Somatic mosaicism and female-to-female transmission in a kindred with hemophilia B (factor IX deficiency).

Abstract A novel T to C point mutation at −60 in the gene for coagulant Factor VII results in life-long severe coagulant Factor VII deficiency in post-pubertal twin males. The clinical course of these patients provides an informative in vivo example of the regulation of expression of vitamin K-dependent clotting protein Factor VII. An analogous point mutation in the HNF4 binding site in the Factor IX gene results in the clinical phenotype Hemophilia B Leyden, a sex-linked antigen-negative Factor IX deficiency that resolves post-puberty. The affected Factor VII deficient patients have prolonged prothrombin times (46 and 52 secs), normal aPTTs and decreased FVII levels of FVII:Coagulant activity: < 1% and FVII:Antigen: < 3%. The −60 mutation, ACTTTG → ACTCTG occurs 9 base pairs before the start site of transcription and 59 bps before the before the start site of translation. The twins are compound heterozygotes and also possess a mutation in exon 8 at amino acid 348, a mutation that has previously been reported to cause FVII deficiency. Both affected individuals have recurrent target joint hemorrhage (shoulder, elbow, ankle) requiring replacement therapy 6–12 times/year. Results: Gel mobility shift assays using a radio-labeled probe spanning from −76 to −46 in the FVII promoter region demonstrate the loss of binding of transcription factor HNF-4. Transient transfection assays in HepG2 cells using 186 bps of the mutant and the wildtype promoters (−185 to +1) revealed a loss of expression with the mutant allele. Co-transfection with an HNF4 expression plasmid resulted in an increase in expression of the wildetype construct in HeLa cells, a non-hepatic cell line. However, co-transfection of the HNF4 expression plasmid failed to increase expression with the construct containing the mutant allele sequence. Conclusion: The lack of phenotypic change of the FVII:C in 19 yo twin boys provides dynamic support of the necessity of an overlapping androgen binding site in the homologous Factor IX gene as responsible for the phenotypic resolution of Factor IX deficiency (Hemophilia B Leyden) post-puberty. It is of interest that an increase in FVII:C did not occur with advancing age in FVII deficiency due to this HNF4 binding site mutation.

Download Full-text

Factor IX Chongqing: a New Mutation in the Calcium-Binding Domain of Factor IX Resulting in Severe Hemophilia B

Thrombosis and Haemostasis ◽

10.1055/s-0038-1645679 ◽

1990 ◽

Vol 63 (01) ◽

pp. 024-026 ◽

Cited By ~ 7

Author(s):

N S Wang ◽

M Zhang ◽

A R Thompson ◽

S-H Chen

Keyword(s):

Calcium Binding ◽

Somatic Mosaicism ◽

Chinese Patient ◽

Factor Ix ◽

Hemophilia B ◽

Severe Hemophilia ◽

New Mutation ◽

Exon 2 ◽

Calcium Dependent ◽

Gla Domain

SummaryA Chinese patient with sporadic, severe hemophilia B was found to have a low level of total factor IX antigen (3.5 U/dl), but less apparent antigen in an assay using a calcium-dependent antibody fraction (1.1 U/dl). This suggested a defect in the factor IX Gla domain coded mainly by exon 2 of the factor IX gene. Exon 2 was therefore amplified and sequenced. An A to T substitution was found at nucleotide 6455 of the patient’s factor IX gene. This transversion changes the codon for Glu 27 in normal factor IX to a codon for Val. Since Glu 27 becomes an essential Gla residue, the defect should result in altered calcium-binding or calcium-dependent conformation of the patient’s factor IX. The introduction of a hydrophobic side chain also appears to affect the hemophilic protein’s stability.In leukocyte DNA from the patient’s mother, the nucleotide sequence of exon 2 was entirely normal. Thus, barring somatic mosaicism within her germ cells, the new mutation occurred in oogenesis of her ovary.

Download Full-text

Purified factor IX using monoclonal immunoaffinity technique: clinical trials in hemophilia B and comparison to prothrombin complex concentrates

Blood ◽

10.1182/blood.v79.3.568.568 ◽

1992 ◽

Vol 79 (3) ◽

pp. 568-575 ◽

Cited By ~ 55

Author(s):

HC Kim ◽

CW McMillan ◽

GC White ◽

GE Bergman ◽

MW Horton ◽

...

