A possible mechanism for Inv22-related F8 large deletions in severe hemophilia A patients with high responding factor VIII inhibitors
Article first published online: 1 OCT 2012
© 2012 International Society on Thrombosis and Haemostasis
Journal of Thrombosis and Haemostasis
Volume 10, Issue 10, pages 2099–2107, October 2012
How to Cite
FUJITA, J., MIYAWAKI, Y., SUZUKI, A., MAKI, A., OKUYAMA, E., MURATA, M., TAKAGI, A., MURATE, T., SUZUKI, N., MATSUSHITA, T., SAITO, H. and KOJIMA, T. (2012), A possible mechanism for Inv22-related F8 large deletions in severe hemophilia A patients with high responding factor VIII inhibitors. Journal of Thrombosis and Haemostasis, 10: 2099–2107. doi: 10.1111/j.1538-7836.2012.04897.x
- Issue published online: 1 OCT 2012
- Article first published online: 1 OCT 2012
- Accepted manuscript online: 20 AUG 2012 10:29AM EST
- Received 22 March 2012, accepted 31 July 2012
- gene rearrangement;
- intron 22 inversion;
- inverse shifting-PCR;
- X chromosome
Summary. Background: Intron 22 inversion (Inv22) of the coagulation factor (F)VIII gene (F8) is a frequent cause of severe hemophilia A. In addition to Inv22, a variety of F8 mutations (1492 unique mutations) causing hemophilia A have been reported, of which 171 involve deletions of over 50 bp (HAMSTeRs database; http://hadb.org.uk/). However, only 10% of these large deletions have been fully characterized at the nucleotide level.
Patients and methods: We investigated gene abnormalities in three unrelated severe hemophilia A patients with high titer FVIII inhibitors. They had previously been shown to carry large deletions of the F8, but the precise gene abnormalities remain to be elucidated.
Results: Inverse shifting-PCR (IS-PCR) Inv22 diagnostic tests revealed that these patients carried either type I or II Inv22. However, they showed a wild-type (WT) pattern in the IS-PCR Inv22 complementary tests. We further analyzed their X chromosomes to account for the puzzling results, and found that they had different centromeric breakpoints in the Inv22 X chromosomes, adjacent to the palindromic regions containing int22h-2 or -3, and their spacer region, respectively. The connections appeared to be shifted towards the telomere of the WT F8 Xq28, resulting in a new telomere with an additional intact int22h copy.
Conclusions: These gene rearrangements might result from double-strand breaks in the most distal regions of the long arms of the Inv22 X chromosomes, followed by DNA restorations using the WT F8 Xq28 by non-homologous end joining or break-induced replication; thus leading to large F8 deletions in severe hemophilia A patients.