OREGON HEALTH & SCIENCE UNIVERSITY
This is a revised renewal application aimed at elucidating the neuroendocrine mechanisms underlying the initiation of female puberty. During the last funding period we examined the hypothesis that the activation of LHRH secretion at puberty requires a cell-cell communication process provided by structurally and functionally connected neuronal and glial subsets of the hypothalamus. We also began testing the hypothesis that neuron-glia bidirectional communication, and hence the pubertal process itself, is under the transcriptional control of "upstream" regulatory genes. We established the initial framework supporting both concepts by: a) defining erbB-1 and erbB-4 tyrosine kinase receptors as major components of the communication pathway used by glial cells to facilitate LHRH release, b) identifying ionotropic/metabotropic receptors as signaling molecules used by glutamatergic neurons to coordinate the facilitatory transsynaptic and glial input to LHRH neurons, and c) defining the homeodomain gene TTF-1 as an example of an upstream hierarchy of genes involved in the transcriptional control of puberty. In addition to accomplishing these goals we identified two new components of the cell-cell signaling process underlying erbB receptor-mediated glia-neuron bidirectional communication, and discovered a novel gene that might represent a second upstream component of the hypothalamic regulatory network controlling female sexual development. We now propose studies to define the importance of these newly discovered systems in neuroendocrine glia-neuronal communication and the impact they may exert on the initiation of female puberty. To this end, the following aims are proposed: 1) To test the hypothesis that TACE, a metalloproteinase involved in the ectodomain cleavage of erbB ligands and erbB receptors, is required for excitatory amino acids to induce glial TGFa release, and thus it is important for the neuron-glia mediated control of puberty. 2) To test the hypothesis that glial expression of SynCAM, an intercellular adhesion molecule found at reduced levels in astrocytes of erbB-4-deficient mice, is involved in the glial-neuron control of female puberty. 3) To test the hypothesis that TTF-1, a homeodomain gene required for the normal timing of female puberty, is an upstream coordinator of the glial-neuronal interactions underlying the pubertal activation of LHRH secretion. 4) To examine the hypothesis that a novel gene, termed EAP-1 (Enhanced At. Puberty-1) belongs - along with TTF-1 - to the hierarchy of controlling genes involved in the transcriptional regulation of the pubertal process.