Cre/lox recombination in the lower urinary tract.

Tbx18 is a T-Box transcription factor that has specific expression and indispensible function in the lower urinary tract. Here, we report the generation and characterization of a bacterial artificial chromosome (BAC) transgene expressing Cre under the control of Tbx18 regulatory elements. When crossed to the ROSA26R-lacZ reporter mice, the Tbx18-Cre transgene mediates loxP recombination in the mesenchymal derivatives in the lower urinary tract, especially in the smooth muscle cells (SMCs) and the stromal cells. There is no expression of this transgene in the urothelium or in the kidney. This Tbx18-Cre transgene recapitulates the endogenous Tbx18 expression in the urinary system and can be used for the study of the development, physiology, and diseases in the urinary tract. Its additional expression in the epicardium, limb, vibrissae, and other structures would be useful for studies in the relevant fields.