C1 inhibitor gene expression in patients with hereditary angioedema: Quantitative evaluation by means of real-time RT-PCR

• Published in: Journal of Allergy and Clinical Immunology Vol. 114; no. 3; pp. 638 - 644
• Main Authors: Pappalardo, Emanuela, Zingale, Lorenza C., Cicardi, Marco
• Format: Journal Article
• Language: English
• Published: New York, NY Mosby, Inc 01.09.2004; Elsevier; Elsevier Limited
• Subjects: Allergic diseases; Angioedema; Angioedema - genetics; Angioedema - metabolism; Biological and medical sciences; C1 inhibitor; Complement C1 Inactivator Proteins - genetics; Complement C1 Inactivator Proteins - metabolism; Complement C1 Inhibitor Protein; Deoxyribonucleic acid; DNA; Down-Regulation; Female; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Gene expression; Hereditary angioedema; Humans; Immunopathology; Leukocytes, Mononuclear - metabolism; Male; Medical sciences; mRNA; Mutation; Proteins; real-time PCR; Reverse Transcriptase Polymerase Chain Reaction - methods; RNA, Messenger - genetics; RNA, Messenger - metabolism; Skin allergic diseases. Stinging insect allergies; Taq Polymerase; Italy; Hereditary angioedema; CV; C1 inhibitor; C1-INH; mRNA; real-time PCR; GAPDH; HAE; gene expression; Human; Allergy; Immunopathology; Skin disease; RNA-directed DNA polymerase; Enzyme; Transferases; Gene expression; Hereditary; Real time; Polymerase chain reaction; Nucleotidyltransferases; Angioneurotic edema; Immunology; Messenger RNA; Inhibitor; Molecular biology; Reverse transcription polymerase chain reaction; Quantitative analysis
• ISSN: 0091-6749; 1097-6825; 1365-2567
• DOI: 10.1016/j.jaci.2004.06.021

Hereditary angioedema (HAE) is caused by heterozygous defects in the C1 inhibitor (C1-INH) gene (SERPING1/C1NH). In patients' plasma C1-INH levels range between 5% and 30% of normal levels (ie, far from the 50% expected for an autosomal dominant defect). Most patients have antigenic and functional deficiency (type I HAE), and 15% have reduced C1-INH function but normal to increased antigen because of the presence of a dysfunctional protein (type II HAE). We sought to contribute to the understanding of the pattern of C1-INH gene expression in patients with HAE. We used real-time quantitative RT-PCR to measure C1-INH mRNA levels in PBMCs of 57 patients with HAE typed for mutations in the SERPING1/C1NH gene. Thirty-six different mutations were identified in genomic DNA. Compared with healthy control subjects, C1-INH mRNA was significantly and similarly reduced in patients with type I and type II HAE (40% and 47%, respectively; P < .0001). By means of direct sequencing of cDNAs, we found that 74% of patients with type I HAE carrying small mutations presented significant amounts of mutated transcripts at the mRNA level, suggesting that both allelic mRNA products were reduced to approximately 50%. In 4 patients carrying large deletions expected to fully inactivate expression from the mutant allele, C1-INH mRNA was 23% on average compared with that seen in control subjects, confirming that normal mRNA was strongly underexpressed. These new findings, combined with previous evidence of increased C1-INH consumption, might explain the plasma levels of normal C1-INH that are markedly less than the expected 50%.