Fig. 5. pMN progenitors intermingle with p2 and p0 progenitor in the ventral VZ in Gli2^-/-;Gli3^xt/xt mutants. (A) In wild-type embryos, Olig2 and Mash1 are expressed in non-overlapping domains in the ventral spinal cord. (B) In Gli2^-/- mutants, the Olig2 pMN domain expands into the ventral midline, but normal segregation between p2 Mash1+ and Olig2+ pMN cells is maintained. (C) In Gli2^-/-;Gli3^xt/xt mutants, Olig2- and Mash1-expressing cells are intermingled, but no cells co-expressing these factors were found. (D) In wild-type embryos, Nkx6.2 marks the p1 and p2 progenitor domains in the VZ, as well as some post-mitotic MNs that form outside the Olig2+ pMN domain (arrowhead). (E) In Gli2^-/- mutants, the dorsal Nkx6.2 domain in p0 and p1 progenitors is not altered, but ventrally Nkx6.2+ MNs extend across the midline (arrowhead), matching the ventral shift in Olig2+ pMN cells. (F) In Gli2^-/-;Gli3^xt/xt mutants, VZ cells expressing Nkx6.2 expanded into the ventral midline, and these cells are intermingled with Olig2+ pMN cells. No cells were found that co-express these factors. Nkx6.2 expression was also detected in some post-mitotic MNs that were located outside of the Olig2+ expression VZ domain in Gli2^-/-;Gli3^xt/xt mutants (arrowhead). (G-I) Schematics summarizing progenitor patterning in wild type, Gli2^-/- and Gli2^-/-;Gli3^xt/xt mutants.