EN
PML is a tumor-suppresor protein involved in the pathogenesis of promyelocytic leukemia. In proliferating mammalian cells PML is a principal component of characteristic nuclear bodies, which contain other proteins but do not contain nucleic acids. There are several PML bodies per nucleus. The molecular function of PML protein is unclear, yet the majority of data points to its involvement in regulation of gene-expression and/or intranuclear protein storage and degradation. In the brain PML has been implicated in the pathogenesis of neurodegenerative disorders, glioma and in the control of embryonic neurogenesis. It is not clear whether the protein is expressed, and has a function, in the normal adult brain. Therefore we have investigated the expression and localization of PML at the cellular and subcellular levels, in the adult mouse brain. By immunofluorescence, typical PML bodies were found in a subset of neurons in the cerebral cortex, hippocampus and amygdala. In the cortex, the protein was present predominantly in layer II/III. Stimulation of neuronal activity by a) pentylenetetrazole seizures or b) immobilization stress, greatly increased the size and signal-intensity of the neuronal PML bodies. Our results suggest that function of PML protein in the brain can be associated with neuronal activity and plasticity.