The ciliary body secretes an aqueous fluid that bathes the anterior eye and is involved in maintaining intraocular pressure. Increased pressure in the mature eye is a major risk factor for glaucoma, a leading cause of blindness. Conversely, during development , insufficient fluid production is thought to cause microphthalmia. The ciliary body and iris have been identified as containing resident retinal neural stem cells. Despite its essential functions, little is known about the development of the ciliary body. The ciliary body is first identifiable at the anterior margin of the optic cup where the neuroepithelium folds back on itself, forming an epithelial lip. Thus, the ciliary body is found at the boundary between two discrete eye tissues: the pigmented epithelium and the neural retina. Our previous work has shown that ciliary body tissue can be induced by re-creating discrete borders between FGF-induced ectopic neural retina and pigmented epithelium. When ectopic borders are induced in the front of the eye, optic cup-like invaginations are formed. The lips of both the ectopic invaginations and the native optic cup express CollagenIX, a definitive marker for ciliary body, and Wnt2b. Preliminary data presented here provide evidence that the basic patterning of the eye occurs at the optic vesicle stages and that the pattern is carried through morphogenesis. The following hypotheses will be tested: 1) Anterior optic cup fate is pre-patterned in the optic vesicle. 2) Wnt2b is involved in the morphogenesis of the optic cup from the optic vesicle. 3) Prepatterning of the optic vesicle restricts ectopic induction of invagination to the anterior optic cup. The first hypothesis will be tested by examining ectopic anterior eye marker expression at the boundaries between growth factor induced zones of neural retinal tissue compared to zones of cell autonomous induction of neural retina (Aim 1). Second, the role of Wnt signaling in the invagination of the optic cup will be tested by using retroviruses to ectopically express both canonical and non-canonical Wnt ligands. The resultant eyes will be examined for ectopic invaginations and changes in morphology at a cellular level (Aim 2). Finally, the restricted occurrence of ectopic invaginations will be studied by targeting specific areas and ages of optic vesicle with FGF to induce ectopic neural retina within the pigmented epithelium. Ectopic borders will be examined for invaginations and anterior eye marker expression (Aim 3). This study will provide a better understanding of key events in the early development of the anterior eye, thus linking morphogenetic and genetic information that may help develop treatments for eye diseases such as micropthalmia, glaucoma, and coloboma.
Anterior segment dysgenesis, microphthalmia, coloboma and other defects of development are associated with overall genetic syndromes and with environmental factors. This proposal seeks to provide better basic understanding of early eye development, particularly of the anterior portion of the eye, and to link genetic information with morphological processes.
