CELL SPECIFIC TYROSINE HYDROXYLASE GENE TRANSCRIPTION

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Tyrosine hydroxylase (TH) is the rate-limiting enzyme in the biosynthesis of catecholamines, major neurotransmitters-hormones released by adrenal medullary cells and by life-supporting neurons. TH activity increases with enhanced catecholamine biosynthesis, in part by elevated expression of TH mRNA. The TH gene is only expressed in cells which release catecholamines suggesting a regulation by precise cell-specific molecular mechanisms. These include interactions between several segments of DNA (cis-elements) located in the upstream or 5' flanking region of the TH gene and nuclear proteins (trans-acting factors) which bind in a sequence specific fashion to these cis-elements. Our data suggest that one element is an AP-1-like sequence in the 5' DNA which interacts in a cellspecific manner with protein(s) found only in nuclear extracts from THexpressing cell lines,' i.e., PC-12 cells. The first specific aim is to isolate and characterize the protein which recognizes this AP-1-like sequence. in the second specific aim, antibodies to this protein will be Used for immunohistochemical studies in mouse embryos in combination with PCR and in situ hybridization to determine the temporal and spatial onset of expression of the gene which encodes this trans-acting factor. By comparing these data, with the first appearance of immunoreactive TH in cells, insight will be gained into the role of the AP-1-like binding protein in the embryologic commitment to the expression of the catecholaminergic phenotype. The last specific aim will employ the transgenic mouse model to investigate the role of the AP-1-like cis-element as well as additional cis-elements located upstream of the TH coding sequence in the cell-specific expression of the TH gene in the whole animal. Ultimately, these results may suggest novel approaches to treat diseases, e.g., Parkinson's Disease, a sinister malady ultimately leading to an almost complete loss of voluntary locomotor control.