Fig. 1

Marker analysis of the LFP domain.

(A) Schematic drawings of the zebrafish ventral spinal cord at 24 hpf in a dorsal view (a), lateral view (b), and cross-section (c). The lateral floor plate domain, consisting of LFP cells and KA3 interneurons, flanks the medial floor plate (MFP). The motor neuron domain locates dorsal to the LFP domain, which contains motor neuron progenitors (pMN), motor neurons (MN), and Kolmer-Agduhr′ interneurons (KA′). KA interneurons, including KA′ and KA′′ cells, represent a unique class of GABAergic interneurons that are in contact with the cerebrospinal fluid and are implicated in regulating the swimming behavior in zebrafish [35], [47], [48]. Marker expression in MFP, LFP and KA3 cells are indicated on the right. N: notochord. (B) KA′′ cells, labeled by tal2 expression (arrows, red), are discontinuously distributed flanking the medial floor plate (arrowhead) along the anterior-posterior axis. Cell nuclei were labeled by Draq5 staining (green). (C) All tal2-positive cells (arrows, red) in the LFP domain also express pan-neuronal marker HuC (green). (D–E) All GFP-expressing cells in the LFP region (arrows, green) in Gata2-GFP fish also co-express tal2 (D, red) and GABA (E, red). (F–G) Wild type embryos were co-labeled with nkx2.9 (F, green) or nkx2.2a (G, green) together with tal2 (red). tal2-expressing KA′′ cells (arrows) show lower expression of nkx2.9 and nkx2.2a compared to their neighboring cells. Embryos shown are at 21 hpf (B), 30 hpf (C), 25 hpf (D), 27 hpf (E), and 18 hpf (F, G). B, D, F, and G show dorsal views, and C and E represent lateral views. Scale bars: 20 μm.