Gene expression analyses in IRF8-induced monocyte differentiation

To understand the differentiation program in monocyte/macrophage differentiation, we performed ChIP-seq for IRF8 and H3K4me1 together with gene expression profiling during IRF8-induced monocyte differentiation. Both promoter-proximal and -distal binding of IRF8 associated with induction of the genes especially those related to monocytes/macrophages and immunity. DNA motif analysis for cis-regulatory elements of indirect IRF8 target genes predicted KLF4, essential for Ly6C+ monocyte development, to be a downstream transcription factor regulating the indirect target gene expression. Introduction of KLF4 into an Irf8-/- myeloid progenitor cell line induced a subset of IRF8 target genes and partially induced monocyte/macrophage differentiation. Together, this study revealed the genome-wide behavior of IRF8 and the IRF8-KLF4 axis during monocyte differentiation. Gene expressions in monocyte-like cells differentiated by IRF8 or KLF4 were measured at day 4 after retroviral transductions to myeloid progenitor cell line, Tot2. Two independent experiments were performed.