血友病B基因突变的研究

Study on mutations in hemophilia B patient factor Ⅸ gene

目的 为了研究血友病B因子Ⅸ (FⅨ )分子缺陷的发生机制。方法 应用多聚酶链反应 (PCR)、单链构型多态性 (SSCP)和双链DNA直接荧光测序等技术对 1例重度血友病B患者FⅨ基因进行研究。结果 发现该患者FⅨ基因外显子Ⅷ的 36 3bpDNA片段上 ,在第 30 790位核苷酸发生碱基替换T(GTT)→A(GTA) ,形成编码缬氨酸的同义点突变。此外 ,还发现在第 310 6 4位的胞苷 (C)缺失。该缺失突变 ,导致阅读框架改变 ,并导致在第 310 83～ 310 85位提前形成终止密码子TAG。结论 由于FⅨ基因外显子Ⅷ编码FⅨ催化结构区域 ,该基因缺失突变可严重引起催化结构区域的异常 ,导致FⅨ的分子缺陷和凝血功能障碍 ,从而导致严重的血友病B。

Objective To study the mechanism of molecular defect of factor Ⅸ(FⅨ)in hemophilia B patient.Methods Polymerase chain reaction(PCR)and Single Strand Conformation Polymorphism combined with direct sequencing were used to analyze the amplified DNA fragment containing exon 8 of factor Ⅸ gene in a hemophilia B patient.Result A point mutation was found at nucleotide 30790 resulting in T(GTT)to A(GTA)substitution.A deletion of C was found at nucleotide 31064,leading to reading frame shift and change of codon 321 of Leu in normal factor Ⅸ to stop codon(at nucleotide 31083-31085).Conclusion Exon 7 and 8,encoding the serine protease or catalytic domain,is responsible for the proteolysis of factor Ⅹ to Ⅹa.Mutation of FⅨ gene leads to molecular defect of FⅨ and causes a severe reduction of FⅨ clotting activity in hemophilia B.