Morphological investigations into the development of the mammalian corneal endothelium using the mouse model

Doctoral Thesis


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University of Cape Town

The corneal endothelium (CE), a mesenchyme-derived tissue, is a monolayer of squamous cells on the inner corneal surface. In Foxc1-1• mice, the CE fails to form. The understanding of the cause of this defect has implications for the study of human eye disorders that are related to FOXC1 mutations. To understand the basis of CE defects in Foxc1-1- mice, an analysis of normal CE development was performed using scanning electron microscopy. Results showed that in normal mice the transformation from mesenchyme to endothelium was initiated at embryonic day (E) 12.5 and was characterised by a change from stellate to cobblestone shape and the formation of junctions. In FoxcN- mice, the process was initiated but a cobblestone shape not attained. The expression of adherens (N-cadherin) and tight junction (Z0-1) proteins was investigated by immunoflouresence microscopy. In the normal embryo, the expression of N-cadherin was initially in cytoplasmic vesicles and later at the cell membranes. ZO-l was first detected at the cell peripheries at E13.5. In Foxct-I- mice, N-cadherin peripheral bands failed to form. ZO-l was not expressed. These results suggest that the failure to form a monolayered CE in Foxc1 mice is due to incomplete mesenchyme-endothelial conversion. Junction formation was further investigated in vitro. N-cadherin was cytoplasmic in pre-confluent cells and at cell edges in confluent cells. ZO-l was not detected. These results suggest that in vitro, these cells are either unable to form tight junctions or the culture medium does not contain the appropriate signalling molecules.

Includes bibliographical references (leaves 83-89).