Keyword(s):

Monoclonal Antibody ◽

Vitamin K ◽

Half Life ◽

Viral Infections ◽

Factor Ix ◽

Hemophilia B ◽

Terminal Phase ◽

Factor Ix Deficiency ◽

In Vivo Recovery

Abstract Replacement therapy for hemophilia B (factor IX deficiency) using prothrombin complex concentrate (PCC) has been associated with serious complications of thromboembolic events and transmission of viral infections. Monoclonal antibody-purified factor IX (Mononine) provides a highly purified factor IX concentrate, while eliminating other vitamin K-dependent factors (II, VII, and X). Mononine was evaluated for in vivo recovery, half-life, and for its safety and efficacy in 10 patients with hemophilia B. The in vivo recovery of factor IX with Mononine was a 0.67 +/- 0.14 U/dL (mean +/- SD) increase per 1U/kg of infused factor IX, and the biologic half-life (t1/2), determined using the terminal phase of elimination, was 22.6 +/- 8.1 hours. Comparison of in vivo recovery of other vitamin K-dependent factors following a single infusion of either Mononine or PCC showed that, whereas Mononine infusion caused no changes in other vitamin K-dependent factors or in prothrombin activation fragment (F1+2), PCC infusion was associated with significant increases of factors II (2.7 U/dL per 1 U/dL of IX increase) and X (2.2 U/dL for 1 U/dL for 1 U/dL of IX). Patients who used Mononine as their sole therapeutic material during the 12-month period showed an excellent response in hemostasis for their bleeding episodes. Their experience with long-term use of Mononine was at least equivalent to their previous experience with PCC in the frequency and amount of factor usage. No patients developed antibody against mouse IgG or an increase in IX inhibitor during the 12-month period. These results indicate that monoclonal antibody-purified factor IX concentrate provides hemostatically effective factor IX replacement while avoiding extraneous thrombogenic substances.

Download Full-text

Somatic mosaicism and compound heterozygosity in female hemophilia B

Blood ◽

10.1182/blood.v96.4.1585 ◽

2000 ◽

Vol 96 (4) ◽

pp. 1585-1587 ◽

Cited By ~ 17

Author(s):

Jean-Marc Costa ◽

Dominique Vidaud ◽

Ingrid Laurendeau ◽

Michel Vidaud ◽

Edith Fressinaud ◽

...

Keyword(s):

Splice Site ◽

Somatic Mosaicism ◽

Splice Site Mutation ◽

Factor Ix ◽

Hemophilia B ◽

Hemorrhagic Diathesis ◽

Site Mutation ◽

History Of ◽

Sporadic Cases ◽

In Trans

Abstract Sequencing the complete factor IX gene of 2 sisters with hemophilia B with different phenotypes and no family history of hemorrhagic diathesis revealed a common 5′ splice site mutation in intron 3 (T6704C) in both and an additional missense mutation (I344T) in one. The presence of dysfunctional antigen in the latter strongly suggested that these mutations are in trans. Neither mutation was found in leukocyte DNA from the asymptomatic parents, but the mother was in somatic mosaicism for the shared splice site mutation. This case illustrates the importance of defining the phenotype and considering somatic mosaicism in sporadic cases. It underlines the limitations of complete gene sequencing for the detection of mosaicism and has implication for genetic counseling.

Download Full-text

In vivo hepatic gene therapy: complete albeit transient correction of factor IX deficiency in hemophilia B dogs.

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.91.6.2353 ◽

1994 ◽

Vol 91 (6) ◽

pp. 2353-2357 ◽

Cited By ~ 178

Author(s):

M. A. Kay ◽

C. N. Landen ◽

S. R. Rothenberg ◽

L. A. Taylor ◽

F. Leland ◽

...

Keyword(s):

Gene Therapy ◽

Factor Ix ◽

Hemophilia B ◽

Factor Ix Deficiency

Download Full-text

Somatic mosaicism and compound heterozygosity in female hemophilia B

Blood ◽

10.1182/blood.v96.4.1585.h8001585_1585_1587 ◽

2000 ◽

Vol 96 (4) ◽

pp. 1585-1587

Author(s):

Jean-Marc Costa ◽

Dominique Vidaud ◽

Ingrid Laurendeau ◽

Michel Vidaud ◽

Edith Fressinaud ◽

...

Keyword(s):

Splice Site ◽

Somatic Mosaicism ◽

Splice Site Mutation ◽

Factor Ix ◽

Hemophilia B ◽

Hemorrhagic Diathesis ◽

Site Mutation ◽

History Of ◽

Sporadic Cases ◽

In Trans

Sequencing the complete factor IX gene of 2 sisters with hemophilia B with different phenotypes and no family history of hemorrhagic diathesis revealed a common 5′ splice site mutation in intron 3 (T6704C) in both and an additional missense mutation (I344T) in one. The presence of dysfunctional antigen in the latter strongly suggested that these mutations are in trans. Neither mutation was found in leukocyte DNA from the asymptomatic parents, but the mother was in somatic mosaicism for the shared splice site mutation. This case illustrates the importance of defining the phenotype and considering somatic mosaicism in sporadic cases. It underlines the limitations of complete gene sequencing for the detection of mosaicism and has implication for genetic counseling.

Download Full-text