21-羟化酶缺乏症家系的基因突变研究

Mutaation analysis in families with 21-hydroxylase deficiency

目的通过对3个21-羟化酶缺乏症家系的21-羟化酶基因（steroid21-hydroxylase gene,CYP21）直接测序研究,探讨家系中该基因突变类型。方法收集4例患者及其部分家系成员外周血,提取基因组DNA,PCR扩增CYP21基因后直接测序。结果CYP21基因序列分析共检测到6种突变类型。家系1中患者CYP21基因存在4种杂合突变：clusteE6、Q318X、A391T、P459H,其中前3种突变串联排列于同一条染色体上,P459H突变目前国内外尚未见报道,A391T为罕见突变;家系2中患者CYP21基因存在clusteE6、R483W两种杂合突变,其中R483W为罕见突变类型;家系3中患者第4外显子存在I172N纯合突变。结论在3个21-羟化酶缺乏症家系中共检测出6种突变类型,其中P459H为新发现的突变,A391T、R483W为罕见突变。虽然导致21-羟化酶缺乏症的突变主要是一些从假基因（CYP21P）转位到CYP21的序列,但随机突变也是21-羟化酶缺乏症的原因。

Objective To investigate the steroid 21-hydroxylase gene （CYP21） mutations in families with 21-hy- droxylase deficiency （21-OHD）. Methods The CYP21 gene mutations were detected in four patients with 21-hydroxylase deficiency and their relatives. The genomic DNA of the patients was isolated from whole blood. Two pairs of primers were used to amplify the CYP21 gene. The amplified PCR products were purified by agarnse gel and then directly se- quenced. Results Six kinds of mutations were found. In the first family, the patient was a compound heterozygote cartying four different mutations （cluster E6, Q318X, A391T, P459H） on CYP21 gene, three mutations （cluster E6, Q318X, A391T） were on her maternal allele, a novel mutation was found：P459H. It located at codon 459 in exon 10 and changing a prohne（CCC） to a histidine （CAC）, and A391T was a rare mutation. In the second family, two kinds of mutations were found： cluster E6 and R483W. R483W was also a rare mutation. In the third family, the sequencing of the CYP21 gene of two patients revealed a homozygous T 〉 A transition in codon 172 leading to substitution of isoleucine by asparagine （I172N）. Conclusion Six kinds of mutations were found in three families with 21-hydroxylase deficiency. Using DNA sequencing we have identified a novel mutation （P459H） and two rare mutations （A391 T, R483W） of the CYP21 gene. Although microconversion events are the main cause of mutations in the CYP21 gene, random mutations can also be the cause of 21-hydroxylase deficiency.