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Identification and Genetic Analysis of a Factor IX Gene Intron 3 Mutation in a Hemophilia B Pedigree in China.

ABSTRACT: Hemophilia B is caused by coagulation defects in the factor IX gene located in Xq27.1 on the X chromosome. A wide range of mutations, showing extensive molecular heterogeneity, have been described in hemophilia B patients. Our study was aimed at genetic analysis and prenatal diagnosis of hemophilia B in order to further elucidate the pathogenesis of the hemophilia B pedigree in China.Polymerase chain reaction amplification and direct sequencing of all the coding regions was conducted in hemophilia B patients and carriers. Prenatal diagnosis of the proband was conducted at 20 weeks.We identified the novel point mutation 10.389 A>G, located upstream of the intron 3 acceptor site in hemophilia B patients. The fetus of the proband's cousin was identified as a carrier.Our identification of a novel mutation in the F9 gene associated with hemophilia B provides novel insight into the pathogenesis of this genetically inherited disorder and also represents the basis of prenatal diagnosis.

SUBMITTER: Cao DH

PROVIDER: S-EPMC4287022 | biostudies-literature | 2014 Sep

REPOSITORIES: biostudies-literature

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Identification and Genetic Analysis of a Factor IX Gene Intron 3 Mutation in a Hemophilia B Pedigree in China.

Cao Dong-Hua DH Liu Xiao-Li XL Mu Kai K Ma Xiang-Wei XW Sun Jing-Li JL Bai Xiao-Zhong XZ Lin Chang-Kun CK Jin Chun-Lian CL

Turkish journal of haematology : official journal of Turkish Society of Haematology 20140901 3

<h4>Objective</h4>Hemophilia B is caused by coagulation defects in the factor IX gene located in Xq27.1 on the X chromosome. A wide range of mutations, showing extensive molecular heterogeneity, have been described in hemophilia B patients. Our study was aimed at genetic analysis and prenatal diagnosis of hemophilia B in order to further elucidate the pathogenesis of the hemophilia B pedigree in China.<h4>Materials and methods</h4>Polymerase chain reaction amplification and direct sequencing of ...[more]

PMID: 25330515

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Project description:BACKGROUND:The prevention of bleeding with adequately sustained levels of clotting factor, after a single therapeutic intervention and without the need for further medical intervention, represents an important goal in the treatment of hemophilia. METHODS:We infused a single-stranded adeno-associated viral (AAV) vector consisting of a bioengineered capsid, liver-specific promoter and factor IX Padua (factor IX-R338L) transgene at a dose of 5×1011 vector genomes per kilogram of body weight in 10 men with hemophilia B who had factor IX coagulant activity of 2% or less of the normal value. Laboratory values, bleeding frequency, and consumption of factor IX concentrate were prospectively evaluated after vector infusion and were compared with baseline values. RESULTS:No serious adverse events occurred during or after vector infusion. Vector-derived factor IX coagulant activity was sustained in all the participants, with a mean (±SD) steady-state factor IX coagulant activity of 33.7±18.5% (range, 14 to 81). On cumulative follow-up of 492 weeks among all the participants (range of follow-up in individual participants, 28 to 78 weeks), the annualized bleeding rate was significantly reduced (mean rate, 11.1 events per year [range, 0 to 48] before vector administration vs. 0.4 events per year [range, 0 to 4] after administration; P=0.02), as was factor use (mean dose, 2908 IU per kilogram [range, 0 to 8090] before vector administration vs. 49.3 IU per kilogram [range, 0 to 376] after administration; P=0.004). A total of 8 of 10 participants did not use factor, and 9 of 10 did not have bleeds after vector administration. An asymptomatic increase in liver-enzyme levels developed in 2 participants and resolved with short-term prednisone treatment. One participant, who had substantial, advanced arthropathy at baseline, administered factor for bleeding but overall used 91% less factor than before vector infusion. CONCLUSIONS:We found sustained therapeutic expression of factor IX coagulant activity after gene transfer in 10 participants with hemophilia who received the same vector dose. Transgene-derived factor IX coagulant activity enabled the termination of baseline prophylaxis and the near elimination of bleeding and factor use. (Funded by Spark Therapeutics and Pfizer; ClinicalTrials.gov number, NCT02484092 .).

Project description:BackgroundIn patients with severe hemophilia B, gene therapy that is mediated by a novel self-complementary adeno-associated virus serotype 8 (AAV8) vector has been shown to raise factor IX levels for periods of up to 16 months. We wanted to determine the durability of transgene expression, the vector dose-response relationship, and the level of persistent or late toxicity.MethodsWe evaluated the stability of transgene expression and long-term safety in 10 patients with severe hemophilia B: 6 patients who had been enrolled in an initial phase 1 dose-escalation trial, with 2 patients each receiving a low, intermediate, or high dose, and 4 additional patients who received the high dose (2×10(12) vector genomes per kilogram of body weight). The patients subsequently underwent extensive clinical and laboratory monitoring.ResultsA single intravenous infusion of vector in all 10 patients with severe hemophilia B resulted in a dose-dependent increase in circulating factor IX to a level that was 1 to 6% of the normal value over a median period of 3.2 years, with observation ongoing. In the high-dose group, a consistent increase in the factor IX level to a mean (±SD) of 5.1±1.7% was observed in all 6 patients, which resulted in a reduction of more than 90% in both bleeding episodes and the use of prophylactic factor IX concentrate. A transient increase in the mean alanine aminotransferase level to 86 IU per liter (range, 36 to 202) occurred between week 7 and week 10 in 4 of the 6 patients in the high-dose group but resolved over a median of 5 days (range, 2 to 35) after prednisolone treatment.ConclusionsIn 10 patients with severe hemophilia B, the infusion of a single dose of AAV8 vector resulted in long-term therapeutic factor IX expression associated with clinical improvement. With a follow-up period of up to 3 years, no late toxic effects from the therapy were reported. (Funded by the National Heart, Lung, and Blood Institute and others; ClinicalTrials.gov number, NCT00979238.).

Dataset Information

Identification and Genetic Analysis of a Factor IX Gene Intron 3 Mutation in a Hemophilia B Pedigree in China.

Publications

Identification and Genetic Analysis of a Factor IX Gene Intron 3 Mutation in a Hemophilia B Pedigree in China.

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