Figure 6

pMN-restricted and pMN-patchy clones acquire thoracic identity after in vitro expansion, regardless of their origin of isolation. (A, M) Contour plots of dissociated cells from e9.5 brachial (A) or thoracic (M) trunks from Nkx6.1::IRES::eGFP^+/- mice. (B, C) Immunohistochemistry with HoxC6 (B) and Hb9 (red) and Tuj1 (green) (C) of MNs born from non-proliferating brachial Nkx6.1⁺ progenitors. These motor neurons express low levels of HoxC6. (D-I) Immunohistochemistry for HoxC6 (D) or HoxC9 (G) of brachial pMN-restricted clones that contain either Hb9⁺Tuj1⁺ (E, F) or Isl1/2⁺Tuj1⁺ (H, I) neurons. Brachial-derived pMN-restricted clones lose expression of HoxC6 and now express HoxC9. (J-L) Brachial-derived pMN-patchy clones express HoxC9 (J) even in neurons that have lost their ventral identity (white arrows, K, L). (N, O) Immunohistochemistry with HoxC9 (N) and Isl1/2 (red) and Tuj1 (green) (O) of MNs born from non-proliferating thoracic Nkx6.1⁺ progenitors. These MNs express HoxC9. (P-U) Immunohistochemistry for HoxC9 (P) or HoxD10 (S) of thoracic pMN-restricted clones containing Isl1/2⁺ Tuj1⁺ neurons. These neurons do not express HoxD10, a marker of lumbar MNs. (V-X) Immunohistochemistry for HoxC9 (V) of thoracic pMN-patchy clones that express Isl1/2 (W, X; red) in a subset of Tuj1⁺ neurons (X; green). Thoracic-derived pMN-patchy clones (white arrows) express HoxC9 even in neurons that have lost their ventral identity.