F-Spondin Expression in Zebrafish Figure 7. Spon1b expression in the hypothalamic area. A. Ventral view of a freshly-dissected adult Tg(spon1b-GFP) brain: fluorescence signal in the ventral (Hv) and caudal (Hc) hypothalamic nuclei, the tectobulbar tract (TTB), the interpeduncular nucleus and superior raphe (asterisk), and fibers from the fasciculus retroflexus (FR). B. Coronal section at the level of the ventral hypothalamus (Hv), immunostained for GFP. Note the strong fluorescence signal in FR and medial longitudinal fasciculus (MLF), but its absence in the horizontal commissure (Chor) and lateral lemniscus (LLF). Optic tectum (TeO), posterior tuberal nucleus (PTN), paraventricular nucleus (PVO), torus longitudinalis (TL), valvula cerebelli (Val). C. Spon1b expression in periventricular cells (arrowheads) of the Hv nucleus (boxed area in B) with long projections extending laterally (arrows). D. Coronal section at the level of the caudal hypothalamus (Hc) showing high spon1b expression in the nucleus of the posterior recess (NPR), and long projections within the dorsal hypothalamus (asterisk). These projections, in part, originate from the most lateral cells of the NPR (arrow in inset). Note strong signal in scattered cells and projections in the tegmentum (arrows), ansulate commissure (Cans), and tectobulbar tract (TTB). E. Robust spon1b expression in the NPR. Note the dorsal projections of CSF-contacting neurons. F. Cells in NPR showing co-localization of the pan-neuronal marker Hu PLoS ONE | www.plosone.org 11 June 2012 | Volume 7 | Issue 6 | e37593