Autosomal telomere exchange results in the rapid amplification and dispersion of Csf2ra genes in wild-derived mice

Common laboratory strains such as C57BL/6J carry a single Csf2ra gene that maps to the distal end of Chromosome (Chr) 19. Here we report that several species of wild mice contain multiple Csf2ra genes. Using interspecific bac kcross mapping and in situ hybridization, we demonstrate that one of these species, Mus spretus, carries four Csf2ra genes dispersed among the distal tips of Chrs 4, 10, 13, and 19. Our data further suggest that these additio nal Csf2ra genes are not generated by retrotransposition, but rather by non homologous subtelomeric exchanges that could be mediated in part by ribosom al genes located at the subtelomeric regions of Chrs 4, 13, and 19. Althoug h we do not know whether these additional Csf2ra genes are functionally act ive, our studies suggest that subtelomeric exchange provides a potent means for rapid gene amplification in the mouse.