Lens fibre cell differentiation - A link with apoptosis?

During the process of terminal differentiation, the fibre cells in the eye lens undergo many changes that are reminiscent of apoptotic/necrotic change s. Mitochondria, for instance, undergo permeability transition and nuclear degradation is accompanied by chromatin condensation, disintegration of the nucleolus, dissolution of the nuclear lamina, nuclear pore clustering and fragmentation of the DNA into oligonucleosomal fragments. As during apoptos is, members of the caspase family of proteases were shown to be active duri ng fibre cell differentiation and Bcl-2 overexpression was demonstrated to block normal differentiation of lens cells. In this review, the current kno wledge of the sequence of events during cell death is summarised and contra sted with events during lens fibre cell differentiation. Due to the numerou s similarities between these processes, lens fibre cell differentiation is suggested to represent an attenuated form of cell death.