Cloning and sequence analysis of the immediate promoter region and cDNA of porcine granulocyte colony-stimulating factor.

Granulocyte colony-stimulating factor (G-CSF) is a cytokine that stimulates the proliferation and differentiation of hematopoietic progenitor cells committed to the neutrophil/granulocyte lineage. Recombinant G-CSF (rG-CSF) is routinely used in the prevention of chemotherapy-induced neutropenia and in the setting of bone marrow transplantation. Chronic idiopathic and congenital neutropenic disorders also show improvement after rG-CSF injections. Applications of either rG-CSF or G-CSF gene transfected cells into mice give rise to leukocytosis, which can be measured easily. This makes G-CSF a versatile tool for studying systemic effects of therapeutic proteins delivered by genetically modified cells in vivo. Although the biological activity of G-CSF is not species-specific, studies on long-term expression would require the use of species-identical proteins in order to avoid host immune reactions against the foreign gene product. Because of the physiological and immunological similarity of pigs and human, the pig has become an important large-animal model for biomedical research. We have therefore cloned porcine G-CSF cDNA from RNA isolated from pig PBLs. Pig G-CSF is a 195-amino-acid polypeptide that shares a high degree of homology to human (78%), murine (71%) as well as rat (68%) G-CSF. In contrast to human and murine, but not to rat G-CSF, a different ATG translation start codon is used, resulting in a shorter, but still functional signal sequence.