Fig. 3. Olig3 is required to determine the fate of class A neurons in rhombomere 4. Immunohistological analyses (antibodies as labeled) of the alar plate of rhombomere 4 of control (Olig3^+/-) and Olig3 homozygous mutant mice at E11.5. (A,B) In control animals, Lbx1⁺ neurons were restricted to the ventral alar plate. In Olig3 mutant mice, ectopic Lbx1⁺ neurons were present. (C,D) In Olig3 mutant mice, Tlx3⁺ (dA3^*) neurons were generated in reduced numbers and co-expressed Lbx1. (E,F) Phox2b⁺ dA3 neurons were not present in Olig3 mutant mice, and the expression domain of Ptf1a was expanded. (G-J) In the dorsal alar plate of Olig3 mutant mice, Lhx1/5⁺/Lbx1⁺, Lhx1/5⁺/Lbx1^- and Lbx1⁺/Pax2⁺ neurons arose in an apparently intermingled manner. Note that G,I and H,J show identical sections, which were stained with antibodies against Lbx1, Pax2 and Lhx1/5; G,H and I,J display Lbx1/Pax2 and Lbx1/Lhx1/5 signals, respectively. Scale bar: 50 µm.