Monocytes undergo multi-step differentiation in mice during oral infection by Toxoplasma gondii

Aurélie Detavernier,Marion Splittgerber,Muriel Nguyen,Guillaume Oldenhove,Laurye Van Maele,Younes Achouri,Hussein Shehade,François Fuks,David Svec,Stanislas Goriely,Séverine Thomas,Emilie Calonne,Abdulkader Azouz

doi:10.1038/s42003-019-0718-6

Abstract

Monocytes play a major role in the defense against pathogens. They are rapidly mobilized to inflamed sites where they exert both proinflammatory and regulatory effector functions. It is still poorly understood how this dynamic and exceptionally plastic system is controlled at the molecular level. Herein, we evaluated the differentiation process that occurs in Ly6Chi monocytes during oral infection by Toxoplasma gondii. Flow cytometry and single-cell analysis revealed distinct activation status and gene expression profiles in the bone marrow, the spleen and the lamina propria of infected mice. We provide further evidence that acquisition of effector functions, such as the capacity to produce interleukin-27, is accompanied by distinct waves of epigenetic programming, highlighting a role for STAT1/IRF1 in the bone marrow and AP-1/NF-κB in the periphery. This work broadens our understanding of the molecular events that occur in vivo during monocyte differentiation in response to inflammatory cues.

Highlights

Monocytes play a major role in the defense against pathogens
In order to better define the phenotype of these CD11b+Ly6C+ monocytes in these different localizations, we used unbiased clustering t-Distribution Stochastic Neighbor Embedding (t-SNE) multiparameter analysis of Ly6C, CD64, MHCII, CD11c, CD80, CD86, and CD40 staining
We show that at the peak of infection, monocytes acquire distinct phenotypic features according to their localization

Summary

Introduction

Monocytes play a major role in the defense against pathogens. They are rapidly mobilized to inflamed sites where they exert both proinflammatory and regulatory effector functions. Some specific stimulusresponsive transcription factors, such as AP-1, IRF8, or STAT1 may promote the opening of previously inaccessible regions and the acquisition of de novo enhancers that further contribute to cell plasticity[5] Beyond this first degree of specialization imposed by lineage specifications and microenvironmental factors, it is still not clear how the decision to express specific gene patterns is accomplished. Pioneer transcriptomic studies revealed that within an apparently homogeneous population, distinct patterns of gene activation occur at the single-cell level[6] Most of these studies have been conducted under steadystate conditions or on primary macrophages/cell lines cultured in vitro and exposed to a single, well-defined stimulus. We provide evidence that acquisition of effector functions by Ly6Chi monocytes is accompanied by localizationspecific waves of epigenetic programming, dominated by STAT1 in the BM and AP-1/NF-κB in the periphery

Methods

Results

Conclusion