An enhanced expression of the immediate early gene, Egr-1, is associated with neuronal apoptosis in culture

• Published in: Neuroscience 1999-01, Vol.91 (4), p.1529-1538
• Main Authors: Catania, M.V., Copani, A., Calogero, A., Ragonese, G.I., Condorelli, D.F., Nicoletti, F.
• Format: Article
• Language: English
• Subjects: Ageing, cell death; Animals; Animals, Newborn - metabolism; apoptosis; Apoptosis - physiology; Biological and medical sciences; Cell physiology; Cells, Cultured; Cellular Senescence - physiology; Cerebellum - cytology; Cerebellum - physiology; Culture Media - pharmacology; cultured granule cells; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Early Growth Response Protein 1; Egr-1; Egr-1 protein; Fos; Fundamental and applied biological sciences. Psychology; GABAergic neurons; Gene Expression - physiology; Genes, Immediate-Early - genetics; immediate early genes; Immediate-Early Proteins; Molecular and cellular biology; Neurons - physiology; Proto-Oncogene Proteins c-fos - metabolism; Rats; Rats, Sprague-Dawley; Transcription Factors - genetics; Transcription Factors - metabolism
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/S0306-4522(98)00544-2

Cultured cerebellar granule cells grown in medium containing 10 mM K + (K10) underwent apoptosis after four to five days in vitro, unless they were rescued by the addition of insulin-like growth factor-I. The few GABAergic neurons present in the cultures were more resistant to apoptotic degeneration, as indicated by double fluorescent staining with the chromatin dye Hoechst 33258 and with glutamate decarboxylase-67 antibodies. As compared with sister cultures grown in 25 mM K +, K10 cultures showed an increased expression of the Egr-1 protein and a reduced expression of the Fos protein. The increase in Egr-1 was more substantial in granule cells than in GABAergic neurons, and was not oberved in K10 cultures chronically exposed to insulin-like growth factor-I. To examine the temporal relationship between the increase in Egr-1 and the development of programmed cell death, we induced apoptosis in K25 cultures at six days in vitro by replacing their medium with serum-free K10 medium. A substantial, but transient, increase in Egr-1 expression was observed in granule cells 6 h after switching the medium, a time that preceded the appearance of the phoenotypical markers of apoptotic death. An early reduction in the Fos protein was observed after switching the medium from K25 into serum-free K10, but also after switching the medium into serum-free K25, a condition which was not associated with the development of apoptosis nor with the increase in Egr-1. We suggest that a transient induction of Egr-1 contributes to the chain of events leading to the execution phase of neuronal apoptosis in culture.