Transient expression of Gdf11 in the developing spinal cord. Detection of Gdf11 expression by in situ hybridization on cross-sectioned spinal cord tissues. A–C, At e10 Gdf11 is expressed in cells located lateral to the progenitor domain at brachial (A), thoracic (B) and lumbar (C) levels of the spinal cord. D–F, Downregulation of Gdf11 expression is observed in mature neurons at e10.5 (D, arrow). G, H, The expression level of Gdf11 continues to decline through e11.5 (G) and e12.5 (H). Asterisk (*) indicates dorsal root ganglia. Scale bars, 100 μm.