Identification of a third rearrangement at Xq28 that causes severe hemophilia A as a result of homologous recombination between inverted repeats.
BACKGROUND
Intrachromosomal homologous recombination between inverted repeats on the X chromosome account for about half of severe hemophilia A cases. Repeats in F8 intron 1 and intron 22 can recombine with homologous inverted repeats located about 200 kb upstream and 500 kb downstream of F8, respectively, resulting in partial sequence inversion of the F8 open reading frame and, subsequently, no functional protein production.


OBJECTIVE
In the present study, we characterize a third novel homologous recombination at Xq28 consistent with absence of F8 transcription that we previously reported for the affected chromosome of the index patient as well as his mother and sister.


RESULTS
The rearrangement occurs between a repeat in F8 intron 1 (Int1R-1) and an inverted identical repeat (Int1R-2d) in intron 2 of a duplicated copy of IKBKG located about 386 kb upstream of F8. The rearrangement was confirmed by Southern blot and inverse PCR and results in failure of PCR amplification across Int1R-1.


CONCLUSIONS
We developed a PCR-based diagnostic method that can be used to screen for this genetic rearrangement in cases of severe hemophilia A for which mutations cannot be identified.
Institute of Experimental Hematology and Transfusion Medicine, University of Bonn, Bonn, Germany.
B
B
Pezeshkpoor
S
S
Rost
J
J
Oldenburg
O
O
El-Maarri
D001483:Base Sequence; D015139:Blotting, Southern; D056905:Chromosome Breakpoints; D041321:Chromosomes, Human, X; D055028:Comparative Genomic Hybridization; D005169:Factor VIII / Q000235:genetics*; D005260:Female; D020440:Gene Duplication; D015321:Gene Rearrangement; D020022:Genetic Predisposition to Disease; D005820:Genetic Testing / Q000379:methods; D005858:Germany; D006467:Hemophilia A / Q000097:blood / Q000175:diagnosis / Q000235:genetics*; D059765:Homologous Recombination; D006801:Humans; D051550:I-kappa B Kinase / Q000235:genetics; D007438:Introns; D055029:Inverted Repeat Sequences; D008297:Male; D008969:Molecular Sequence Data; D060885:Multiplex Polymerase Chain Reaction; D010375:Pedigree; D010641:Phenotype; D012720:Severity of Illness Index
C491731:IKBKG protein, human; C078147:F8 protein, human; D005169:Factor VIII; D051550:I-kappa B Kinase