Sculpting the developing central nervous system (CNS) requires the intricate coordination of concurrent, sometimes opposing, events. This development is highly regulated by growth factors. Progress in our laboratory over the last five years has shown (a) that ethanol-induced damage to proliferating populations is temporally and spatially defined and that mitogenic and anti-mitogenic growth factors are uniquely affected by ethanol. A pivotal growth factor in CNS development is transforming growth factor beta1 (TGFbeta1); it affects multiple processes including cell proliferation, migration, survival, and neurite outgrowth. We will focus on two contiguous developmental events, cell proliferation and migration. Intriguingly, TGFbeta1 affects these events in opposite ways; it inhibits cell proliferation and promotes neuronal migration. Ethanol affects both events in a developmental state- and cell-dependent manner. Based on this understanding, we pose three hypotheses. (1) Ethanol affects the TGFbeta1-mediated transition of cells moving from the proliferative population to the migratory population. (2) Ethanol interferes with the secretion of TGFbeta1. (3) Ethanol affects TGFbeta1-regulated activities through the expression and function of its receptors. Each hypothesis will be tested using structural and functional assays.
Three Specific Aims are to determine the effects of ethanol (1) on TGFbeta1-regulated cell cycle kinetics, the proportion of cells that leave the proliferative population, and the kinetics of neuronal migration, (2) on TGFbeta1availability (the expression of latent and active forms of TGFbeta1, and the expression and stability of ligand transcript), and (3) on the expression of TGF(1 receptors in ectopic cells, the affinity and density of TGFbeta1 receptors and receptor phosphorylation in proliferating and migrating cells in situ. These studies will be performed using molecular and cell biology methods and bioassays on two types of culture models: organotypic slice cultures of fetal cerebral cortex and dissociated cell cultures (cortical neurons, astrocytes and neural cell lines). In summary, the proposed studies will explore mechanisms that explain much of the damage associated with alcohol related neurological defects and provide new insights into TGFbeta1-mediated cell proliferation and neuronal migration.
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