The spinal cord is a valuable model system for understanding how neural cells diversify. But the lineage relationships between the neural stem cells (NSCs) and their descendents - the motoneurons, oligodendrocytes and astrocytes - are still unclear. On p. 581, Capecchi and colleagues use conditional cell ablation to help shed light on this. A long-held model proposes that both motoneurons and oligodendrocytes arise from a common precursor that expresses oligodendrocyte transcription factor (Olig) proteins. The authors tested this by deleting Olig1-expressing NSCs, by using Cre to express diphtheria toxin under the control of Olig1 regulation. As expected, they saw an absence of both motoneurons and oligodentrocytes in this system, but they also saw the continuous generation (and death) of their precursor cells, and observed that oligodendrocyte precursors were generated for much longer than were motoneuron precursors. This refutes the idea that motoneurons and oligodendrocytes come from a single precursor type, and instead the authors propose a new `sequential model' to explain their findings.
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