Proper Developmental Control of Human Globin Genes Reproduced by Transgenic Mice Containing a 160-kb BAC Carrying the Human β-Globin Locus

Abstract

ABSTRACTFour independent bacterial artificial chromosome (BAC) clones containing the human B-globin gene locus were obtained from a human genomic BAC library. A 160-kb clone (186D7) carrying the entire human B-globin locus including the B-globin gene family, locus control region (LCR), and 3′ regulatory elements was used to transform mice. Four transgenic lines were generated by microinjecting the purified BAC DNA into the fertilized eggs. RNase protection analysis showed that the expression of human B-globin genes is tissue- and developmental stage-specific and the expression level is similar among the three independent transgenic lines which carry the entire human B-globin locus; however, no B-globin gene expression was detected 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 B-globin gene cluster is stable and reproducible. Our results also indicate that some newly characterized HSs upstream from the LCR appear not to play an important role in globin gene expression and switching, while the traditional LCR can ensure correct human B-globin gene expression in transgenic mice. The BAC-mediated transgenic system 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 B-globin gene expression.