Nuclear envelope rupture in Drosophila D11 cells inhibits mitosis

Snezhanna Sergeevna Saydakova¹, Ksenia Nikolaevna Morozova², Elena Vladimirovna Kiseleva³, Gera Alekseevna Pavlova⁴
¹ICG SB RAS, NSU, custodian.of.midnight@gmail.com
²ICG SB RAS, morozko@bionet.nsc.ru
³ICG SB RAS, elka@bionet.nsc.ru
⁴IMCB SB RAS, gera.pavlova@mcb.nsc.ru

It is already known that lesions in the organization of the nuclear envelope (NE) negatively affects the stability of the genome functioning, transport of molecules between the nucleus and the cytoplasm, as well as the process of cell division. In previous studies we demonstrated the atypical interaction of ER membranes with the outer nuclear membrane (ONM) at the prometaphase stage, leading to the formation of 4-layered membranes and a disassembly delay of the NE. Our current study is focused on the ultrastructural organization of Drosophila D11 cells, which shows a significant decrease in the number of dividing cells. Our TEM analysis demonstrated that the nuclei of many cells contain numerous microtubules in the nucleoplasm, slightly compacted chromosomes and an atypical NE with extended folds and outgrowths shaped like 4-layered membranes. These structures represent membrane complexes consisting of inner nuclear membranes (INM) layers close attached to each other. The formation of multilayer fragments from adherent outgrowths of the NE was previously observed when the lamina protein Lam or the insect-specific protein KUGELKERN was overexpressed. According to these data we suggest that the low mitotic index of Drosophila D11 cells division is associated with misregulation of the mitosis process, possibly due to imbalance in the expression of genes encoding lamina proteins, which stimulates the synthesis and elongation of the nuclear membrane without disassembling it. Excessive NE membranes form loops and folds protruding to the cytoplasm and sticking together due to mutual fusion of the INMs forming the quadruple structures.