FIGURE 3.

Role of the lens and shh expression in Astyanax mexicanus eye degeneration. Left columns. Rescue of the cavefish eye by lens transplantation. (a) Diagram showing transplantation of a surface fish embryonic lens to a cavefish embryo (top) and a cavefish embryonic lens to a surface fish embryo (bottom). The host lenses were removed prior to transplantation. (b and c) Dissected eyes from an adult cavefish that received a surface fish lens transplant on one side as an embryo. (b) Transplant side. (c) Control side. (d and e) Dissected eyes from an adult surface fish that received a cavefish lens on one side as an embryo. (d) Transplant side. (e) Control side. Photos (b)–(e) courtesy of Yoshiyuki Yamamoto. Right columns. Role of Shh in cavefish eye degeneration. (f and g). Diagram showing expanded shhA gene expression along the embryonic midline (blue) and inhibitory effects (yellow blocked lines) on pax6 expression (red) in the optic domain of the neural plate in surface fish. (h and i) Four-gene in situ hybridization showing expanded shhA expression at the cavefish (h) midline (blue) and corresponding reduction of pax6 expression relative to surface fish (i) at the neural plate stage. No changes were seen in pax2a (blue) or dlx3 (red) gene expression. (j and k) In situ hybridization showing expanded shhA expression in the cavefish (j) compared to surface fish (k) rostrum. (l and m) Overexpression of shhA causes lens apoptosis (l, arrow) and eye degeneration (m) in surface fish. (Reprinted with permission from Ref 50. Copyright 2004 Nature Publishing Group)