神经管畸形患者锌指蛋白ZIC2基因编码区罕见突变的分子遗传分析

目的筛选ZIC2外显子区域基因突变，分析突变对神经管畸形（NTDs）的影响。方法采用病例对照研究方法，收集来自山西省和江苏省苏州市经孕期B超或病理学解剖证实为NTDs的胎儿为NTDs组，以常规体检排除出生缺陷和重大疾病的胎儿和健康成年人为对照组。采用酚-氯仿法抽提基因组DNA，通过PCR扩增ZIC2的3个外显子及邻近的部分内含子序列，扩增产物采用ABI Prism Bigdye system进行测序，对于测序发现的基因突变进行反向测序验证。结果NTDs组163例，对照组576例。在NTDs组中发现一个同义突变c．1140G〉A，未发现错义突变或重复缺失。同义突变c．1140G〉A位于第2外显子，为1例妊娠期37周诊断为枕部脑膜脑膨出的女性胎儿。KEGG数据库分析ZIC2结构发现该同义突变位于ZIC2的一个C2H2锌指结构中。在对照组中未检测到相同突变。结论ZIC2是一个高度保守基因，其编码区不含有与NTDs相关的SNP和罕见突变。

Molecular genetic analysis on rare mutations of ZIC2 coding region in neural tube defects cases

Objective Neural tube defects are severe birth defects, affecting approximately 1 -2 in every 1 000 live births. ZIC2 is a member of ZIC family, which contains 5 zinc finger proteins in mammals. ZIC2 hypomorphic mutant mice show holoprosencephaly. Here ZIC2 exons and flanking sequences were screened for rare mutations in Chinese neural tube defects cases and matched controls. Methods Case group included DNA samples of stillborn fetuses with neural tube defects, which had been confirmed by B ultrasound in gestation and anatomical pathology, from Shanxi and Suzhou, China. Control group consisted of DNA samples of unrelated randomly selected fetuses and adults without serious birth defects or serious illnesses from the same region. Genomic DNA was extracted using phenol-chloroform method. Polymerase chain reaction （PCR） was used to amplify ZIC2 exons from genomic DNA. The PCR products were sequenced by ABI 3730 sequencer through ABI Prism Bigdye system （ABI, Foster City, CA, USA）. Every detected mutation was validated by sequencing from the complementary strand. Results A synonymous mutation c. 1140G 〉 A locating in the second exon of ZIC2 was specifically found in a 37-week gestation female fetus diagnosed with encephalocele. KEGG database showed this mutation was in one C2 H2 finger domain of ZIC2. No missense mutation or insertion/ deletion in ZIC2 coding region was found in neural tube defects cases or controls. Conclusions ZIC2 gene was highly conservative in sequence. No mutations or SNPs in coding region of ZIC2 gene were identified to be associated with neural tube defects in Chinese.