Working with oocyte nuclei: cytological preparations of active chromatin and nuclear bodies from amphibian germinal vesicles.

The giant nucleus or germinal vesicle (GV) of amphibian oocytes presents a remarkable opportunity to examine nuclear structures in unprecedented levels of detail. By making use of spread preparations of GVs, it is possible to investigate the structure and function of transcription units in active chromatin and a variety of nuclear bodies, all within the limits of resolution of the light microscope. The basic method for producing GV spreads that is described here is based on simple manual dissection and, therefore, it permits the preparation of nuclear components that have suffered a minimum of experimental manipulation. The particular method described is based on the use of oocytes from a salamander, the axolotl, although the approach is robust and applicable with minor modification to two other model amphibian species, Xenopus laevis and X. tropicalis. One common approach to investigating the molecular organisation of oocyte nuclear structures by immunofluorescent staining of endogenous or exogenous polypeptides is also described.