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. Author manuscript; available in PMC: 2022 May 16.
Published in final edited form as: Curr Top Dev Biol. 2020 Nov 19;142:197–231. doi: 10.1016/bs.ctdb.2020.10.009

Fig. 1.

Fig. 1

Organization and specification of dI1s in the spinal cord. (A, B) Six domains of dorsal progenitor neurons (dP1–dP6) arise in the ventricular zone (VZ) in response to BMP/Wnt signals from the roof plate (RP) and retinoic acid (RA) from paraxial mesoderm (PM). This process results in six distinct classes of post-mitotic dorsal neurons (dI1–dI6). The ventral spinal cord is patterned by a gradient of Shh from the floor plate FP. (C) Dorsal interneurons can be distinguished by their expression of distinct complements of transcription factors (Andrews et al., 2017). (D) Model for the specification of dI1s. Both BMP4 and BMP7 can promote Atoh1+ dP1 patterning through BmprIa or BmprIb (chicken), but only BMP4 directs progenitors to differentiate as Lhx2+ dI1s through BmprIb (mouse and chicken) (Andrews et al., 2017).