||F/g~re 5. Kv2.2 mRNA localizes to the ventral spinal cord and perinuclcar somite regions during development of excitability. These views are obtained
from 30 pm sections of whole-mount embryos that were hybridized to a Kv2.2 antisense probe. Sections were counterstained with methyl green, which
intensely colors nuclei. Dorsal is UP in all panels. In the sagittal sections, rostra1 1s to the r&zt. A, In a cross-section from a stage 23 embryo, Kv2.2 mRNA
is restricted to the ventrolateral portion of the neural tube (open u~.rdws) and region around the somite nuclei (filled arrowhead). B, A sense control stage
23 embryo is observed in cross-section; the color is attributable solely to methyl green countcrstaining. Sense controls for other stages and planes of section
provide similar results. C, At stage 26, the signal in the ventral portion of the neural tube (open arrowheads) resembles the pattern observed at stage 23
(A). In the somitcs, the signal predominates around nuclei @Ned arrowheads). D, In a parasagittal section of a stage 26 embryo, the Kv2.2 hybridization
signal concentrates around the somite nuclei. E, In a sagittal section of a stage 26 embryo, the Kv2.2 hybridization signal concentrates in the ventral region
of the neural tube in discrete patches. The Kv2.2 signal delimits the ventral extent of the neural tube, whereas the nf is positioned within the dorsal region.
F, G, Sections obtained from stage 35 embryos probed with either anti,cnse Kv2.2 (F) or Kvl.1 (G) probes. The black varicosities surrounding the spinal
cord (durk thzn avowheuds) are attributable to pigmented cells found in the embryos used for this experiment, which were caused by the mating of an
albino female and a pigmented malt. By stage 35, pigment begins to appear in albino/pigmented embryos. F, By stage 35, Kv2.2 expression in the neural
tube (open arrowheud,) appears fainter than at stage 23 (C), which is consistent with what is observed at the whole-mount level (Fig. 4F). G, Kvl.1 mRNA
localizes to the dorsal region of the spinal cord indicated by the open arowa. Scale bar (shown in A): A, 50 pm; R, 75 km; C, 100 km; D, 100 Km; E, 200
km; F, 100 pm; G, 100 pm. Abbreviations: nt, neural tube (spinal cord); 5, somites; /zot, notochord.