tal2 expression in the lateral floor plate depends on nkx2.2a, nkx2.2b and nkx2.9. (A,B) Control (A) and Mo-nkx2.9-injected (B) zebrafish embryo. Knockdown of nkx2.9 leads to a reduction of tal2-positive cells in the lateral floor plate (arrow) but dorsal tal2-positive cells are unaffected (arrowhead). (C,D) Control (C) and Mo-nkx2.9/Mo-nkx2.2a-injected (D) embryos. There is a reduction of tal2-positive cells in the lateral floor plate, whereas tal2-expressing cells (arrowhead) further dorsal in the spinal cord are unaffected in the double-knockdown embryos. (E,F) Control (E) and Mo-nkx2.9/Mo-nkx2.2b-injected (F) embryos. There is a reduction of tal2-positive cells in the lateral floor plate (arrow) in the double-knockdown embryos. (G,H) Control (G) and Mo-nkx2.2a/Mo-nkx2.2b-injected (H) embryos. Double knockdown of nkx2.2a and nkx2.2b caused little reduction of tal2-positive cells (arrow) in the lateral floor plate. (I,J) Control (I) and triple-knockdown (J) embryos. Knockdown of all three Nkx2 genes abolished tal2-positive cells in the lateral floor plate (arrow). tal2-expressing cells (arrowhead) further dorsal in the spinal cord were unaffected in these knockdown embryos. (K) Cross-section through the trunk at hindgut extension of a triple-knockdown embryo. tal2-expressing cells in the lateral floor plate (arrow) are missing, whereas more dorsally located tal2-positive cells are present (arrowhead). Note that controls represent injections of mismatch morpholinos or combinations thereof (Table 1). Representative lateral views of the spinal cord over the hindgut extension are shown. Embryos (24 hpf) are shown with anterior left, dorsal up. Scale bar: 25 μm.
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