Analysis of fractalkine receptor CX(3)CR1 function by targeted deletion and green fluorescent protein reporter gene insertion.
The seven-transmembrane receptor CX(3)CR1 is a specific receptor for the novel CX(3)C chemokine fractalkine (FKN) (neurotactin). In vitro data suggest that membrane anchoring of FKN, and the existence of a shed, soluble FKN isoform allow for both adhesive and chemoattractive properties. Expression on activated endothelium and neurons defines FKN as a potential target for therapeutic intervention in inflammatory conditions, particularly central nervous system diseases. To investigate the physiological function of CX(3)CR1-FKN interactions, we generated a mouse strain in which the CX(3)CR1 gene was replaced by a green fluorescent protein (GFP) reporter gene. In addition to the creation of a mutant CX(3)CR1 locus, this approach enabled us to assign murine CX(3)CR1 expression to monocytes, subsets of NK and dendritic cells, and the brain microglia. Analysis of CX(3)CR1-deficient mice indicates that CX(3)CR1 is the only murine FKN receptor. Yet, defying anticipated FKN functions, absence of CX(3)CR1 interferes neither with monocyte extravasation in a peritonitis model nor with DC migration and differentiation in response to microbial antigens or contact sensitizers. Furthermore, a prominent response of CX(3)CR1-deficient microglia to peripheral nerve injury indicates unimpaired neuronal-glial cross talk in the absence of CX(3)CR1.
Jung
S
S
Skirball Institute of Biomolecular Medicine and Howard Hughes Medical Institute New York University Medical Center, New York, New York 10016, USA. jung@saturn.med.nyu.edu
Aliberti
J
J
Graemmel
P
P
Sunshine
M J
MJ
Kreutzberg
G W
GW
Sher
A
A
Littman
D R
DR
D000818:Animals; D000073883:CX3C Chemokine Receptor 1; D015870:Gene Expression; D018390:Gene Targeting; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics; D051379:Mice; D008817:Mice, Mutant Strains; D016254:Mutagenesis, Insertional; D010641:Phenotype; D018121:Receptors, Cytokine / Q000235:genetics / Q000502:physiology*; D015728:Receptors, HIV / Q000235:genetics / Q000502:physiology*
D000073883:CX3C Chemokine Receptor 1; D008164:Luminescent Proteins; D018121:Receptors, Cytokine; D015728:Receptors, HIV; D049452:Green Fluorescent Proteins