FUNCTION AND EXPRESSION OF THE BCL-X GENE IN THE DEVELOPING AND ADULTNERVOUS-SYSTEM

WE have shown that overexpression of Bcl-x can rescue sympathetic neur ones from nerve growth factor deprivation in vitro. We have also exami ned the distribution and expression of Bcl-x mRNA in the developing an d adult nervous system using Northern blot and in situ hybridization. Bcl-x mRNA is widespread during development of the nervous system. In embryonic spinal cord, mRNA levels increase at the beginning of the na turally occurring cell death period, suggesting that Bcl-x may be invo lved in the selection of neurones during this period. In the brain, Bc l-x expression increases after birth to reach a high level in the adul t brain. Neurones from the cortex, olfactory bulb, and Purkinje cells are among those expressing the highest levels of Bcl-x mRNA. The wides pread expression of Bcl-x during development and in adult brain sugges ts of a role for Bcl-x beyond simply protecting neurones from developm ental cell death.