Figure 4

Ventral subtype-restricted progenitors are present at low frequencies in the spinal cord. (A) Diagram of sorted Nkx6.1⁺ progenitor fates after culture for several days. (B-D) Immunohistochemical analysis for Sox3 and Nkx6.1 in clones derived from single Nkx6.1⁺ proliferating progenitors. The progenitor state of the cell is revealed by Sox3 (green). Negative clones have no expression of Nkx6.1 (B), patchy clones have some cells that express Nkx6.1 (C; yellow cells) and positive clones have more than 95% of cells that express Nkx6.1 (D). (E) Fractions of three different types of clones observed in cultures from sorted e9.0 (red), e9.5 (green) or e10.0 (blue) Nkx6.1⁺ progenitors. (n = 420 clones from 6 experiments at e9.5; n = 234 clones at e9.0; and n = 124 clones at e10.0 from 3 experiments for the latter two time points). (F) Fraction of eGFP⁺ cells that forms clones in culture at three developmental stages. (G) Frequency plot for the three classes of subtype-restricted clones isolated from Nkx6.1⁺ progenitors (n = 52 Nkx6.1⁺ clones). Bars represent mean ± s.e.m in all plots. (H-P) Expression of Nkx6.1, Olig2 and Nkx2.2 in subtype-restricted progenitors derived from a presumed p2 (H-J), pMN (K-M) or p3 (N-P) progenitor. No clones displayed a mixture of Olig2⁺ and Nkx2.2⁺ progenitors.