# Systematic monocyte subset analysis reveals differential contribution of Notch signaling components to monocyte heterogeneity

## TL;DR

This study shows how different parts of the Notch signaling pathway affect the diversity and behavior of monocyte subsets in the immune system.

## Contribution

The study reveals differential roles of Notch2 and Rbpj in regulating monocyte subset development and plasticity.

## Key findings

- Notch2 broadly affects Ly6Clo monocyte development and phenotypes.
- Rbpj deletion has more restricted effects, mainly on monocyte phenotypes.
- DLL1/4-Notch2 regulates plasticity of GC-like monocytes toward other subsets.

## Abstract

Monocyte heterogeneity and plasticity create a spectrum of phagocytes essential for innate immune functions, which is partially regulated by Notch signaling. Using systematic monocyte subset analysis in different compartments, we here confirm that monocyte heterogeneity extends beyond the Ly6Chi and Ly6Clo monocytes and is regulated by Notch. Employing different monocyte-lineage-development-specific Cre-deleter strains in combination with conditional alleles for the receptor Notch2 or the Notch nuclear mediator Rbpj, we also show that subset development is differentially regulated by Notch-signaling components. Deletion of Notch2 broadly affects development of Ly6Clo monocytes, or related monocyte subsets, and alters monocyte phenotypes, while deletion of Rbpj has more restricted effects, mostly on monocyte phenotypes. Furthermore, the developmental plasticity of Ly6Chi monocyte subsets in vitro is regulated by Notch2 but dependent on the context of specific Notch ligand and myeloid growth factor. Thus, Notch signaling components differentially regulate monocyte heterogeneity and plasticity.

•Notch2 controls monocyte conversion and phenotype and defines heterogeneity of monocyte pools•Rbpj regulates monocyte phenotype and migration, contributing to monocyte heterogeneity•DLL1/4-Notch2 controls conversion of DC/GC-like monocytes in a growth-factor-dependent manner•DLL1/4-Notch2 regulates GC-like monocyte plasticity toward monocyte subsets and MoDCs

Notch2 controls monocyte conversion and phenotype and defines heterogeneity of monocyte pools

Rbpj regulates monocyte phenotype and migration, contributing to monocyte heterogeneity

DLL1/4-Notch2 controls conversion of DC/GC-like monocytes in a growth-factor-dependent manner

DLL1/4-Notch2 regulates GC-like monocyte plasticity toward monocyte subsets and MoDCs

Molecular biology; Immunology; Cell biolog