Hereditary angioneurotic edema (HANE) is a dominantly inherited disease characterized by recurrent episodes of edema of the skin and mucous membranes. Involvement of the larynx may result in death due to asphyxiation. The disease occurs in individuals who are heterozygous for deficiency of C1 inhibitor, a plasma protease inhibitor that regulates activation of the complement and kinin-forming systems. Deficiency may result from lack of expression C1 inhibitor (type I) or from expression of a dysfunctional mutant C1 inhibitor molecule (type II). The overall goals of the proposed project are to define the molecular genetic defects in the C1 inhibitor gene that result in HANE, to delineate those structured features of C1 inhibitor that are important for its function, and to analyze the regulation of transcription of the C1 inhibitor gene. The C1 inhibitor gene (or relevant portions thereof) from patients with both type I and type II HANE will be cloned and sequenced. About 15-20% of type I result from deletions, all of which appear to be different from one another. Several of these will be characterized in order to define whether they result from the same or different mechanisms. Similarly, several individuals from the larger group of type I patients without a deletion will be analyzed to define the distribution of the types of mutations that produce deficiency. The analysis of defects resulting in dysfunctional C1 inhibitor (type II) will concentrate on those with mutations outside the active center arginine. These dysfunctional proteins, and C1 INH modified at the same sites in the molecule by site directed mutagenesis, will be expressed in vitro, and their function analyzed. Other specific residues thought to be of functional importance will be analyzed in the same way. C1 inhibitor expressed in a prokaryotic system and eukaryotic expression of C1 inhibitor truncated at its amino terminal end (which contains most of the carbohydrate) will be used to define the role of carbohydrate in its function. As another probe of function, and autoantibody to C1 inhibitor from a patient with acquired angioedema will be used to help define regions of the molecule required for function. The regulation of synthesis of C1 inhibitor by cytokines and androgens also will be examined and will lead to study of promoters and enhancer elements in the C1 INH gene. Definition of synthesis regulation could lead to other therapeutic approaches aimed toward enhancement of synthesis, but without the complications associated with current therapy.
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