It is believed that cytoskeletal interactions are the motivating force behind many morphogenetic processes in the embryo. This dissertation is an investigation into certain early developmental events of the avian eye. The work is based on the hypothesis that folding of the optic vesicle to form an optic cup in the stage 13 chick requires different coordinated behaviors by cells at the margins and center of the retinal disk. An actin cytoskeleton based mechanism is proposed as the underlying cause of fold formation. The overall intent of the study is twofold: to define the role actin microfilaments play in invagination of the optic vesicle; and to propose a model for cupping of the optic vesicle that incorporates our current knowledge and the new observations.;The hypothesis has been tested by examining changes in actin filament organization in living and fixed optic vesicle cells at several pertinent time points during the process of invagination. For studies using live embryos, optocoels were injected with fluorescently labeled actin that had been covalently bound to folate (ABF). For studies using fixed tissue, ABF or BODIPY-phallacidin was injected into the optocoel. Optic vesicles were then examined by either light microscopy, confocal laser scanning microscopy, scanning electron microscopy, or transmission electron microscopy.;Time lapse video recordings were used to analyze the pattern of cell movement during optic cup formation. Processed confocal images were analyzed to determine the circumference of cell apices in various regions of the optic vesicle. Scanning electron micrographs were examined to determine overall cell shapes and sizes. Conventional thin section transmission electron microscopy was used to evaluate the degree of actin filament bundling in optic vesicles sectioned tangentially (perpendicular to the axis of the optic cup).;Results have revealed that optic cup formation is a complex interaction requiring cytoskeletal changes, coordinated with general morphological events in the rest of the developing embryo. Correct folding of the optic vesicle into an optic cup is controlled by a mechanism that may be found to be common to many developmental events involving epithelial shape changes.
展开▼
