Jumbled spine and ribs (Jsr): a new mutation on mouse Chromosome 5

Jumbled spine and ribs (Jsr) is an autosomal dominant mutation that results in malformation of the axial skeleton. The vertebrae of mutant mice (Jsr/) are all shorter than those of normal mice (+/+) in the inbred line and sh ow various abnormalities. In addition, several ribs are fused at their prox imal region because of fusion of thoracic vertebrae. In this study, we loca lized the Jsr-mutation on distal Chromosome (Chr) 5 and constructed a high- resolution map. Chromosomal mapping was performed with an inter-subspecific backcross of (CKH-Jsr/+ x MOG) F-1 carrying the Jsr allele and CKH-+/+. Th e predicted gene order around Jsr was determined to be cen-(Epo, Pdgfa, D5M it31, D5Mit374)-(Jsr, Nfe2u, D5Mit99, D5Mit247, D5Mit284, D5Mit292, D5Mit32 7)-D5Mit328-tel. Subsequently, high-resolution mapping concluded the Jsr lo calization to be cen-Nfe2u-1.0cM-Jsr-0.2cM-D5Mit247,292-tel. Jsr/Jsr homozy gotes are alive, as the mutation is not lethal. Based on histological analy sis of mutant embryos, Jsr is hypothesized to be caused by abnormal develop ment of primordial cells in the axial skeleton.