Proper developmental control of human globin genes reproduced by transgenic mice containing a 160-kb BAC carrying the human beta-globin locus

Four independent bacterial artificial chromosome (BAC) clones containing th e human beta -globin gene locus were obtained from a human genomic BAC libr ary. A 160-kb clone (186D7), carrying the entire human beta -globin locus i ncluding the beta -globin gene family, locus control region (LCR), and 3' r egulatory elements was used to transform mice. Four transgenic lines were g enerated by microinjecting the purified BAC DNA into the fertilized eggs. R Nase protection analysis showed that the expression of human beta -globin g enes is tissue- and developmental stage-specific and the expression level i s similar among the three independent transgenic lines which carry the enti re human beta -globin locus; however, no beta -globin gene expression was d etected in the transgenic mice lacking the LCR region. The results suggest that the transgenic mouse model system that we have produced and that uses BAC to study the complex human beta -globin gene cluster is stable and repr oducible. Our results also indicate that some newly characterized HSs upstr eam from the LCR appear not to play an important role in globin gene expres sion and switching, while the traditional LCR can ensure correct human beta -globin gene expression in transgenic mice. The BAC-mediated transgenic sy stem can be used for further studies to determine which kinds of cis-acting elements are included in regulating the developmental timing and the level of human beta -globin gene expression. (C) 2000 Academic Press.