Differential expression of A microRNA in the development of dendritic cells

Abstract

Dendritic cells (DCs) are professional antigen-presenting cells that sample and present antigens to naïve T lymphocytes, which is necessary for the subsequent antigen-specific T-cell immune responses. DCs exist in a range of distinct subpopulations including plasmacytoid DCs (pDCs) and classical DCs (cDCs), with the latter consisting of the cDC1 and cDC2 lineages. Although the roles of DC-specific transcription factors across the DC subsets have become understood, the posttranscriptional mechanisms that regulate DC development are yet to be elucidated. MicroRNAs (miRNAs) are pivotal posttranscriptional regulators of gene expression in a myriad of biological processes, but their contribution to the immune system is just beginning to surface. To identify miRNAs possibly involved in DC development and function, we screened for the expression of candidate miRNAs that target the 3’UTR of relevant transcriptional factors from our in-house probe collection. We identified miR-124 which was able to target and directly regulate the expression of transcription factor Tcf4, a gene known to be critical for the development and homeostasis of pDCs. We then utilized an in vitro model for DC development using bone marrow (BM) culture with Flt3L, where miR-124 was exceedingly expressed in pre-cDCs relative to the mature DC subsets (pDC, cDC1, and cDC2). Meanwhile, the in vivo expression profiling of the subsets isolated from BM showed that miR-124 was outstandingly expressed in CD24+ cDC1s compared to DC precursors, pDCs, and CD172α+ cDC2s. We also investigated the effects of miR-124 mimic or inhibitor exaggeration on DC development to examine the phenotypic changes influenced by miR-124. Transfection of miR-124 mimic into BM common DC progenitors (CDP) followed by culture with Flt3L caused significant changes in resulting mature DC populations, where large decrease of a previously unrecognized DC subset was observed. These results imply mechanistic involvement of miR-124 in DC subset differentiation. These insights will provide further evidence into understanding a sophisticated process to regulate DC ontogeny where miR-124 plays a crucial role in DC development and function.