Cell to cell transfer of the chromatin-packaged human b-globin gene cluster

Cell type-specific gene expression is regulated by chromatin structure and the transcription factors provided by the cells. In the present study, we introduced genes packaged into chromatin into target cells using a human artificial chromosome (HAC) and analyzed regulation of gene expression. The human b-globin gene cluster was built into an HAC (globin-HAC) and introduced into mouse embryonic stem (ES) cells using microcell-mediated chromosome transfer (MMCT); the adult-type human b-globin gene was expressed in bone marrow and spleen cells of the transgenic mice. In vitro differentiation of ES cells into mouse erythrocytes indicated that the natural sequential expression of e, g and b-globin genes was reproduced on the globin-HAC. Combination of MMCT and a novel chromosome transfection technique allowed transfer of globin-HAC from HT1080 cells into the human leukemia cell line K562, and from K562 cells back into HT1080 cells. Expression of the g-globin gene, repressed in HT1080 cells, was activated in K562 cells without any processes of differentiation into adult erythroid cells, and was completely repressed again in HT1080 cells when transferred back from K562 cells. Thus, transfer of target genes packaged into chromatin using a HAC was useful for functional analyses of gene regulation.