CHARACTERIZATION OF CDNAS ENCODING THE MURINE INTERLEUKIN-2 RECEPTOR (IL-2R) GAMMA-CHAIN - CHROMOSOMAL MAPPING AND TISSUE-SPECIFICITY OF IL-2R GAMMA-CHAIN EXPRESSION

The IL-2R gamma chain (IL-2Rgamma) is an essential component of high- and intermediate-affinity IL-2Rs, playing critical roles for ligand bi nding and internalization. Recently, our laboratory has demonstrated t hat IL-2Rgamma mutation results in X chromosome-linked severe combined immunodeficiency in humans, suggesting that IL-2Rgamma plays a vital role in thymic maturation of human T cells. We now report the isolatio n and characterization of cDNAs encoding murine IL-2Rgamma. The open r eading frame encodes 369 aa, identical in length to that encoded by th e human IL-2Rgamma cDNA. Murine IL-2Rgamma and human IL-2Rgamma have 6 9% and 70% identity at the nucleotide and amino acid levels, respectiv ely. As expected, the murine IL-2Rgamma retains the WSXWS motif and fo ur cysteine residues characteristic of cytokine receptor superfamily m embers. IL-2Rgamma mRNA distribution shows significant tissue specific ity, with particularly high-level expression in spleen and thymus, and higher expression in single-positive (CD4+8- or CD4-8+)-enriched thym ocytes than in double-negative (CD4-8-) thymocytes. Finally, we have l ocalized the murine IL-2Rgamma gene, Il2rg, to the X chromosome betwee n Rsvp and Plp and demonstrated that a defect in IL-2Rgamma is not res ponsible for the X chromosome-linked xid mutation, which maps to this same region. The cloning of the murine IL-2Rgamma cDNA will facilitate the investigation of the role of this protein in lymphocyte function and thymic development.