Evolutionary conservation of the IL-7R signaling pathway in Xenopus tropicalis

IL-7 is a group 1 cytokine characterized by a four-helix bundle structure. IL-7 is a growth factor for B and T cells. The receptor for IL-7 is a heterodimer of the IL-7R alpha chain and the common gamma chain (gamma C). An intact IL-7 signaling pathway is necessary for T cell development in mammals, however IL-7 may play only a minor role in T cell development early in vertebrate evolution and other cytokine signaling pathways may be utilized in place of IL-7, at least in teleost fish. The status of the IL-7 signaling pathway in amphibians is unknown, except that the gamma C pathway is active in signaling via IL-2. Herein we report the identification and analysis of X. tropicalis IL-7R alpha and IL-7. The findings suggest that IL-7/IL-7 receptor signaling strongly resembles that of higher vertebrates, but points to some structural and expression differences that may be unique to amphibians.