TISSUE EXPRESSION STUDIES ON THE MOUSE ACYL-COA-CHOLESTEROL ACYLTRANSFERASE GENE (ACACT) - FINDINGS SUPPORTING THE EXISTENCE OF MULTIPLE CHOLESTEROL ESTERIFICATION ENZYMES IN MICE

Cholesterol esterification is involved in the regulation of cellular c holesterol content and has been hypothesized to play a role in importa nt physiologic processes including intestinal cholesterol absorption, hepatic lipoprotein production, and macrophage foam cell formation in atherosclerotic lesions. Although intitial studies of the mouse acyl C oA:cholesterol acyltransferase gene (Acact) suggested that its gene pr oduct was responsible for cholesterol esterification in most tissues, we observed recently that Acact(-/-) mice have only tissue-specific re ductions in cholesterol esterification. To better understand the role of Acact in cholesterol esterification, we used in situ hybridization and immunoblotting to perform tissue expression studies in wild-type m ice. We found high levels of Acact expression in steroidogenic tissues , sebaceous glands, and atherosclerotic lesions, but not in the liver or the small intestine. These data support the hypothesis that multipl e cholesterol esterification enzymes exist in mammals and that another enzyme is likely to be responsible for cholesterol esterification act ivity in mouse liver and intestine.