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-7Rα chain and the common γ chain (γC). 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 γC pathway is active in signaling via IL-2. Herein we report the identification and analysis of X. tropicalis IL-7Rα 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. •X. tropicalis IL-7Rα amino acid sequence and structural predictions indicate similarity with IL-7Rα of other species.•The IL-7Rα gene is located on X. tropicalis chromosome 1 and gene synteny analysis shows that X. tropicalis IL-7Rα is flanked by the expected genes.•Phylogenetic analysis of IL-7Rα demonstrates a common ancestor with IL-7Rα of common terrestrial frogs, but not caecilians.•Expression of IL-7Rα was primarily associated with lymphoid tissues and was also detected in the eye of X. tropicalis.•An X. tropicalis IL-7 ortholog was identified using BLAST analysis with a Rhinatrema bivittatum IL-7 sequence.