The 10.6 kb colon-specific promoter and the share 2.5 kb erythroid/colon enhancer from the mouse Car1 gene were PCR amplified and cloned in front of the cre recombinase gene in a plasmid vector. The purified construct was used to generated transgenic mice. Two lines were selected for further analysis. Line 5 (CAC5 with 40 copies to the transgene insertion) was shown by PCR to have 10-fold higher transgene mRNA levels than line 6 (CAC6 having 20 copies). The mRNA was detectable only in the large intestinefrom cecum to distal colon. A low level of mRNA expression was detected in the liver, but no other tissues analyzed expressed the transgene.