Fig. 2. Gsh2 mutant embryos do not generate dI3 neurons. (A-F) Changes in dorsal neuron differentiation in E10.5 Gsh2 knockout (KO) embryos. (A) Lbx1⁺ dI4-dI6 neurons are still generated in the Gsh2^-/- mutant spinal cord. (B) Foxd3⁺ dI2 neurons are increased in Gsh2^-/- mutant embryos, whereas Isl1⁺ dI3 neurons are almost completely absent (C). The arrow in C indicates the few remaining dI3 cells. (D) Ventral Brn3a expression (arrow) is unchanged in the mutant, indicating a normal development of dI5 neurons. (E) The dorsal population of Tlx3⁺ neurons (arrow) is missing in the Gsh2 mutant cord, confirming the loss of dI3 neurons, while Tlx3 expression in dI5 neurons is not affected. (F) The loss of Isl1⁺ dI3 neurons is partially offset by an increase in Foxd3⁺ dI2 neurons. (G-L) Changes in transcription factor expression at E11.5 in Gsh2 mutant embryos. In Gsh2^-/- mutants, Lhx1/5⁺ (G) and Foxd3⁺ neurons (H) are generated from the dI3 progenitor domain (arrows in G and H) at the expense of Isl1⁺ (I) and Otp⁺ (K) dI3 neurons (arrows). (J) There is a slight dorsal expansion of dI4 neurons expressing Pax2 (arrow). (L) Cell counts of Foxd3- and Isl1-positive cells in Gsh2 KO mice (-/-) show a loss of >95% of dI3 neurons and a concomitant increase in dI2 neurons, when compared with age matched wild-type embryos (+/+). Drg, dorsal root ganglion.