Functional characterization of the p.A8V, p.Q370H and p.R384Q variants present in the angiopoietin 1-ANGPT1 gene

Abstract

Hereditary angioedema (HAE) is characterized by sudden episodes of swelling that cause pain, discomfort, and according to its location can cause disfigurement of the individual. Edema affects mainly the upper and lower extremities (hands and feet), gastrointestinal tract, genitalia and face. If not treated it can lead to death due to laryngeal edema. HAE is an autosomal dominant disorder resulting from mutations in C1 esterase inhibitor (SERPING1) or as a result of specific mutations in the Factor XII gene, leading to an overproduction of bradykinin. Deleterious mutations in SERPING1 are responsible for HAE types 1 and 2, and several changes in this gene have been proven to be responsible for the phenotype displayed by the patients affected by this disease.However, many patients with HAE do not possess any mutation in these two genes, and the disease is classified as HAE with unknown causes (U-HAE). Recently, Bafunno et al (2017) identified a new mutation (p.A119S) in the angiopoietin 1 gene (ANGPT1) in an Italian family with symptoms of HAE. Simultaneously, our group investigated this gene in families with HAE without mutations in the genes SERPING1 and F12 and found three variants that were described as "disease-causing" by in silico analyzes. Therefore, this work aims to study the in vitro functional activity of wild type and mutated angiopoietin (p.A8V, p.Q370H and p.R384Q), to establish the genotype-phenotype correlation of these variants. ANGPT1 containing the target mutations will be cloned and expressed in eukaryotic cells. The structure of mutated proteins will be evaluated by multimerization tests and functional analysis of permeability. The results of this project should generate important information about the role of these mutations in the clinic of patients with U-HAE and guide the genetic counseling and treatment of the disease.