Fig. 2. Foxn4 lies upstream of Scl in V2b interneuron development. (A) Double ISH for Scl (green) and Foxn4 (red). Confocal image of wild-type E10.5 mouse spinal cord, showing co-localisation of Scl and Foxn4 in some cells. (B-C') Sections from chicken embryos electroporated at st12-14 with ß-actin-Foxn4-IRES-GFP and analysed after a further 24 (B) or 48 (C) hours. Foxn4 does not induce Scl after 24 hours (B'). At this stage, endogenous Scl is not expressed in the chick neural tube (B'). Foxn4 does induce ectopic Scl after 48 hours (C'). (D,D') Scl expression in the p2 domain is dependant on functional Foxn4. Consecutive sections from Foxn4-null mouse embryos at E10.5 were subjected to ISH for lacZ (D) or Scl (D'). The row of Scl-positive cells visible on the left of this section are endothelial cells. (E) Scl-positive cells in a wild-type mouse embryo at E10.5. (F,G) Foxn4 expression is not dependent on Scl. Foxn4 expression was visualised by ISH at E11.5 in wild-type (F) and Scl conditional null (G) mouse spinal cords (see Materials and methods). Scale bar: 20 µm.