Chromosome looping at the human alpha-globin locus is mediated via the major upstream regulatory element (HS -40).

Previous studies in the mouse have shown that high levels of alpha-globin gene expression in late erythropoiesis depend on long-range, physical interactions between remote upstream regulatory elements and the globin promoters. Using quantitative chromosome conformation capture (q3C), we have now analyzed all interactions between 4 such elements lying 10 to 50 kb upstream of the human alpha cluster and their interactions with the alpha-globin promoter. All of these elements interact with the alpha-globin gene in an erythroid-specific manner.

Manipulating the mouse genome to engineer precise functional syntenic replacements with human sequence.

We have devised a strategy (called recombinase-mediated genomic replacement, RMGR) to allow the replacement of large segments (>100 kb) of the mouse genome with the equivalent human syntenic region. The technique involves modifying a mouse ES cell chromosome and a human BAC by inserting heterotypic lox sites to flank the proposed exchange interval and then using Cre recombinase to achieve segmental exchange. We have demonstrated the feasibility of this approach by replacing the mouse alpha globin regulatory domain with the human syntenic region and generating homozygous mice that produce only human alpha globin chains.