Fig. 3. MNs, V2 and V1 cells are generated in the ventral spinal cord of Gli2^-/-;Gli3^xt/xt mutant embryos but are intermingled. (A-C) MNs (HB9+) and V1 (En1+) cells are generated in double mutants but extend into the ventral midline. (C) Quantification of MN number in thoracic and lumbar regions of wild-type and Gli2^-/-;Gli3^xt/xt mutants. (D,E) In wild-type embryos, V2a (Chx10) and V2b (Gata3) cells develop as intermingled sub-populations dorsal to V1 cells. In Gli2^-/-;Gli3^xt/xt mutants, both classes of V2 cells were generated in the ventral midline but retained their intermingled organization. (F) Quantification of V2a and V2b cells in Gli2^-/-;Gli3^xt/xt mutants, compared with wild type. (G,H) In wild-type embryos, V0 (Evx1+) and V1 (En1+) cells differentiate as discrete populations. In Gli2^-/-;Gli3^xt/xt mutants, V0 cells show a limited expansion into the V1 domain. V0 and V1 intermingling is less pronounced at lumbar levels (data not shown). (I) Quantification of V1 cells in Gli2^-/-;Gli3^xt/xt mutants. (J,K) MNs, V2 and V1 neurons intermingle in Gli2^-/-;Gli3^xt/xt mutants. (L-P) Altered number of Olig2+ pMN cells in Gli2^-/-;Gli3^xt/xt mutants. Sections through mid-thoracic (L,M) and lumbar (O,P) regions. (N) Quantification Olig2 pMN numbers in wild-type and Gli2^-/-;Gli3^xt/xt mutants. Histograms indicate average cell counts/section, error bars indicate s.e.m. (Q,R) Pax6 expression in pMN cells. Pax6 is normally expressed weakly in dorsally derived MNs (bracket, Q). In Gli2^-/-;Gli3^xt/xt mutants, strong Pax6 expression extends to the ventral midline (R).