Proc Natl Acad Sci U S A. 2016 Mar 22;113(12):E1738-46. doi: 10.1073/pnas.1525528113. Epub 2016 Feb 16.

New tools for studying microglia in the mouse and human CNS.

Bennett ML¹, Bennett FC², Liddelow SA³, Ajami B⁴, Zamanian JL⁵, Fernhoff NB⁶, Mulinyawe SB⁵, Bohlen CJ⁵, Adil A⁵, Tucker A⁵, Weissman IL⁶, Chang EF⁷, Li G⁸, Grant GA⁸, Hayden Gephart MG⁸, Barres BA¹.

Author information

1: Department of Neurobiology, Stanford University School of Medicine, Stanford, CA 94305; marikobennett@stanford.edu barres@stanford.edu.
2: Department of Neurobiology, Stanford University School of Medicine, Stanford, CA 94305; Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA 94305;
3: Department of Neurobiology, Stanford University School of Medicine, Stanford, CA 94305; Department of Pharmacology and Therapeutics, University of Melbourne, Melbourne, VIC, Australia, 3010;
4: Department of Neurology, Stanford University School of Medicine, Stanford, CA 94305;
5: Department of Neurobiology, Stanford University School of Medicine, Stanford, CA 94305;
6: Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305; Ludwig Center for Cancer Stem Cell Research and Medicine, Stanford University School of Medicine, Stanford, CA 94305; Stanford Cancer Institute, Stanford University School of Medicine, Stanford, CA 94305; Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305;
7: University of California, San Francisco Epilepsy Center, University of California, San Francisco, CA 94143;
8: Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305.

Abstract

The specific function of microglia, the tissue resident macrophages of the brain and spinal cord, has been difficult to ascertain because of a lack of tools to distinguish microglia from other immune cells, thereby limiting specific immunostaining, purification, and manipulation. Because of their unique developmental origins and predicted functions, the distinction of microglia from other myeloid cells is critically important for understanding brain development and disease; better tools would greatly facilitate studies of microglia function in the developing, adult, and injured CNS. Here, we identify transmembrane protein 119 (Tmem119), a cell-surface protein of unknown function, as a highly expressed microglia-specific marker in both mouse and human. We developed monoclonal antibodies to its intracellular and extracellular domains that enable the immunostaining of microglia in histological sections in healthy and diseased brains, as well as isolation of pure nonactivated microglia by FACS. Using our antibodies, we provide, to our knowledge, the first RNAseq profiles of highly pure mouse microglia during development and after an immune challenge. We used these to demonstrate that mouse microglia mature by the second postnatal week and to predict novel microglial functions. Together, we anticipate these resources will be valuable for the future study and understanding of microglia in health and disease.