Deletion of the Murine Duffy Gene (Dfy) Reveals that the Duffy Receptor Is Functionally Redundant

Abstract

All of the antigenic determinants of the Duffy blood group system are in a glycoprotein (gp-Fy), which is encoded by a single-copy gene (FY) located on chromosome 1. gp-Fy is also produced in several cell types, including endothelial cells of capillary and postcapillary venules, the epithelial cell of kidney collecting ducts, lung alveoli, and the Purkinje cells of the cerebellum. This protein, which spans the cell membrane seven times, is a member of the superfamily of chemokine receptors and a malarial parasite receptor. The mouse Duffy gene (Dfy) homolog of human FY is also a single-copy gene, which maps in a region of conserved synteny with FY and produces a glycoprotein with 60% homology to the human protein. The mouse Duffy-like protein also binds chemokines. To study the biological role of gp-Fy, we generated a mouse strain in which Dfy was deleted. These homozygous Dfy ؊/؊ mice were indistinguishable in size, development, and health from wild-type and heterozygous littermates. We also examined components of the immune system and found no differences in lymph nodes or peripheral blood leukocyte levels between knockout and wild-type mice. The gross and histological anatomy of the thymus, spleen, lung, and brain showed no significant differences between mutants and wild-type mice. There was no indication of an overall difference between the knockout and wild-type mice in systematic neurological examinations. The only significant difference between Dfy ؊/؊ and Dfy ؉/؉ mice that we found was in neutrophil migration in peritoneal inflammations induced by lipopolysaccharide and thioglycolate. In mice homozygous for the deletion, there was less neutrophil recruitment into the peritoneal cavity and neutrophil influx in the intestines and lungs than in wild-type mice. Despite this, the susceptibility to Staphylococcus aureus infection was the same in the absence and in the presence of gp-Fy. Our results indicate that gp-Fy is functionally a redundant protein that may participate in the neutrophil migratory process.

Role of the pulmonary epithelium and inflammatory signals in acute lung injury

“…However, it does not transmit a signal via G proteins, as occurs with other seven-transmembrane receptors. The receptor serves as a chemokine reservoir, regulating tissue and plasma chemokine levels, thus affecting neutrophil migration to various tissues, including the lung [80][81][82][83]. Mice deficient in this receptor demonstrate impaired neutrophil migration to the lung, intestines and peritoneum, and altered chemokine levels in the serum and tissue [82,83].…”

“…The receptor serves as a chemokine reservoir, regulating tissue and plasma chemokine levels, thus affecting neutrophil migration to various tissues, including the lung [80][81][82][83]. Mice deficient in this receptor demonstrate impaired neutrophil migration to the lung, intestines and peritoneum, and altered chemokine levels in the serum and tissue [82,83]. In endothelial cells expressing the Duffy antigen, neutrophil migration toward GRO-α/CXCL1 and IL-8 (IL-8/CXCL8) was enhanced, suggesting that the Duffy antigen participates in the movement of neutrophil chemokines across the endothelium [81].…”

Developmental Expression of Two CXC Chemokines, Mip-2 and Kc, and Their Receptors

“…12 Again, the role for mDuffy in neuronal development and neurological functioning is not at all clear. There is no evidence that this receptor transduces an intracellular signal once ligand binds, though it is reported to serve as a clearance receptor to remove excess chemokine after an inflammatory response.…”

“…Alternatively, mDuffy may be involved in the presentation of ligand to other functional chemokine receptors. Since loss of mDuffy was without consequence in that no neurological deficiencies were observed, 12 it has been proposed that if this receptor has a function, there is redundancy such that loss of mDuffy has no phenotypic consequence.…”

“…In contrast, the mDuffy −/− mice exhibit a fairly normal phenotype. 12 To obtain additional insight into the phenotypic properties of the mCXCR2 −/− mice, we examined the developmental expression of the murine CXC chemokines KC, (a cloning designation based on ordinate and abscissa position) macrophage inflammatory protein-2 (MIP-2), mCXCR2 and mDuffy between 11.5 and 13.5 days of development, using immunohistochemical staining, reverse transcriptase-polymerase chain reaction (RT-PCR) analyses, and Western blot analyses. The developmental expression of these chemokines and their receptors was not surprising, but several unexpected findings were uncovered which may provide insight into the failure of the mCXCR2 −/− mice to thrive in a non-infectious, but stressful environment.…”