The Function Of Apical Polarity Complexes On Cellular Migration And Organization Of Zebrafish Lens

Purpose:The lens is a key component of refractive media,which,focuses incoming light onto the retina and form clear vision by adjustment.The mature ocular lens is a specialized transparent optical element composed of two types of cells lined in coordinated manner including an outer single cuboidal epithelial layer covering elongated fiber cells.The correct pattern of cellular organization and migration during development can account for the formation of refractile,symmetric and biological lens,which can develop deformities by disordered cellular organization and arrangement,thus causing decreased vision or even blindness.Cell polarity is involved in multiple biological processes including embryonic development,cellular migration and epithelial-mesenchymal transition(EMT)as well as maintance of tissue architecture.Recent studies have revealed vital function of cell polarity in cellular adhesion,organization and migration.During lens development,polarity is established and maintained along apical-basal axis of epithelial cells and the location and interaction of components of numerous well-conserved polarity complexes including PAR,Crumbs and SCRIB participated in this process.Exact cellular localization,adhering junctions and migration are crucial for normal lens function,however,the exact role of cell polarity in lens development remains to be discovered.Based on the above background,the present study used the zebrafish as experimental model organism and systematically analyzed the function of apical polarity complexes including Crb(crumbs)and Par(partitioning defective)complexes in cellular adhension,migration and differentiation during lens development.Methods:We use AB wildtype and apical polarity complexes Crb2a m289、αPKCλ m567、Pard6gb fh266 zebrafish as model organism to explore the localization,expression sequence and dynamic dependency relation of Crb and Par complexes during lens development and their critical influence on cell aghension,differentiation,subcellualr location and recombination of adhesion molecules,as well as cellular migration and organization via stereomicroscope photography,frozen section and immunohistochemistry(IHC),and high-resolution transmission electron microscopy(TEM).The influence of polarity complexes on ocular and lens size as well as numbers of epithelial cells and fiber cell nuclei was quantitatively analyzed through statistical approach.We also explored the different expression and cellular organization patterns of the two polarity complexes between mammalian and vertebrates during early lens development using wild type mice as model organism via IHC.Results:Our study revealed that the early development of zebrafish lens starts with the expression of Par complex in non-polar distribution,followed by the expression of Crb complex which induced cell polarity in the lens.Destroyed complexes would influence ocular and lens development and the organization pattern of epithelial and fiber cells as well as leading to the early entry of cells in germinative zone into transitional zone,while there was no obvious change in lens differentiation.The results of IHC and TEM show that polarity disorganization resulted in abnormal cellular migration through affecting adhesion of the cells,thereby promoting disintegration of adhesion and mobility of cells.Our study revealed for the first time the complex dynamic regulating relation of the two complexes in different status of lens cells which break through the common understanding of simple positive correlation of the two complexes.Furthermore,we confirmed that the Crb complex was involved in the ordered migration pattern of cells around the center of lens during early development in different species.Conclusions:The present study established model of polarity disorganization on zebrafish and systematically revealed the distinct function of Par and Crb complexes in zabrafish lens development as well as the dynamic modulation between the two complexes for the first time,the former induced the early formation of cell adhesion,while the latter mediated the micro-subcellular localization.The two complexes work in coordinated manner to modulate the migration and organization of two types of lens cells.Our study established a doog experimental model to further study the mechanism of lens development and also lays a foundation for further study on the mechanism of lens diseases.