Human and mouse ABCA1 comparative sequencing and transgenesis studies revealing novel regulatory sequences

The expression of ABCA1, a major participant in apolipoprotein-mediated cholesterol efflux, is regulated by a variety of factors, including intracellular cholesterol concentration. To identify sequences involved in its regulation, we sequenced and compared approximately 200 kb of mouse and human DNA containing the ABCA1 gene. Furthermore, expression of the human gene containing different 5' ends was examined in transgenic mice. Sequence comparison revealed multiple conserved noncoding sequences. The two most highly conserved noncoding elements (CNS1, 88% identity over 498 bp; CNS2, 81% identity over 214 bp) were also highly conserved in other organisms. Mice containing the human ABCA1 gene, 70 kb of upstream DNA, and 35 kb of downstream DNA expressed the transgene similarly to endogenous Abca1. A second transgene beginning 3' to exon 1 was expressed only in liver, providing strong evidence of an unsuspected liver-specific promoter. The identified conserved noncoding sequences invite further investigation to elucidate ABCA1 regulation.