title: Skipping of exon 27 in C3 gene compromises TED domain and results in complete human C3 deficiency.
abstract: Primary deficiency of complement C3 is rare and usually associated with increased susceptibility to bacterial infections. In this work, we investigated the molecular basis of complete C3 deficiency in a Brazilian 9-year old female patient with a family history of consanguinity. Hemolytic assays revealed complete lack of complement-mediated hemolytic activity in the patient's serum. While levels of the complement regulatory proteins Factor I, Factor H and Factor B were normal in the patient's and family members' sera, complement C3 levels were undetectable in the patient's serum and were reduced by at least 50% in the sera of the patient's parents and brother. Additionally, no C3 could be observed in the patient's plasma and cell culture supernatants by Western blot. We also observed that patient's skin fibroblasts stimulated with Escherichia coli LPS were unable to secrete C3, which might be accumulated within the cells before being intracellularly degraded. Sequencing analysis of the patient's C3 cDNA revealed a genetic mutation responsible for the complete skipping of exon 27, resulting in the loss of 99 nucleotides (3450-3549) located in the TED domain. Sequencing of the intronic region between the exons 26 and 27 of the C3 gene (nucleotides 6690313-6690961) showed a nucleotide exchange (T→C) at position 6690626 located in a splicing donor site, resulting in the complete skipping of exon 27 in the C3 mRNA.
authors: Department of Immunology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
authors: Karina Ribeiro
authors: KR
authors: da Silva
authors: Department of Immunology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
authors: Tatiana Rodrigues
authors: TR
authors: Fraga
authors: Department of Immunology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
authors: Juliana Faggion
authors: JF
authors: Lucatelli
authors: Faculty of Medicine, ABC, Santo André, Brazil.
authors: Anete Sevciovic
authors: AS
authors: Grumach
authors: Department of Immunology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil. Electronic address: louisaac@icb.usp.br.
authors: Lourdes
authors: L
authors: Isaac
mesh_terms: D000328:Adult; D017398:Alternative Splicing; D001938:Brazil; D002648:Child; D003176:Complement C3 / Q000737:chemistry / Q000172:deficiency* / Q000235:genetics* / Q000276:immunology; D003170:Complement Pathway, Alternative / Q000276:immunology; D003171:Complement Pathway, Classical / Q000276:immunology; D004252:DNA Mutational Analysis; D005091:Exons; D005260:Female; D005838:Genotype; D006801:Humans; D007153:Immunologic Deficiency Syndromes / Q000175:diagnosis / Q000235:genetics* / Q000276:immunology; D008297:Male; D009154:Mutation; D010375:Pedigree; D054730:Protein Interaction Domains and Motifs / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics
chemical_list: D003176:Complement C3; D012333:RNA, Messenger
keywords: C3 deficiency; Complement system; Exon skipping