Differential IRF8 Transcription Factor Requirement Defines Two Pathways of Dendritic Cell Development in Humans

Urszula Cytlak,Anastasia Resteu,Sarah Pagan,Kile Green,Paul Milne,Sheetal Maisuria,David Mcdonald,Gillian Hulme,Andrew Filby,Benjamin Carpenter,Rachel Queen,Sophie Hambleton,Rosie Hague,Hana Lango Allen,James E.D Thaventhiran,Gina Doody,Matthew Collin,Venetia Bigley

doi:10.1016/j.immuni.2020.07.003

Abstract

SummaryThe formation of mammalian dendritic cells (DCs) is controlled by multiple hematopoietic transcription factors, including IRF8. Loss of IRF8 exerts a differential effect on DC subsets, including plasmacytoid DCs (pDCs) and the classical DC lineages cDC1 and cDC2. In humans, cDC2-related subsets have been described including AXL+SIGLEC6+ pre-DC, DC2 and DC3. The origin of this heterogeneity is unknown. Using high-dimensional analysis, in vitro differentiation, and an allelic series of human IRF8 deficiency, we demonstrated that cDC2 (CD1c+DC) heterogeneity originates from two distinct pathways of development. The lymphoid-primed IRF8hi pathway, marked by CD123 and BTLA, carried pDC, cDC1, and DC2 trajectories, while the common myeloid IRF8lo pathway, expressing SIRPA, formed DC3s and monocytes. We traced distinct trajectories through the granulocyte-macrophage progenitor (GMP) compartment showing that AXL+SIGLEC6+ pre-DCs mapped exclusively to the DC2 pathway. In keeping with their lower requirement for IRF8, DC3s expand to replace DC2s in human partial IRF8 deficiency.

Highlights

The hematopoiesis of dendritic cells (DCs) is controlled by a network of transcription factors (TFs), including GATA2, SPI1 (PU.1), TCF4 (E2-2), ZEB2, IRF4, IRF8, and IKZF1 (IKAROS) (Murphy et al, 2016; Collin and Bigley, 2018)
CD14 and CD5 expression marked the poles of a phenotypic continuum and CD163+BTLAÀ and CD163ÀBTLA+ populations were identifiable within the CD14ÀCD5À gate
CD14 expression on CD14+CD1c+ DCs is at least 1 log lower than on classical monocytes (Figure S1B), which were excluded by CD88 expression

Summary

Introduction

The hematopoiesis of dendritic cells (DCs) is controlled by a network of transcription factors (TFs), including GATA2, SPI1 (PU.1), TCF4 (E2-2), ZEB2, IRF4, IRF8, and IKZF1 (IKAROS) (Murphy et al, 2016; Collin and Bigley, 2018). Critical roles have been demonstrated in humans for GATA2 (Dickinson et al, 2014), IRF8 (Hambleton et al, 2011; Bigley et al, 2018), and IKZF1 (Cytlak et al, 2018). Single-cell cloning experiments demonstrate oligo- and unipotent differentiation pathways and highlight critical interactions between TFs such as SPI1 (PU.1) and IRF8 in priming and directing DC development (Lee et al, 2017; Velten et al, 2017; Giladi et al, 2018).

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Conclusion