GENETIC REGULATION OF THE HEPATIC ACUTE PHASE RESPONSE

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Homeostasis of mammals is strongly dependent on correct developmental stage-, tissue- and hormone-specific expression of plasma proteins. Regulated plasma protein production is especially important during systemic injury when the body's demand for essential plasma proteins must be met by an immediate increase in hepatic synthesis. The overall goal of this project is to characterize the largely unknown genetic elements governing the activity of plasma protein genes, in particular those induced by systemic injury. In order to identify such elements, inbred strains and wild derived species of mice had been surveyed for genetic variants in plasma protein gene expression. M. caroli revealed two exceptional features: 1) the structural gene for alpha 1-acid glycoprotein (AGP) has been amplifed to 4-6 copies, each encoding distinct forms with different degrees of inducibility by inflammation, and 2) the regulation of the single, liver specific gene for alpha1-antitrypsin (AT) has been altered such that the gene is equally expressed in liver and in kidney. These unique genetic properties, evolved in M. caroli, will be used to assess those gene elements determining a) the acute phase induction of AGP gene and b) the tissue-specificity of the AT gene expression. The experimental approaches will be as follows: 1) The structural genes for high and low inducible AGPs and for AT will be isolated. 2) The transcriptional activity and regulatory response of the different AGP genes will be tested by introducing the genes into human and rat hepatoma cells which are responsive to the two most potent mediators of hepatic acute phase response, the hepatocyte stimulating factor and glucocorticoids. To identify the liver and kidney specificity of AT gene expression, the activity of the M. caroli AT gene will be measured and compared to the M. domesticus AT gene by transfection into hepatic and renal tissue culture cells. After demonstrating correct regulation of the AGP and AT genes, the cis-acting regulatory elements will be localized relative to the structural genes. 3) The extent to which functional AGP and AT gene sequences support correct tissue, hormone and developmental regulation will be assessed in transgenic mice. 4) Lastly, the cellular factors interacting specifically with the cis-acting regulatory elements will be identified. The results from these studies on M. caroli genes will provide new insights into the signals controlling tissue specific and inflammation-inducibility of plasma protein genes.