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目的对1例儿童型低磷酸酶血症(HPP)患者及家系进行临床分析和基因突变检测,以探讨HPP的致病机制。方法针对1例罕见的HPP患者的典型临床特点,进行实验室检验及影像学检查。进而收集患者及其亲属外周血,提取基因组DNA。针对ALPL基因12个外显子及附近内含子区合成引物,经PCR扩增后,直接对产物测序检测突变。结果患者血碱性磷酸酶水平显著降低,骨骼具有佝偻病样改变;患者ALPL基因存在c.18delA及c.G407C两种突变。前者所致移码突变使得翻译提前终止,形成的截短蛋白(p.V7Yfs18X)丧失了发挥酶活性及骨骼矿化作用的重要区域;而c.G407C导致其编码的氨基酸由精氨酸变为脯氨酸(R136P)。进一步检索PubMed及ALPL基因突变数据库,以上突变在国内外均未见报道。临床表现正常的患者母亲及祖母、父亲分别携带c.18delA和c.G407C突变,该家系符合常染色体隐性遗传。结论 ALPL基因c.18delA和c.G407C两种新突变与HPP临床表现密切相关。
Objective To analyze the clinical analysis and gene mutation of 1 pediatric hypophosphatasia (HPP) patients and their pedigrees to explore the pathogenesis of HPP. Methods A typical case of HPP in a typical clinical features, laboratory tests and imaging studies. Then collect peripheral blood of patients and their relatives and extract genomic DNA. A total of 12 exons of ALPL gene and its adjacent intron regions were synthesized. After amplification by PCR, the products were directly sequenced to detect the mutations. Results The level of ALP in patients was significantly lower than that in controls. The skeletal samples showed rickets-like changes. There were two mutations of c.18delA and c.G407C in ALPL gene. The former caused a frameshift mutation that led to the early termination of translation. The formed truncated protein (p.V7Yfs18X) lost its important area of enzyme activity and bone mineralization; whereas c.G407C caused its encoded amino acid to change from arginine to Proline (R136P). Further search PubMed and ALPL gene mutation database, the above mutations have not been reported at home and abroad. Patients with normal clinical manifestations, mother and grandmother, father carrying c.18delA and c.G407C mutations, the family line with autosomal recessive inheritance. Conclusion The two new mutations of ALPL gene c.18delA and c.G407C are closely related to the clinical manifestations of HPP.