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 intestine from cecum to distal colon. A low level of mRNA expression was detected in the liver, but no other tissues analyzed expressed the transgene. In 2022, the investigator reported that ~3-22 copies of the transgene are integrated on chromosome 8 (85,597,602-85,597,668 [GRCm38]) and resulted in a 64bp deletion of genomic region in between the two identified breakpoints. There are no genes annotated in this region [NCBI genome browser - GRCm38 - Chr8:85,597,400-85,597,800].
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