type-specific expression through auto-regulatory mechanisms 2. In nascent mesoderm, TBXT dosage directly influences the temporal progression of epithelial-to-mesenchymal transition (EMT) and persistence of cell-cell adhesions, though mesodermal identity can be acquired independently of complete EMT 3. TBXT is expressed in notochordal and nucleus pulposus cells during intervertebral disc formation, where it functions in extracellular matrix homeostasis 4. Pathologically, TBXT alterations associate with multiple congenital conditions: an evolutionary Alu-element insertion affecting TBXT splicing in hominoids correlates with tail-loss but increases neural tube defect susceptibility 5. Disease-associated variants in TBXT have been identified in patients with sacral agenesis and vertebral anomalies 6.