Fig. 2.

MN fate specification and consolidation. A combination of extrinsic signals including Shh, RA, and FGFs cooperate with intrinsic mechanisms that involve Olig2, Neurogenin-2 (Neurog2), and Lhx3 to promote the specification of newly born MN. GDE2 produced by the newly born MN acts in an on-cell autonomous manner to promote MN progenitor differentiation. Lhx3, Isl1, NLI, LMO4, and Hb9 act together to consolidate MN identity. Isl1 may additionally contribute to the survival of newly born MNs. FGFs fibroblast growth factors, RA retinoic acid, Shh Sonic Hedgehog, NLI nuclear Lim-domain interactor, GDE2 glycerophosphodiester phosphodiesterase 2