| Summary: | 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
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