A Cre-deleter specific for embryo-derived brain macrophages reveals distinct features of microglia and border macrophages

Brioschi, Simone; Peng, Vincent; Molgora, Martina; Rodrigues, Patrick; Nguyen, Khai M.; Wang, Shoutang; Du, Siling; Wang, Wei-Le; Grajales‐Reyes, Gary E.; Ponce, Jennifer M.; Yuede, Carla M.; Li, Qingyun; Baer, John M.; DeNardo, David G.; Gilfillan, Susan; Cella, Marina; Satpathy, Ansuman T.; Colonna, Marco

doi:10.1016/j.immuni.2023.01.028

Cited by 34 publications

(38 citation statements)

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“…To our knowledge, similar activity has not yet been shown for the Cx3cr1-Cre M line and should not be assumed in absence of confirmation studies given available scRNA sequencing data that shows less consistent expression of this gene across several microglia subsets during development (Hammond et al, 2019; Li et al, 2019). Another line that does appear to recombine in these cells has recently been reported, named Crybb1-Cre (Brioschi et al, 2023). However, this line was not publicly available at the time of this study and has hence not been directly examined here.…”

Section: Discussionmentioning

confidence: 99%

“…Currently, several transgenic lines are available for constitutive (Cre) or inducible (CreERT2) deletion of floxed sequences. For Cre lines, loci harnessed include Tie2, Csf1r, Lyz2, Cx3cr1, Cx3cr1/Sall1 (Clausen et al, 1999; Kisanuki et al, 2001 p.2; Ferron and Vacher, 2005; Kim et al, 2006; Samokhvalov et al, 2007; Yona et al, 2013; Orthgiess et al, 2016 p.2) and, more recently, Crybb1 (Brioschi et al, 2023). For CreERT2, the currently most faithful lines target Tmem119, HexB, P2ry12 , or Cx3cr1 (Parkhurst et al, 2013; Yona et al, 2013; Kaiser and Feng, 2019; Masuda et al, 2020; McKinsey et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

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Transgenic Targeting ofFcrlsCreates a Highly Efficient Constitutively Active Microglia Cre Line with Differentiated Specificity

Kaiser,

Dattero,

et al. 2023

Preprint

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Microglia carry out important functions as the resident macrophages of the brain. To study their role in health and disease, the research community needs tools to genetically modify them with maximum completeness in a manner that distinguishes them from closely related cell-types, such as monocytes. While currently available tamoxifen-inducible CreERT2 lines are able to achieve the differentiation from other cells, the field needs improved and publicly available constitutively active Cre lines, especially ones with favorable efficiency and specificity profiles for studies where high recombination efficiency is imperative and where tamoxifen administration is contraindicated. Here, we leverage the microglia-specificFcrlsgene to generate mice expressing Cre. Using genomic methods, we show correct positioning of the transgene and intact microglia homeostasis inFcrls-2A-Cremice. CrossingFcrls-2A-Cremice to four different reporters, we demonstrate highly efficient recombination in microglia across differentially sensitive loxP alleles in different genomic contexts, indicating robust applicability of the line. Further, we show that microglia recombine a loxP reporter during early embryonic development, supporting the use of the line for developmental studies. Finally, using immunofluorescence and flow cytometry, we reveal that most border associated macrophages (BAMs) are also targeted whereas only few liver and spleen macrophages and virtually no white blood cell subsets exhibit Cre activity, distinguishing this line from another publicly available Cre line,Cx3cr1-CreM(MMRRC).Fcrls-2A-Cremice are immediately available (JAX Stock #036591) and serve as a valuable addition to the community’s microglia toolbox by providing highly efficient constitutive Cre activity with excellent specificity, particularly for studies where tamoxifen administration is undesirable.Significance StatementThe microglia toolbox is continuously growing with more transgenic lines and most recently even viral tools becoming available. When selecting a Cre driver line, investigators must weigh relative strengths and weaknesses of available lines and carefully make the best choice for their given application. These tradeoffs include (1) availability and ease of employment, (2) chromosomal positioning of Cre with respect to the floxed allele (should not be on the same chromosome for conditional knockout studies), (3) activity level of a given Cre line and thus completeness of recombination across the microglia population, (4) specificity with respect to acceptable off-target cell types and tissues, (5) temporal aspects including earliest onset of Cre expression or inducibility, (6) robustness in disease contexts, and (7) potential perturbation of microglia homeostasis through Cre itself or disruption of the targeting locus. When selecting a mouse line, it is evident that there may not be a one-size-fits all solution but an application-based preference and choice from the diverse repertoire of microglia tools.Fcrls-2A-Cremice are an excellent addition to this toolbox.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Transgenic Targeting ofFcrlsCreates a Highly Efficient Constitutively Active Microglia Cre Line with Differentiated Specificity

