Expression domains and network interactions of key signaling and transcription factors involved in caudal spinal cord maturation.

(A) Schematic representation of the caudal end of a stage HH10-11 chick embryo (dorsal view). Expression domains of Fgf8 (red) and Wnt8c (magenta) signaling factors, and the Retinoic Acid synthesizing enzyme Raldh2 (blue), are superimposed on the diagram (based on [27]). Expression domain of relevant transcription factors are indicated on the left (based on [15]). (B) Expression domains of key transcription factors involved in caudal spinal cord maturation. Embryos are stage HH10-11. Scale bar is 200μm. Arrowheads indicates the anterior boundary of the last formed somite. Transcription of the T/Bra gene along the embryo’s midline is in the notochord underlying the neural tissue, where it is absent. (C) Postulated gene regulatory network showing interaction between signaling and transcription factors (based on [15, 20, 25, 27]).