Identification of the laminar-inducing factor: Wnt-signal from the anterior rim induces correct laminar formation of the neural retina in vitro.
To study the molecular mechanism that controls the laminar organization of the retina, we utilized reaggregation cultures of dissociated retinal cells prepared from chicken embryos. These cells cannot generate laminated structures by themselves and, instead, form rosettes within the reaggregates. However, the dissociated cells can organize into a correctly laminated structure when cultured in the presence of a putative laminar inducing factor coming from particular tissue or cells, but its molecular identity of this factor has long remained elusive. In this study, we found that the anterior rim of the retina sends a signal to rearrange the rosette-forming cells into a neuroepithelial structure characteristic of the undifferentiated retinal layer. This activity of the anterior rim was mimicked by Wnt-2b expressed in this tissue, and was neutralized by a soluble form of Frizzled, which works as a Wnt antagonist. Furthermore, the neuroepithelial structure induced by Wnt-2b subsequently developed into correctly laminated retinal layers. These observations suggest that the anterior rim functions as a layer-organizing center in the retina, by producing Wnt-2b.
Nakagawa
Shinichi
S
RIKEN Center for Developmental Biology, 2-2-3 Minatojima Minamimachi, Chuo-ku, Kobe 650-0047, Japan. nakagawa@cdb.riken.go.jp
Takada
Shinji
S
Takada
Ritsuko
R
Takeichi
Masatoshi
M
D000818:Animals; D030161:Avian Proteins; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002642:Chick Embryo; D017077:Culture Media, Conditioned; D004627:Embryonic Induction; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism; D051157:Frizzled Receptors; D018507:Gene Expression Regulation, Developmental; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000196:embryology; D011518:Proto-Oncogene Proteins / Q000378:metabolism* / Q000494:pharmacology; D012160:Retina / Q000166:cytology / Q000187:drug effects / Q000196:embryology* / Q000378:metabolism*; D051154:Wnt2 Protein; D029867:Xenopus Proteins
D030161:Avian Proteins; D017077:Culture Media, Conditioned; D005136:Eye Proteins; D051157:Frizzled Receptors; D011518:Proto-Oncogene Proteins; C424042:Wnt-2b protein, Gallus gallus; D051154:Wnt2 Protein; D029867:Xenopus Proteins; C432154:fzd5 protein, Xenopus