Kaiser,

Dattero,

et al. 2023

Preprint

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“…In adult mice, two subpopulations of BAMs have been identified in the perivascular spaces and leptomeninges based on CD38 and major histocompatibility complex class II (MHC2) expression: CD38 + MHC2macrophages are predominantly of embryonic origin and CD38 -MHC2 + macrophages are monocyte-derived and expand from 4 to 12 weeks. 30 Differences in the transcriptional profiles of leptomeningeal BAMs have been identified between neonatal (P4) and adult mice. Neonatal BAMs showed downregulation of genes associated with monocyte recruitment (Ccl2), antigen binding, and antigenpresenting cell response (Cd74), while upregulating genes related to ATP production in mitochondria and cell growth.…”

Section: Macrophagesmentioning

confidence: 99%

“…In contrast, perivascular macrophages are first detected at P10 in mice and are barely detectable in the fetal human brain before gestational week 25, with their numbers only increasing in the perinatal period. In adult mice, two subpopulations of BAMs have been identified in the perivascular spaces and leptomeninges based on CD38 and major histocompatibility complex class II (MHC2) expression: CD38 + MHC2 – macrophages are predominantly of embryonic origin and CD38 – MHC2 + macrophages are monocyte‐derived and expand from 4 to 12 weeks 30 …”

Section: Monocytes and Macrophages In The Developing Central Nervous ...mentioning

confidence: 99%

Monocytes in neonatal stroke and hypoxic‐ischemic encephalopathy: Pathophysiological mechanisms and therapeutic possibilities

Pimentel‐Coelho

2023

Neuroprotection

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Neonatal arterial ischemic stroke (NAIS) and neonatal hypoxic‐ischemic encephalopathy (HIE) are common causes of neurological impairments in infants, for which treatment options are very limited. NAIS and HIE induce an innate immune response that involves the recruitment of peripheral immune cells, including monocytes, into the brain. Monocytes and monocyte‐derived cells have the potential to contribute to both harmful and beneficial pathophysiological processes, such as neuroinflammation and brain repair, but their roles in NAIS and HIE remain poorly understood. Furthermore, recent evidence indicates that monocyte‐derived macrophages can persist in the brain for several months following NAIS and HIE in mice, with possible long‐lasting consequences that are still unknown. This review provides a comprehensive overview of the mechanisms of monocyte infiltration and their potential functions in the ischemic brain, focusing on HIE and NAIS. Therapeutic strategies targeting monocytes and the possibility of using monocytes for cell‐based therapies are also discussed.

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“…Other borderassociated MF (BAM) in the perivascular 'Virchow-Robin' spaces and the leptomeninges are believed to remain under steady-state conditions largely of embryonic origin 7 . Likewise, also parenchymal brain MF are thought to comprise during the life time of healthy mice exclusively YS-derived microglia and no MoMF [8][9][10] . Moreover, even following challenges when monocytes infiltrate the brain to contribute activities distinct from microglia 11 , they often only transiently seed the parenchyma 12,13 , likely since MoMF fail to compete with microglia for to-be-defined niches in the CNS.…”

Section: Introductionmentioning

confidence: 99%

Monocyte-derived microglia withDnmt3amutation cause motor pathology in aging mice

Kim,

Trzebanski,

Shin

et al. 2023

Preprint

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Microglia are established in embryogenesis forming a self-containing cellular compartment resisting seeding with cells derived from adult definitive hematopoiesis. We report that monocyte-derived macrophages (MoMΦ) accumulate in the brain of aging mice with distinct topology, including the nigrostriatum and medulla, but not the frontal cortex. Parenchymal MoMΦ adoptbona fidemicroglia expression profiles. Unlike microglia, these monocyte-derived microglia (MoMg) are due to their hematopoietic origin targets of clonal hematopoiesis (CH). Using a chimeric transfer model, we show that hematopoietic expression of DNMT3AR822H, a prominent mutation in human CH, renders MoMg pathogenic promoting motor deficits resembling atypical Parkinsonian disorders. Collectively, these data establish in a mouse model that MoMg progressively seed the brains of aging healthy mice, accumulate in selected areas, and, when carrying a somatic mutation associated with CH, can contribute to brain pathology.

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A Cre-deleter specific for embryo-derived brain macrophages reveals distinct features of microglia and border macrophages

Cited by 34 publications

References 100 publications

Transgenic Targeting ofFcrlsCreates a Highly Efficient Constitutively Active Microglia Cre Line with Differentiated Specificity

Transgenic Targeting ofFcrlsCreates a Highly Efficient Constitutively Active Microglia Cre Line with Differentiated Specificity

Monocytes in neonatal stroke and hypoxic‐ischemic encephalopathy: Pathophysiological mechanisms and therapeutic possibilities

Monocyte-derived microglia withDnmt3amutation cause motor pathology in aging mice

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