non synonymous mutations. The significance of these mutations if any is not known. The mouse ortholog has been cloned and exhibits 63% homology to the human gene at the amino acid level. The mouse gene is located on chromosome 1 between the genetic markers Xmv41 and D1Mit166. The mouse gene has two exons (100 and 1064 nucleotides in length), separated by a 461 base pair intron. In the mouse DARC is expressed during embryonic development between days 9.5 and 12. In yellow baboons (Papio cynocephalus) mutations in this gene have been associated with protection from infection with species of the genus Hepatocystis. The ancestral form of extant DARC alleles in humans appears to be the FY*B allele. The gene appears to be under strong purifying selection. The cause of this selective pressure has not yet been identified. Molecular biology Biochemical analysis of the Duffy antigen has shown that it has a high content of α-helical secondary structure - typical of chemokine receptors. Its N-glycans are mostly of the triantennary complex type terminated with α2-3- and α2-6-linked sialic acid residues with bisecting GlcNAc and α1-6-linked fucose at the core. The Duffy antigen is expressed in greater quantities on reticulocytes than on mature erythrocytes. While the Duffy antigen is expressed on bone marrow erythroblasts and circulating erythrocytes it is also found on Purkinje cells of the cerebellum, endothelial cells of thyroid capillaries, the post-capillary venules of some organs including the spleen, liver and kidney and the large pulmonary venules. Duffy antigen has then a very unique cell expression profile in cerebellar neurons, venular endothelial cells and erythroid cells. In some people who lack the Duffy antigen on their erythrocytes it is still expressed in the other cell types. It has two potential N-linked glycosylation sites at asparagine (Asn) 16 and Asn27. The Duffy antigen has been found to act as a multispecific receptor for chemokines of both the C-C and C-X-C families, including: monocyte chemotactic protein-1 (MCP-1) - CCL2 regulated upon activation normal T expressed and secreted (RANTES) - CCL5 melanoma growth stimulatory activity (MSGA-α), KC, neutrophil-activating protein 3 (NAP-3) - CXCL1/CXCL2 and the angiogenic CXC chemokines: Growth related gene alpha (GRO-α) - CXCL1 Platelet factor 4 - CXCL4 ENA-78 - CXCL5 Neutrophil activating peptide-2 (NAP-2) - CXCL7 Interleukin-8 (IL-8) - CXCL8 Consequently, the Fy protein is also known as DARC (Duffy Antigen Receptor for Chemokines). The chemokine binding site on the