Morphological Changes and Nuclear Pore Clustering during Nuclear Degradation in Differentiating Bovine Lens Fibre Cells

The programmed degradation of organelles is a characteristic feature of lens fibre cell differentiation. Due to the large number of similarities between the programmed organelle loss during lens development and the changes to organelles in apoptosis, lens cell differentiation has been suggested to share a common basis with programmed cell death. This study was aimed at characterising the morphological changes to the nucleus during cellular differentiation in the bovine lens at the ultrastructural level. Progressive shrinkage of the nucleus is accompanied by clumping and marginalisation of the chromatin to the nuclear periphery. Additionally, the fate of another key component of the nuclear envelope – the nuclear pore complexes – was followed. In parallel to the shrinkage of the nucleus, the nuclear pores progressively cluster into large aggregates that associate with the condensed DNA. These observations in differentiating lens fibres mirror the situation in cells undergoing apoptosis and thus provide additional data supporting a common basis between the two processes.