The transgene is composed of the cre recombinase gene under the control of a composite promoter derived from rat Pbsn. The rat Pbsn promoter drives postnatal transgene expression in the prostatic epithelium. The transgene is expressed postnatally in prostatic epithelium with the highest level of expression in the lateral lobe of the prostate gland. A very low level of transgene expression was detected in the seminal vesicles, testes, and ovaries. No transgene expression was detected in any of the other tissue types examined.