Two differentiation pathways generate large peritoneal macrophages with one replenishing mesothelial border...

Area of Science:

• Immunology
• Cell Biology
• Developmental Biology

Background:

• The peritoneal cavity harbors distinct resident macrophage populations, including large cavity macrophages (LCMs).
• LCMs are characterized by Gata6 expression and reside on mesothelial surfaces and in peritoneal fluid.

Purpose of the Study:

• To elucidate the distinct differentiation pathways giving rise to LCMs.
• To investigate the roles of transcription factors Gata6 and Zeb2 in LCM development.
• To understand the functional divergence of LCM subsets.

Main Methods:

• Analysis of LCM development in wild-type and mutant mice (Zeb2 enhancer mutations).
• Monocyte differentiation assays.
• Adoptive transfer of macrophage intermediates.
• Assessment of macrophage surveillance and replenishment functions.

Main Results:

• Two separable differentiation pathways for LCMs were identified.
• A minor pathway involves monocytes, is Zeb2-dependent, and generates LYVE1+ LCMs.
• A dominant pathway is Gata6-dependent, generates Gata6+ LCMs, and is independent of the Zeb2 enhancer mutations.
• The minor pathway macrophages surveil the mesothelium and replenish border macrophages.

Conclusions:

• LCMs arise from two distinct developmental routes with differential reliance on Gata6 and Zeb2.
• These pathways lead to LCMs with unique phenotypes and functional specializations.
• Findings challenge simple embryonic vs. adult hematopoietic paradigms for resident macrophage origins.