Abstract
Purpose :
The removal of lens organelles from lens fiber cells is critical for lens clarity. Multiple congenital cataract models show retention of nuclei in the purported organelle free zone, indicating that nuclear breakdown is among essential processes in establishing and maintaining lens clarity. Documentation of processes involved in nuclear envelope breakdown is limited. Identifying the steps of nuclear envelope breakdown in lens denucleation may provide insight into mechanisms of cataract development.
Methods :
Nuclear morphology and localization of nuclear Lamins, nuclear pore complexes and inner and outer nuclear membrane proteins were examined during differentiation in chick and mouse lenses using immunofluorescence. Nuclear structure was examined in WT mice using electron microscopy.
Results :
Phosphorylation of Lamin is associated with nuclear envelope breakdown. In chick lenses, phosphorylation of Lamin A immediately precedes nuclear condensation. Additionally, after Lamin phosphorylation, nuclear Lamin staining becomes discontinuous in the nuclear membrane. The nuclear pore complex also becomes discontinuous in the nuclear membrane after Lamin phosphorylation and no longer localizes with Lamins. Analysis of nuclear membrane structure by electron microscopy shows nuclear envelope breakdown in areas devoid of nuclear pore complexes.
Conclusions :
These data suggest that as in mammalian lenses, phosphorylation of Lamin is an important step in nuclear envelope breakdown during lens fiber cell denucleation in the chick. Furthermore, reorganization of nuclear membrane proteins precedes denucleation.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.