IBN-9507979 Nordeen, Ernest J. Understanding how the production, specification and survival of nerve cells are regulated to generate variation in neuron number is an important goal of developmental neurobiology. In many instances, these processes are influenced by steroid hormones such as estrogen, which act on the developing nervous system to regulate neuron number and growth within specific brain regions. This proposal concerns the biological mechanisms and cellular populations through which these hormones exert control over brain cell number. Several proposed studies will test the hypothesis that hormones prevent cell death to influence neuron number within specific brain regions. Other studies are aimed at identifying the cell populations actually mediating these neurotrophic effects of steroids. More specifically, experiments will test the notion that some neurons transiently express estrogen receptors during their migration, and depend on this hormone for their survival during this period. In addition, the work will address how glia contribute to the neurotrophic effects of steroid hormones during development. The long term aim of these studies is to use the hormonal regulation of neuron growth and survival as a tool with which to explore the underlying cellular and molecular changes influencing a neuron's decision to live or die. In so doing, a greater understanding of the factors contributing to neuron death during development and in disease will be attained.
