Fig. 3. Dorsoventral patterning in spinal cord is not affected by the Nkx2.9 mutation. Immunohistochemistry on transverse sections of spinal cord at forelimb (A-D,G,H) and hindlimb level (E,F) demonstrates the expression of marker genes for distinct subpopulations of neuronal progenitors in E10.5 heterozygous (A,C,E,G) and homozygous (B,D,F,H) Nkx2.9 mutant embryos. Immunofluorescence staining for HNF3ß marks the floorplate (A,B), Nkx2.2 (red in C-H) and Isl1 (green in C-F) label V3 interneurons and motoneurons, respectively. Pax6 (green in G,H) labels all neuronal precursors except V3 neurons and floorplate. No major differences are seen between heterozygous and homozygous animals. Note, however, individual Isl1-positive cells within the Nkx2.2 domain of the neural tube at hindlimb level (E,F). In situ hybridization with Sim1- (I,J) and Dbx2- (K,L) specific probes on transverse sections illustrates normal production of V3 neurons and dorsoventral patterning of the V1 progenitor domain in neural tube of Nkx2.9-deficient embryos, respectively. (I-L) Heterozygous (I,K) and homozygous (J,L) mutant embryos.

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