title: Deletion of the factor IX gene as a result of translocation t(X;1) in a girl affected by haemophilia B.
abstract: A balanced de novo translocation t(X;1) is described in a girl with severe haemophilia B. The translocated X was shown cytologically to be preferentially active, and methylation analysis of the DXS255 locus confirmed the skewed X-inactivation with the paternal allele being the active one. Cytogenetic and molecular analysis showed that this chromosomal rearrangement led to the deletion of at least part of the factor IX gene. Therefore, the girl was heterozygous for factor IX deficiency and expression of her clinical phenotype was the result of the inactivation of the normal maternal X chromosome. The localization of one of the X chromosome translocation breakpoints in YAC clone 957F9, that was demonstrated to map distally to the factor IX gene, revealed the complexity of this chromosomal rearrangement.
authors.affiliation: Departamento de Biologia, Universidade de São Paulo, Instituto da Criança, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: A C
authors.initials: AC
authors.lastname: Krepischi-Santos
authors.forename: J D
authors.initials: JD
authors.lastname: Carneiro
authors.forename: M
authors.initials: M
authors.lastname: Svartman
authors.forename: I
authors.initials: I
authors.lastname: Bendit
authors.forename: V
authors.initials: V
authors.lastname: Odone-Filho
authors.forename: A M
authors.initials: AM
authors.lastname: Vianna-Morgante
mesh_terms: D015139:Blotting, Southern; D002648:Child; D002871:Chromosome Banding; D002878:Chromosomes, Human, Pair 1; D004303:Dosage Compensation, Genetic; D005164:Factor IX / Q000235:genetics*; D005260:Female; D017353:Gene Deletion; D002836:Hemophilia B / Q000235:genetics*; D006579:Heterozygote; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D014178:Translocation, Genetic; D014960:X Chromosome
chemical_list: D005164:Factor IX