Impaired interleukin-3 (IL-3) response of the A/J mouse is caused by a branch point deletion in the IL-3 receptor α subunit gene

Abstract

Interleukin-3 (IL-3) alone does not support hematopoietic colony formation of bone marrow cells from the A/J mouse. To elucidate the molecular lesion in A/J mice, we examined expression of the α and β subunits of the IL-3 receptor (IL-3R). While IL-3Rβ was normally expressed, IL-3Rα was not detectable on the surface of A/J-derived cells by antibody staining. Genetic linkage analysis using recombinant inbred mouse strains between A/J and IL-3-responsive C57BL/6 indicated that the IL-3Rα gene locus was responsible for the impaired IL-3 response in A/J mice. Molecular cloning and characterization of A/J-derived IL-3Rα cDNA revealed that it lacked the sequence corresponding to exon 8, which encodes 10 amino acid residues in the extracellular domain. The aberrant splicing was due to a 5 base pair deletion at the branch point in intron 7 and was reproduced in heterologous cells by transfecting with an IL-3Rα minigene carrying the deleterious intron. The A/J-specific abnormal form of IL-3Rα was localized inside the cells, but not on the cell surface, providing the molecular basis for the impaired IL-3 response in the A/J mouse.