Genomic organization and assignment of the interleukin 7 gene (IL7) to porcine chromosome 4q11-->q13 by FISH and by analysis of radiation hybrid panels

Interleukin 7 (IL7) is a cytokine that has many immunological functions, including regulation of hematopoiesis and peripheral lymphocytes. cDNA and a genomic DNA segment containing the porcine IL7 gene were isolated and sequenced, showing that porcine IL7 consists of 176 amino acids and that its gene spans over about 13 kb of genomic DNA. Porcine IL7 has 85% and 73% homology with human IL7 in terms of the nucleotide and amino acid sequences, respectively. Whereas the murine IL7 gene does not have an exon corresponding to human exon 5 (Lupton et al., 1990), the porcine IL7 gene was found to contain the same exon-intron structure as the human gene. These findings, together with the upstream structure of the cDNA elucidated in the present study, indicate that the relationship between swine and human IL7 is closer than that between mouse and human IL7. The IL7 gene was mapped to swine chromosome 4q11-->q13 by fluorescence in situ hybridization and, using a radiation hybrid panel, was localized between microsatellite markers Sw1336 and Sw1073 on the same chromosome.