Fig. 1

Fgfs Are Candidate Genes for Setting the Origin of RGC Differentiation in the Embryonic Chick Retina

(A–D) During development both Fgf3 (stage 16, [A], and arrow in [B]) and Fgf8 (stage 17, [D], and arrow in [C]) are expressed in the central retina.

(E–G) In double-staining experiments, Fgf8 expression (blue in [E], [F], and [G]) and β-tubulin (Tuj1) immunoreactivity (brown in [E], [F], and [G]) were examined shortly (stage15, [E]) before and (stage 18, [F] and [G]) after the onset of neuronal differentiation. Fgf8 expression (E) precedes and later (F and G) overlaps with the initial burst of neurogenesis (arrowheads in [F] and [G]).

(H–J) The influence of Fgf signaling on RGC differentiation was analyzed quantitatively in vitro by coculturing retinal explants with heparin beads soaked in (H) PBS, (I) Fgf8, and (J) SU5402.

(K and L) The number of islet-1-positive RGCs and phosphohistone-H3 (Ph-H3)-positive mitotic cells was determined by double immunohistochemistry. (L) Quantitative analysis from different (number indicated in brackets on each bar) experiments demonstrates that Fgf8 and SU5402 do not significantly modify the proliferation rate (Ph-H3-positive nuclei) in the explants. Note instead the dramatic effect on RGC differentiation (islet-1-positive nuclei; [K]).

ls, lens; nr, neural retina; os, optic stalk; rpe, retinal pigmented epithelium.