Effects of cold shock treatment on amphibian oocytes: alteration of heterogenous nuclear RNP morphology

In cold-stressed oocytes of Pleurodeles waltl, lampbrush chromosome lateral loops exhibited important structural modifications which were visualized under light microscopy. Electron microscopy study revealed that the RNP particles associated with growing transcripts in the matrix of these loops were 15 nm at 8°C compared to 30 nm at normal temperature (20°C); hnRNP isolated from cold-stressed oocytes sedimented at 15 S in sucrose, while those from control oocytes sedimented at 30 S, as expected. However, under both normal and cold stress conditions, hnRNP possessed a buoyant density of 1.38 g/cm3 in CsCl, indicating that their typical RNA/protein ratio was maintained at 8°C. Our results demonstrate that cold stress affects the structure of hnRNP in amphibian oocytes.