cMaf supports Zeb2 expression for primitive hematopoiesis (CUT&RUN)

Microglia arise exclusively from yolk sac (YS) progenitors during primitive hematopoiesis, while other tissue resident macrophages (TRMs)originate during transient-definitive and definitive hematopoiesis. Macrophages require the transcriptional repressor Zeb2 for development, and macrophages developing during definitive hematopoiesis require the ‒165 kb Zeb2 enhancer. However, microglia develop normally in Zeb2 ‒165kb mice lacking this enhancer, indicating that a distinct genetic program supports macrophage development in primitive hematopoiesis. Here, we identify the molecular basis that distinguishes macrophage development in primitive vs. definitive hematopoiesis. We show that all tissue resident macrophages (TRMs) that develop in Zeb2 ‒165kb mice arise exclusively during primitive hematopoiesis, showing that even erythro-myeloid progenitors (EMPs) from the transient-definitive stage rely on the ‒165 Zeb2 enhancer. Next, we identified the transcription factors Maf and Jun as being expressed by yolk sac (YS) progenitors during primitive hematopoiesis, but not by progenitors during definitive hematopoiesis. Further, we find that Maf and Jun together induce Zeb2 expression independently of the ‒165 kb Zeb2 enhancer and restore macrophage development from adult bone marrow progenitors in Zeb2 ‒165kb mice. Finally, Maf-deficient embryos show severe ablation of microglia development, confirming the in vivo requirement for Maf in supporting Zeb2 during primitive hematopoiesis. These results illustrate distinct transcriptional pathways controlling macrophage development during primitive and subsequent waves of hematopoiesis.