A Binary Cre Transgenic Approach Dissects Microglia and CNS Border-Associated Macrophages

•The brain harbors distinct parenchymal and perivascular macrophages.•Binary split Cre transgenesis allows differential imaging translatome retrieval.•Cx3cr1ccre: Sall1ncre mice specifically target microglia.•Cx3cr1ccre: Lyve1ncre a subset of macrophages. The developmental molecular heterogeneity tissue macrophages is unravelling, as are their diverse contributions to physiology pathophysiology. Moreover, also given tissues harbor in discrete anatomic locations. Functional specific cell populations can be dissected using recombinase-mediated mutagenesis. However, single promoter-based models show limited specificity for types. Focusing on the brain, we establish here binary transgenic system involving complementation-competent NCre CCre fragments whose expression driven by promoters: Sall1ncre: Cx3cr1ccre microglia compound Lyve1ncre: animals vasculature-associated macrophages, well other tissues. 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Hawrylycz Jones high-throughput reporting characterization whole brain.Nat. 133-140Crossref (3267) Flow cytometric resulting Tomato+ CX/Sall1 brains largely CD11b+ CD45int, consistent being 1C). rare CX/Lyve1 CD45hi accordance phenotype 1D). Ramified amoeboid morphologies detected microscopy supported conclusion 1E 1F). Ccre-only did (data shown). cytometry quantification heterozygote Sall1ncre/wt: Cx3cr1ccre/wt: R26-tdTomato about quarter identified SiglecH Tmem119 staining, S2A). Rearrangement efficiency considerably increased Sall1ncre/ ncre: Cx3cr1ccre/ ccre alleles modified 1G, 2A, 2 B). Notably, confirming retention allele, ncre signs activation, Sall1-deficient 1H) Lyve1ncre/wt: around 5% CD206+ S2B). Notably though, retrieval flow affected protocol dissociation improved inclusion hyaluronidase collagenase type I Papain S2C). More reliable, histological instance 20% S2D S2F). Again, abundance threefold Lyve1ncre/ mice, S2E Histological parenchyma overlaying, highly vascularized corroborated / bearing exclusively underlying vasculature characteristic ramified morphology 2C). absent dura (Fig