Figure 2. Shh signaling is required for LMC specification in chick spinal cord.

(A) IHC analyses in chick spinal cords electroporated with sh-Shh and sh-vector construct. ISH analysis showed the reduced expression of chick Shh in sh-Shh electroporated chick embryo but not in control sh-vector injected chick embryo. Knock-down of chick Shh did not affect the proliferation (BrdU) or survival (cCasp3) of neural progenitor cells and ventral neural patterning (Olig2 and Nkx2.2). (B) Knock-down of chick Shh reduced the number of LMCl (Hb9⁺/FoxP1⁺) neurons but had no effect on other motor columns such as LMCm, MMC, and HMC and consequently reduced the number of total MNs compared to the uninjected control side. +, electroporated side; -, non-electroporated control side. (C) Quantification of the relative intensity of Shh ISH signal in motor neurons, % marker⁺ (BrdU, Nkx2.2, Olig2, and cCasp3) cells relative to uninjected side and % motor columns relative to uninjected side of the spinal cord. Each set of chick electroporation experiments in this figure was repeated independently at least three times with 6 to 10 embryos. Embryos were harvested 4 days post electroporation (dpe). Data are mean ± s.d. **p<0.001, ***p<0.0001; ns, non-significant (Student’s t-test). n = 6 ~ 15 independent images per each sample. Scale bars: 100 μm.