Identification of a novel intercellular structure in late-stage differentiating lens cells

This study describes a novel intercellular structure in the adult bovine lens. In differential interference contrast images, the structure has the shape of a thickened torus or 'bagel' of 3-9 μm in diameter and is contributed equally by 2 adjacent fibre cells. Due to its shape and location reaching into 2 neighbouring cells, the novel structure was termed 'intercellular torus' or 'bagel'. Intercellular bagels are present in a subset of late-stage lens fibre cells of the intermediate cortex, a considerable time after the cytoplasmic organelles have been broken down and the pyknotic nuclear remnants have disappeared. They are not present in deeper fibres. Our experiments show that intercellular bagels do not stain positive for DNA or RNAs, but are rich in lipids. Preliminary data indicate that the intercellular bagels contain calcium, suggesting that they might act as a place of transient Ca²⁺ storage or sequestration after the intracellular organelles, such as the endoplasmatic reticulum, nuclear envelope, Golgi apparatus and mitochondria have been eliminated from the lens fibres during terminal differentiation.