Nuclear membranes and nuclear pore complexes (NPCs) are conserved in both animals and plants. However, the lamina composition and the dimensions of NPCs vary between plants, yeast, and vertebrates. In this study, we established a protocol that preserves the structure of Caenorhabditis elegans embryonic cells for high-resolution studies with thin-section transmission electron microscopy (TEM). We show that the NPCs are bigger in C. elegans embryos than in yeast, with dimensions similar to those in higher eukaryotes. We also localized the C. elegans nuclear envelope proteins Ce-lamin and Ce-emerin by pre-embedding gold labeling immunoelectron microscopy. Both proteins are present at or near the inner nuclear membrane. A fraction of Ce-lamin, but not Ce-emerin, is present in the nuclear interior. Removing the nuclear membranes leaves both Ce-lamin and Ce-emerin associated with the chromatin. Eliminating the single lamin protein caused cell death as visualized by characteristic changes in nuclear architecture including condensation of chromatin, clustering of NPCs, membrane blebbing, and the presence of vesicles inside the nucleus. Taken together, these results show evolutionarily conserved protein localization, interactions, and functions of the C. elegans nuclear envelope.
Bibliographical noteFunding Information:
We are grateful to Ueli Aebi and Terry Allen for stimulating discussions and for providing dimensions for the NPC (Ueli Aebi and Terry Allen) and perinuclear space (Ueli Aebi). This work was supported by grants from the USA–Israel Binational Science Foundation (BSF), the Israel Science Foundation (ISF), the German–Israel Foundation (GIF 1-573-036.13), and the Austrian Bank (to Y.G.), the National Institutes of Health (GM64535 to K.L.W.), and the Journal of Cell Science for a travel allowance (M.C.).
- Electron microscopy
- Nuclear envelope
- Nuclear lamina
- Nuclear pore complexes