FIX基因全外显子测序技术在血友病B基因携带者检测及产前基因诊断中的应用

FIX gene all exons sequencing technology in hemophilia B gene carriers detection and the application of prenatal gene diagnosis

目的探索应用FIX基因全外显子测序技术进行血友病B（HB）基因携带者检测和产前基因诊断。方法在取得5个无血缘关系的汉族HB家系成员知情同意后，采集相关家系成员标本。3个产前诊断标本中，2例为胎儿脐血标本，1例为羊水标本。从标本中提取基因组DNA，通过PCR扩增FⅨ基因所有外显子及其侧翼序列，将产物进行全外显子直接测序。结果5个家系的HB患者以及FIX基因携带者共检出5种突变：C．484C〉T（P．R162X）、C．1022G〉A（P．R341Q）、c．1135C〉T（P．R379X）、c．799C〉T（P．H267Y）和c．1232G〉T（P．$411I）。在产前诊断中，发现1例c．484C〉T（P．R162X）突变，另2例未检出FIX基因突变的胎儿出生后血浆FIX促凝活性分别为52．7％和76．2％。结论首次报道中国汉族HB家系FⅨ基因c．1022G〉A（P．R341Q）、C．1135C〉T（P．R379X）、c．799C〉T（P．H267Y）和C．1232G〉T（P．$41¨）突变；在严格的质量控制下，FⅨ基因全外显子直接测序是一种快速准确的诊断HB基因携带者及产前基因诊断的方法。

Objective To establish a feasible protocol to provide genetic diagnosis and prenatal diag- nosis in Chinese hemophilia patients and their relatives by direct exon sequencing. Methods In our study, genetic diagnosis was performed on 5 unrelated families with informed consent, which included 3 pregnant women who asked for prenatal diagnosis. Umbilical cord blood was obtained from 2 fetuses and amniotic fluid from another fetus. After extraction of the genomic DNA, all of the exons, exon-intron boundaries and their flanks of FIX gene were amplified by polymerase chain reaction （PCR）. PCR products were detected through direct-sequencing. Results Sequence analysis indicated that the patients and carriers from 5 families have the pathogenic mutations, c. 1022 G 〉 A （ p. R341 Q）, c. 484 C 〉 T （ p. R162X）, c. 1135 C 〉 T （ p. R379X）, c. 799C 〉T （p. H267Y）, c. 1232G 〉T （p. S411I）, respectively. Except c.484 C 〉T （p. R162X）, 4 of the 5 mutations were reported firstly in Chinese population. During prenatal diagnosis, one of the fetuses was found to be affected with c. 484C 〉 T; p. R162X. The remaining two fetuses were diagnosed as normal, the results of which were later verified by post-birth diagnosis, and factor FIX activities in plasma was 52.7% and 76.2%, respectively. Conclusion In the quest of strict quality control, exon sequence on FIX gene was a rapid and accurate method for genetic diagnosis and prenatal diagnosis of hemophilia B.