Over the years, researchers studying the nucleus have got tantalising glimpses of filamentous structures emanating from the nuclear pore complexes (NPCs) into the nucleus. But imaging the inside of the nucleus is technically difficult, not least because the chromosomes tend to obscure all other structures. Now, on , Elena Kiseleva, Katherine Wilson and colleagues use field emission scanning electron microscopy to probe the nucleus of a 3-4 stage Xenopus oocyte, which contains proportionally little chromatin. The authors' stunning images reveal a complex network of 12–100-nm diameter structures attached to the NPCs and extending throughout the nucleus. These pore-linked filaments (PLFs) are embedded into spherical structures 100 nm to 5 mm in diameter, some of which the authors identify as Cajal bodies by immunogold staining. Other experiments indicate that the PLFs contain actin and protein 4.1, an actin-scaffolding protein. Given these results, the authors propose that PLFs could both provide tracks for intranuclear trafficking and be involved in the creation and maintenance of chromatin-free diffusion channels below each NPC.
