| First Author | Zhao XF | Year | 2019 |
| Journal | eNeuro | PubMed ID | 31201215 |
| Mgi Jnum | J:276175 | Mgi Id | MGI:6315058 |
| Doi | 10.1523/ENEURO.0114-19.2019 | Citation | Zhao XF, et al. (2019) Targeting microglia using Cx3cr1-cre lines: revisiting the specificity. eNeuro :ENEURO.0114-19.2019 |
| abstractText | Microglia play a pivotal role in maintaining homeostasis of the CNS. There is growing interest in understanding how microglia influence normal brain function and disease progression. Several microglia-specific Cx3cr1-Cre lines have been developed and have become indispensable tools in many investigations of microglial function. However, some recent studies have reported that these lines may have significant leakage into neurons. Other studies have reported that Cx3cr1 is expressed in non-microglial cells, including neurons and astrocytes, in vitro or in vivo either during brain development or upon neurological insult. All these reports raise serious concerns about the trustworthiness of these Cre-lines and whether the conclusions drawn from previous studies are valid. Here, we found that a floxed fluorescent reporter mouse line which has been frequently used to verify Cre lines displayed spontaneous expression of the GFP reporter, independent of Cre recombinase, thus revealing a potential caveat in assessing cre lines. We further confirmed that two Cx3cr1-Cre mouse lines can drive fluorescent reporter expression largely restrictively in microglia. Finally, we clarified that these two mouse lines maintain microglia-specific expression even following excitatory injury. Together, our findings confirm that two previously created Cx3cr1-Cre lines remain as invaluable tools for studying microglia. Moreover, to ensure the quality of data generated and the soundness of conclusions drawn from such data, it should be compulsory to thoroughly examine reporter lines for spontaneous leakiness when labeling cells to study CNS function and diseases.Significance Statement Microglia-specific Cre-lines are essential for studying the role of microglia in the CNS. Several Cx3cr1-Cre lines have been developed and used in a number of landmark studies. However, there is growing concern in the microglia research community regarding potential leakiness of Cre-lines into neurons. The conclusions drawn from previous studies are also being questioned and key ongoing studies have been stalled. We found that a GFP-reporter mouse lines used in a previous study displays spontaneous leakiness into neurons, independent of Cre recombinase. Furthermore, we confirmed that two Cre-lines are microglia-specific and thus can be redeployed without hesitation. Our study also suggests that testing for potential leakiness of GFP-reporter lines should be included as a control in cell-tracing experiments. |
