Fig. 4

Localization of Zash-1a transcripts in the wild-type 24-hr CNS. Thick sections of whole mount in situ hybridized embryos (as in Fig. 3) were observed and photographed under DIC optics. (A) Longitudinal section of head showing region from anterior tip of head to cerebellum (eye and lateral head removed). (B) Longitudinal section of hindbrain extending from cerebellum to rhombomere 7. Symbols: arrowheads, approximate rhombomere borders; open arrow, transcripts in ventral region of rhombomere 1. Outline of otocyst is shown as dotted line. (C) Transverse section of anterior midbrain. (D-F) Transverse sections of rhombomeres 1, 4, and 7, respectively. Symbols: arrowheads, transcripts in cells at border between basal and alar plates; open arrows, as in (B). (G) Transverse section of midtrunk spinal cord, open triangles, transcripts in cells near floor plate. Planes of transverse sections (C-F) are indicated by the double-headed arrows in (A) and (B). Plane of transverse section in Fig. 9A is indicated in (A) by a double-headed arrow without an accompanying letter. Abbreviations (in addition to those used in Fig. 3): a, alar plate; drc, dorsorostral cluster; E, eye; F, floor plate; n, notochord; p, pituitary; s, spinal cord; so, somite; vec, ventrocaudal cluster; vrc, ventrorostral cluster; [dorsorostral, ventrocaudal, and ventrorostral clusters are the positions of early acetylcholinesterase-expressing cells in the telencephalon and diencephalons (Ross et al., 1993)]. Scale bars, 100 μm; magnification of (A-C) is identical, and that of (D-G) is identical.