Loss of adenomatous polyposis coli ( apc ) results in an expanded ciliary marginal zone in the zebrafish eye

The distal region of neural retina (ciliary marginal zone [CMZ]) contains stem cells that produce non‐neural and neuronal progenitors. We provide a detailed gene expression analysis of the eyes of apc mutant zebrafish where the Wnt/β‐catenin pathway is constitutively active. Wnt/β‐catenin signaling leads to an expansion of the CMZ accompanied by a central shift of the retinal identity gene sox2 and the proneural gene atoh7 . This suggests an important role for peripheral Wnt/β‐catenin signaling in regulating the expression and localization of neurogenic genes in the central retina. Retinal identity genes rx1 and vsx2 , as well as meis1 and pax6a act upstream of Wnt/β‐catenin pathway activation. Peripheral cells that likely contain stem cells can be identified by the expression of follistatin , otx1 , and axin2 and the lack of expression of myca and cyclinD1 . Our results introduce the zebrafish apc mutation as a new model to study signaling pathways regulating the CMZ. Developmental Dynamics 239:2066–2077, 2010. © 2010 Wiley‐Liss, Inc.