佩梅样病3家系临床及分子遗传学研究

Clinical and molecular genetic analysis of three pedigrees with Pelizaeus.Merzbacher-like disease

目的分析并确定佩梅样病（Pelizaeus-Merzbacher-like disease，PMLD）3个家系的临床及分子遗传学特点，为PMLD患者家庭提供准确的遗传咨询及产前检查打基础。方法2010年5月至2013年3月北京大学第一医院儿科收集3个家系4例（P1-4）PMLD男性患儿及其家系成员临床资料，其中P1与P2为表型相似的同胞兄弟，进行临床特点分析：包括病史、体征、辅助检查特点；应用聚合酶链反应和DNA直接测序方法进行缝隙连接蛋白gamma-2基因（GJC2）与蛋白脂蛋白1基因（PLP1）突变检测，采用多重连接依赖的探针扩增技术（MLPA）检测PLPl重复突变，明确基因突变类型，进行分子遗传学特点分析。结果1．临床特点：4例患儿均具有共济失调以及头颅磁共振成像（MRI）脑白质髓鞘化不良特点，P1-3主要于婴儿期发病，以眼球震颤为首发症状，均表现为精神运动发育落后、肌张力低下。P4于8岁7个月以手抖、听力下降发病，根据临床特征及头颅MRI表现P1-4均符合临床诊断PMLD。2．遗传学特点：4例PMLD患儿共发现GJC25种核苷酸改变：c．579delC（P．Glyl93fsXl7）、c．1296-1297insG（P．Gly433fsX59）、c．735C〉A（P．Cys245X）、c．689delG（P．Gly230AlafsX241）与c．1199C〉A（P．Ala400Glu），均为国际上未报道的新突变。P1-3均为复合杂合突变致病，分别遗传自表型正常的父母；P4发现GJC2c．1199C〉A（P．Ala400Glu）纯合突变，表型正常P4之父为本位点的杂合改变，母亲在本位点为野生型。结论本研究3个家系4例PMLD患儿临床表现均符合PMLD的特点，PMLD临床诊断成立。GJC2分析发现了5种突变均为国际上尚未报道的新突变，扩展了GJC2的突变谱。明确了PMLD3个家系临床与分子遗传学特征，为准确的遗传咨询和进一步的产前诊断打下了基础。

Objective To analyze the clinical and molecular genetic features in 3 pedigrees with Pelizaeus- Merzbacher-like disease （PMLD） ,thus providing a better genetic counseling and correct prenatal diagnosis for those families with PMLD. Methods Clinical data of 4 male pediatric patients （P1-4） and their family members in 3 pedi- grees with PMLD were collected from May,2010 to Mar. 2013 in Department of Pediatrics, Peking University First Hos- pital, including medical history, physical signs, and auxiliary examinations. For 4 pediatric patients, P1 and P2 were sib- lings with similar clinical manifestations. Polymerase chain reaction and sequence analysis of DNA were performed to determine the gene mutation of gap junction protein gamma-2（GJC2） and proteolipid protein 1 （PLP1） ,and multiplex ligation-dependent probe amplification was utilized to detect PLP1 duplication. With these detection methods, the gene mutations were confirmed, and then genetic features were analyzed. Results 1. Clinical features： Four patients with PMLD showed ataxia and hypomyelination abnormalities from brain nuclear magnetic resonance imaging（MRI）. Ages of onset were mainly in infants for P1-3, and 8 years old and 7 months for P4. Nystagmus was the first symptom for P1-3 while hands shaking and hearing loss for P4. Psychomotor development delay and hypotonia were observed in all of P1- 3. The clinical data and brain MRI of 4 patients were all in conformity with the clinical diagnosis standards of PMLD. 2. Genetic Features： five novel GJC2 mutations, including c. 579delC （ p. Gly193fsX17 ）, c. 1296_ 1297insG （ p. Gly433fsX59）, c. 735C 〉 A （ p. Cys245X）, c. 689delG （ p. Gly230AlafsX241 ）, and c. 1199C 〉 A （ p. Ala400Glu） were found in 4 patients,which had never been reported home and abroad. P1-3 showed a compound hete-rozygous mu- tation, which were inherited from their parents with normal phenotype. And c. 1199C 〉 A （ p. Ala4OOGlu） homozygous mutation in GJC2 was detected from P4, and their fathers and mothers, heterozygous variation and wild type were found in the corresponding locus, respectively. Conclusions Four patients from 3 pedigrees were diagnosed as PMLD clini- cally based on their clinical data. Five novel GJC2 mutations were found in this study. Therefore, the spectrum of GJC2 mutations will be expanded. In addition, this study elucidated the clinical and genetic characteristics of 3 pedigrees with PMLD, which would lay a solid foundation for the correct genetic counseling and prenatal diagnosis for those pedigrees.