Recently, many genes encoding the members of the cytokine receptor superfamily (CRSF), which have common structural features, have been characterized. Analyses on the structures of the genes encoding the α subunits of human IL-3 (hIL-3Rα) and granulocyte-macrophage colony-stimulating factor receptors (hGMRα) revealed that they have the structural features common to all members of the CRSF (i.e., conservation of the intron phase pattern as "1-2-1-0-1" rule in the fibronectin type III domains located in extracellular segments of type I cytokine receptor subunits. This finding led us to propose a possible model for gene evolution for the CRSF. We pointed out that the CRSF genes derived from a putative common ancestral gene. In addition to these common features, we found an additional intron that is unique to the IL-3Rα and the GMRα genes. This additional intron suggests that the IL-3Rα and the GMRα genes evolved closely in the evolution process of the CRSF genes. This evidence and results of recent studies on the evolution of mammalian X chromosome make it tempting to speculate that a putative common ancestral gene of the subfamily including IL-3Rα, GMRα, and IL-5Rα emerged in an autosome at least before the divergence of marsupials and eutherian mammals, early in the 200 million-year history of mammals. (J ALLERGY CLIN IMMUNOL 1995;96:1115-25.).
- Cytokine receptor
- cytokine receptor superfamily
- gene evolution
- gene structure