DEVELOPMENTAL REGULATION OF THE MURINE β‐GLOBIN LOCUS

Abstract

The mouse β‐globin locus contains four genes sequentially expressed during development—εy and βH1 in the embryo and βmaj and βmin in the adult—under the influence of an upstream locus control region (LCR). 3C experiments have shown that the adult β‐globin genes establish proximity with the LCR to effect gene activation, but whether this is the case for the embryonic genes, which are closer to the LCR, is unclear. Using a knock‐in approach, we targeted a copy of the chicken β‐globin HS4 insulator between the LCR and εy, the closest downstream gene. Imposition of the insulator decreased recruitment of transcription activators and RNA pol II to εy and βH1 and repressed their expression. Instead, RNA pol II accumulated at the insulator accompanied by increased intergenic transcription. This result suggests that the insulator interrupts pol II tracking or spreading from the LCR to the downstream embryonic genes. We are breeding mice with this insertion to test its function during development. In addition, we are targeting HS4 to a position between the embryonic and adult globin genes. These experiments should provide insight into mechanisms underlying LCR/globin gene communication during development.