The lens consists of a monolayer of epithelial cells that overlies fibre cells that differentiate from epithelial cells at the equator. While developing, fibre cells need mitochondria to provide energy, as they mature they lose these and other organelles to increase transparency and passage of light. Lens epithelial cells maintain mitochondria and supply nutrients and maintain lens homeostasis. Proteosomal and DNA degradation have been shown to have a role to play in organelle loss in fibre cells, but these are not the only mechanisms. Autophagy is a process whether cellular proteins and organelles can be enclosed in phagolysosomes leading to destruction. Degradation of mitochondria specifically is termed mitophagy. Whether autophagy is involved in organelle degradation in the lens is unclear with reports both supporting and refuting this mechanism. In this study, Costello et al. used electron microscopy and dual-label confocal microscopy to demonstrate the presence of autophagic vesicles containing mitochondria in lens epithelial and fibre cells. In support of this serum starvation, a common protocol to induced autophagy, led to mitophagy in primary lens epithelial cells. To date, loss of crystalline activity in clearance of aggregated proteins has been linked to cataract development. Now the autophagy pathway should be included in future studies.

Autophagy and mitophagy participate in lens organelle degradation.
Costello MJ, Brennan LA, Basu S, et al.
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Graham Wallace

Birmingham and Midland Eye Centre, Birmingham, UK.

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