TBX18 is a T-box transcription factor that functions as a transcriptional repressor essential for the development of multiple organ systems. In cardiovascular development, TBX18 is expressed in smooth muscle cells of the aorta and is critical for normal aortic development and homeostasis 1. Embryonic conditional ablation of Tbx18 results in severe aortic malformations and lethality, while adult ablation causes milder phenotypes but exacerbates aortic dysfunction when combined with Marfan syndrome mutations 1. TBX18 also plays a crucial role in cardiac pacemaker function, as myocardial injection of TBX18 mRNA can generate de novo cardiac pacing in animal models of complete heart block 2. In urogenital development, TBX18 is essential for ureteral development, with induced ureteral stromal progenitors from pluripotent stem cells requiring functional TBX18 for proper development 3. The protein functions through direct DNA binding to regulate target genes, including immediate early genes like EGR1, FOS, and JUNB 1. Disease associations include congenital heart defects, where variants in the TBX18 promoter region significantly decrease transcriptional activity and are found in patients with ventricular septal defects 4, and congenital anomalies of kidney and urinary tract.