Figure 4.

Bmi1 depletion converts forelimb LMC MNs to a PGC fate. (A–D) Expression of the LMC markers FoxP1 and Raldh2 is diminished after depletion of Bmi1 at brachial levels. (E,F) Expression of the PGC marker pSmad is detected at brachial levels and coexpresses Hoxc9. Not all ectopic Hoxc9 cells label with pSmad, as Hoxc9 is derepressed in non-MN cells. (G,H) Expression of pan-MN markers Hb9 and Lhx3 is not affected at brachial levels. (I) Summary showing changes in MN molecular identity following Bmi1 depletion. (J,K) Vibratome sections of chick embryos electroporated with a Hb9∷GFP construct to label motor axons (green). Sympathetic chain ganglia are indicated by yellow arrows and are stained by Isl1/2. (L,M) MNs coelectroporated with Bmi1 dsRNA and Hb9∷GFP express ectopic Hoxc9, and their axons are redirected to the sympathetic chain ganglia at brachial levels.