Role of B integrins in the early differentiation of the RPE and neural retina in the chicken embryo

• Main Author: Iagallo, Michael Charles Anthony
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/8156

The early differentiation of the retina and retinal pigment epithelium (RPE) of the chicken embryo involves a complex series of morphological changes and cell migrations. The interactions of extracellular matrix (ECM) molecules, cell adhesion molecules such as P, integrins, and soluble growth factors are believed to mediate this process. The temporal and spatial distribution of ECM molecules laminin and fibronectin and the integrin subunits β₁, α₃,α₄, α₅, α₆, andα, was determined by immunohistochemistry in the chicken embryo between stage 8 (E2) and stage 24 (E4). Laminin and fibronectin were present in basement membranes throughout the stages examined, and intracellular fibronectin was observed in stages 8 through 24. Fibronectin staining in ganglion cells at stages 22-23 is reported for the first time. A pericellular staining pattern was observed for β₁ integrin subunit at all stages examined. Alpha 3, α₄, α₅, and α₆ integrins showed a polarized distribution in the RPE postoptic cup formation. Alpha v integrin displayed a diffuse, vesicular staining pattern throughout the stages examined except for a distinctive zipper-like staining pattern at the RPE-NR interface. This pattern is possibly an indication of cell-cell interactions between the neuroblasts of the outer NR and the RPE. Alpha 3 integrin appeared to be heavily expressed in the differentiating RPE, and in the early migrating neuroblasts. The distribution of α₄ integrin is mainly in ectodermal structures before optic cup formation, but became more widespread within the NR and especially in the RPE basement membrane. The α₅ integrin distribution indicated a role in early differentiation of lens fibres and ganglion cells. Alpha 6 was only expressed in the post-optic cup retina. This distribution suggests a role in later developmental events such as neurite extension and maintenance of differentiated phenotype. The distribution of β₁ and a integrin subunits with respect to morphological changes observed during retina development point to a significant role of integrin-ECM interactions