The CX3C chemokine receptor 1 (CX3CR1) gene encodes a G protein-coupled receptor that primarily functions to recognize and bind the CX3CL1 chemokine protein. The CX3CR1-CX3CL1 signaling pathway plays a crucial role in regulating immune cell migration during inflammatory responses, neuronal migration, and synapse formation, among other physiological and pathological processes. The dysregulation of CX3CR1 has been implicated in various diseases, including inflammatory diseases, cancer, and neurological disorders. As such, the CX3CR1-CX3CL1 signaling pathway is widely studied to understand the biological processes of the immune and nervous systems and the pathogenesis of related diseases. CX3CR1 is predominantly expressed in the immune and nervous systems, particularly on the surface of mononuclear macrophages and microglia. It is also expressed in monocytes, circulating T cell subsets, natural killer cells, and dendritic cells.^[1]

Cx3cr1-iCre mice are generated using gene editing technology to replace the coding sequence (CDS) region of the endogenous mouse Cx3cr1 gene with an improved Cre recombinase (iCre) expression element. This results in an expression pattern of Cre recombinase that is similar to that of the endogenous gene. When these mice are crossed with mice containing a loxP site-flanked sequence, Cre recombinase-mediated recombination leads to deletion of the flanked sequence in brain microglia and macrophages in other parts of the offspring mice.