RUNX1 is essential for definitive haematopoiesis and requires precise regulation for normal development. RUNX1 disruption by mutation or translocation are frequently associated with Acute Myeloid Leukaemia (AML). Despite the well-established role of RUNX1 in haematopoiesis and leukaemogenesis, there is limited knowledge of the cis-regulatory mechanisms that drive cell type-specific RUNX1 expression.
Previously, the +24 Runx1 mouse conserved non-coding element (mCNE) was identified as an enhancer in haematopoietic cells in zebrafish and mice. The Osato research group identified several additional mCNEs in regions surrounding Runx1, which have not yet been tested for functionality.
Circular Chromosome Conformation Capture (4C) identified long range interactions between the Runx1 promoters and putative cis-regulatory elements. This 4C was successfully applied to mouse haematopoietic progenitor (HPC-7) cells and the results provided a clear picture of chromosome conformation information with potential to regulate Runx1 expression. Nine putative enhancers were identified to interact with Runx1-P1 in HPC-7 cells. Two of the nine enhancers had been predicted by the Osato research group.
Zebrafish enhancer assays show that eight of the nine enhancers drive expression in haematopoietic tissue. Since the putative enhancers interact long-range with Runx1, they are likely to have a functional role in regulating Runx1 expression. This research has contributed to the understanding of RUNX1 regulation by cis-regulatory elements, and it will be of future interest to determine if mutation of these elements contributes to AML development.