Low back pain is a common clinical problem that is attributed to degeneration of the intervertebral disc (IVD), and specifically the inner nucleus pulposus. Treatments are limited owing to lack of knowledge about disc development, maintenance and degeneration. McCann et al. now report a mouse model that allows lineage-tracing experiments of cells of the IVD, and show that all cells in the nucleus pulposus are derived from the embryonic notochord. These mice can be used to investigate mechanisms regulating the transition from notochord to nucleus pulposus cells, which might aid the development of regenerative therapies for IVD degeneration. Page 73

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