Mice hemizygous for the BAC Cx3cl1105Δ transgene are viable and fertile. The BAC has been modified to place a nonsense mutation at amino acid 105, in exon 3, of Cx3cl1 (chemokine (C-X3-C motif) ligand 1) gene followed by a myc-tag. CX3CL1 is the ligand for the chemokine receptor CX3CR1, and is involved in integrin-independent adhesion. CX3CL1 is expressed in mature neurons in the hippocampus, striatum, and cortical layer II and in epithelial cell layers. Expression is also seen in the lung in alveolar and bronchial epithelial cells, including Clara cells. In the kidney CX3CL1 is expressed in tubular epithelial cells and glomeruli, and in goblet cells and cells along the proximal and distal gastrointestinal tract. This mutation, in the mucin stalk domain, creates a truncated CX3CL1 protein lacking the mucin stalk, the transmembrane region, and the cytoplasmic tail. The mucin stalk functions to present the CX3C chemokine module, removal of which creates a secreted, truncated CX3CL1 protein. Cx3cl1105Δ mice are useful when studying the differential chemoattractive activities of membrane tethered verses shed CX3CL1 proteins.
