A role for gp210 in mitotic nuclear-envelope breakdown.

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• During mitosis, the nuclear envelope (NE) disassembles, allowing cytoplasmic and nuclear mixing.
• Nuclear pore complexes (NPCs) and the nuclear lamina are key components of the NE that disperse during NE breakdown (NEBD).
• gp210 is a single-pass transmembrane glycoprotein found in metazoan NPCs, but its role in NEBD is not fully understood.

Purpose of the Study:

• To investigate the function of gp210 in nuclear envelope breakdown (NEBD) during mitosis.
• To determine the role of gp210 phosphorylation in NEBD and associated processes.
• To elucidate the molecular mechanisms underlying NEBD and its regulation.

Main Methods:

• RNA interference (RNAi)-mediated depletion and mutation of gp210 in Caenorhabditis elegans embryos.
• In vitro assays using antibodies against gp210 to block NEBD.
• Analysis of lamin depolymerization, chromosome alignment, and segregation.
• Depletion of cyclin B in C. elegans embryos.

Main Results:

• Depletion or mutation of gp210 in C. elegans embryos impaired NEBD, preventing lamin depolymerization and causing twinned nuclei.
• Antibodies targeting the gp210 cytoplasmic tail blocked in vitro NEBD and inhibited gp210 hyper-phosphorylation.
• gp210 phosphorylation, potentially mediated by cyclin-B-cdc2, appears crucial for NEBD.
• Cyclin B depletion also resulted in a nuclear-twinning phenotype.

Conclusions:

• gp210 is essential for efficient NPC disassembly and NEBD.
• Phosphorylation of gp210 is an early, critical event in NEBD, required for lamin disassembly.
• gp210 plays a vital role in regulating mitotic nuclear envelope dynamics and ensuring proper chromosome segregation.