title: Tandem inversion duplication within F8 Intron 1 associated with mild haemophilia A.
abstract: In approximately 90% of mild haemophilia A (HA) patients, a missense mutation can be identified using complete gene sequencing. In this study, multiplex ligation-dependent probe amplification analysis was performed as a second step in 10 French-speaking Belgian with mild HA presenting no detectable causal mutation by complete sequencing of the factor VIII (FVIII) (F8) gene's 26 exons and its 1.2 kb of contiguous promoter sequence. This gene dosage technique enabled the detection of exon 1 duplications of F8 in three apparently unrelated subjects. Using array-comparative genomic hybridization, breakpoint analysis delimited the duplication extent to 210 kb in the F8 intron 1 and VBP1 gene intragenic position. We postulated that the rearrangement responsible for this duplication, never before reported, could be attributed to a symmetrical tandem inversion duplication, resulting in a large 233 kb rearrangement of F8 intron 1. This rearranged intron should lead to the production of a small number of normal mRNA transcripts in relation to the mild HA phenotype. Our analysis of the entire F8 mRNA from index case 1, particularly the segment containing exons 1-9, revealed normal amplification and sequencing. Reduced plasma FVIII antigen levels caused by cross-reacting material is associated with a quantitative deficiency of plasma FVIII. Male patients were unresponsive to desmopressin (1-deamino-8-D-arginine vasopressin). All patients displayed identical F8 haplotypes, despite not being related, which suggests a possible founder effect caused by a 210 kb duplication involving F8 exon 1.
authors.affiliation: Center of Human Genetics UCLouvain, Cliniques Universitaires Saint-Luc, Bruxelles, Belgium.|Institut de Recherche Expérimentale et Clinique (IREC), Université Catholique de Louvain, Bruxelles, Belgium.
authors.forename: N
authors.initials: N
authors.lastname: Lannoy
authors.affiliation: Center of Human Genetics UCLouvain, Cliniques Universitaires Saint-Luc, Bruxelles, Belgium.
authors.forename: C
authors.initials: C
authors.lastname: Bandelier
authors.affiliation: Center of Human Genetics, Institut de Pathologie et de Génétique (IPG), Charleroi (Gosselies), Belgium.
authors.forename: B
authors.initials: B
authors.lastname: Grisart
authors.affiliation: Department of Hemato-oncology, Centre Hospitalier Regional de Huy, Huy, Belgium.
authors.forename: M
authors.initials: M
authors.lastname: Reginster
authors.affiliation: Hemostasis Laboratory, Department of Biological Chemistry, Centre Hospitalier Regional de Liège, Liege, Belgium.
authors.forename: E
authors.initials: E
authors.lastname: Ronge-Collard
authors.affiliation: Laboratory of Human Molecular Genetics de Duve Institute, Université Catholique de Louvain, Bruxelles, Belgium.
authors.forename: M
authors.initials: M
authors.lastname: Vikkula
authors.affiliation: Institut de Recherche Expérimentale et Clinique (IREC), Université Catholique de Louvain, Bruxelles, Belgium.|Haemostasis and Thrombosis Unit, Haemophilia Clinic, Division of Haematology, Cliniques Universitaires Saint-Luc, Bruxelles, Belgium.
authors.forename: C
authors.initials: C
authors.lastname: Hermans
mesh_terms: D000293:Adolescent; D007446:Chromosome Inversion; D041321:Chromosomes, Human, X; D055028:Comparative Genomic Hybridization; D056915:DNA Copy Number Variations; D004252:DNA Mutational Analysis; D005091:Exons; D005169:Factor VIII / Q000235:genetics*; D005260:Female; D020440:Gene Duplication; D006239:Haplotypes; D006467:Hemophilia A / Q000235:genetics* / Q000473:pathology; D006801:Humans; D007438:Introns; D008297:Male; D008875:Middle Aged; D010375:Pedigree; D010641:Phenotype; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism; D012720:Severity of Illness Index
chemical_list: D012333:RNA, Messenger; D005169:Factor VIII
keywords: CGH array; F8 gene; MLPA; duplication; haemophilia A