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Mutations in the C1 inhibitor gene that result in hereditary angioneurotic edema
A E Davis1, J J Bissler, M Cicardi
1Division of Nephrology, Children's Hospital Research Foundation, Cincinnati, Ohio 45229.
Insights
Mutations in the C1 inhibitor gene cause hereditary angioedema. Researchers found that Alu elements drive many mutations, particularly in the reactive center, impacting C1 inhibitor function.
Area of Science:
- Genetics
- Molecular Biology
- Immunology
Background:
- Hereditary angioedema is an autosomal dominant disease caused by mutations in the C1 inhibitor (C1 INH) gene.
- While plasma antigenic C1 INH levels can vary, functional levels are consistently reduced in affected individuals.
Purpose of the Study:
- To investigate mutations in the C1 INH gene and understand their impact on DNA and protein structure-function.
- To identify key regions and mechanisms underlying C1 INH dysfunction.
Main Methods:
- Analysis of mutations within the C1 INH gene.
- Investigation of DNA sequence features, including repetitive elements and polymerase pause sites.
- Characterization of dysfunctional C1 INH proteins resulting from specific mutations.
Main Results:
- A significant group of mutations involves recombinations with Alu repetitive DNA elements.
- The reactive center region shows a high mutation rate, potentially due to DNA polymerase pause sites.
- Analysis of hinge region mutants provides insights into reactive center loop interactions.
Conclusions:
- Alu elements are a major driver of C1 INH gene mutations.
- The reactive center is a mutation hotspot, influencing inhibitor function.
- Studying dysfunctional mutants reveals critical regions for C1 INH inhibitor activity.
Abstract:
Mutations in one C1 INH allele result in the autosomal dominant disease, hereditary angioedema. The plasma antigenic level of C1 INH in this disease may be low, normal, or high, while the functional level is uniformly depressed. Investigation of the mutations in the C1 INH gene reveal several key features about the DNA itself as well as protein structure-function relationships. The largest single group of mutations with a defined mechanism are recombinations associated with Alu repetitive DNA elements. Current data suggest that there may be an increased number of mutations within the region encoding the reactive center which, like some other serpins, contains both primary and secondary structure DNA polymerase pause sites. These sites may enhance the rates of mutation and evolution in the reactive center region. Some of the dysfunctional C1 INH proteins that result from hinge region mutations support models for reactive center loop interaction with beta sheet A during complex formation. The analysis of the dysfunctional mutants, therefore, suggest regions of the molecule that are important for inhibitor function.