Analyses of microglia effector function using CX3CR1-GFP knock-in mice.

The generation of bone marrow radiation chimeric mice is a beneficial tool to utilize when studying inflammation of the central nervous system (CNS). It is widely accepted that blood-derived progenitors are capable of populating the CNS during chronic diseases and severe injuries; however, they are neither consistent nor efficient in doing so. The lack of the appropriate recruitment could explain delays in recovery and repair after an increase of toxic proteins in chronic neurodegenerative diseases. With the ingenious development of bone marrow chimeric mice, some of these concerns can be addressed and allow us to hypothesize about further implications and possible mechanisms that may lead to medicinal applications. Bone marrow chimeric mice are often used to distinguish the intrinsic versus extrinsic effects of specific mutations. In our case, chimeras help us to better understand the role of CX3CR1 in microglia and peripheral myeloid cells. To detect cell autonomous effects on myeloid cell differentiation, CX3CR1-deficient mice are used as donors and wild-type mice are used as recipients. In order to detect effects on the "immune cell environment," wild-type donors are used for the transfer into Cx 3 cr1 (-/-) recipients. The resulting chimeric mice can then be used for the analysis of microglial motility, regulation of neuroinflammation, and persistence. This technique can be applied to a broad spectrum of research ranging from neurodegenerative diseases to viral and parasitic pathogenicity and everything in between. This protocol describes the approach to generate chimeric mice and analyze the role of CX3CR1 in CNS inflammation in bone marrow radiation chimeras.