Li Mei-rong, Pan Hong, Bao Xin-hua, Cao Guang-na, Wu Xi-ru
Department of Pediatrics, Peking University First Hospital, Beijing 100034, China.
Zhonghua Er Ke Za Zhi. 2007 Aug;45(8):579-82.
Rett syndrome (RTT, MIM 312750) is a progressive neurodevelopmental disorder that affects females almost exclusively, caused by mutations in MECP2 gene on chromosome Xq28, with symptoms such as autism, severe mental deficiency, deceleration of head growth, ataxia, loss of purposeful hand function and characteristic stereotypic hand movements. Over 80% MECP2 mutations located in the exon 3 and exon 4 were confirmed by our work and large-scale studies. RTT is defined based on clinical presentation. It is difficult to diagnose in the early life without definite biochemical abnormality, but genetic test is helpful for this. The aim of this study was to investigate the feasibility and clinical significance of applying long range polymerase chain reaction (PCR) to RTT diagnosis and establish a simple, economic, efficient method of genetic diagnosis.
Genomic DNA was extracted using standard procedures from the peripheral blood leukocytes of each patient. Long range polymerase chain reaction(PCR)and DNA direct sequencing were employed to analyze the exon 3 and 4 of MECP2 gene simultaneity in 40 patients with RTT. The PCR products were checked by using 1.5% agarose gel.
In total, 18 different MECP2 mutations were identified in 33 of the 40 diagnosed sporadic female patients with RTT. Missense mutations were 16, followed by 14 nonsense mutations and 3 deletions. The 314 base pairs large deletion was identified. The p. T158M mutation (21%, 7/33) was the most common, followed in order of frequency by p. R255X (12%, 4/33), p. R168X and p. R106W (9%, 3/33) respectively, p. R270X and p. Y141X (6%, 2/33) respectively, p. R133C, p. D156H, p. P157L, p. P225R, p. Q244X, p. Q262X, p. R294X, p. R306C, P322L, c. 1005del G, c.1005-1318del 314 bp and c.1127-1179del 53 bp (3%, 1/33), respectively.
Long range PCR is a simple, economic, quick, precise method of genetic diagnosis and was able to find 83% MECP2 gene mutations in RTT patients in this study. It is helpful for RTT clinical diagnosis in early stage. On the other hand, it may detect recurrent mutations and large deletions at the same time.
雷特综合征（RTT，MIM 312750）是一种进行性神经发育障碍，几乎仅影响女性，由X染色体q28上的MECP2基因突变引起，具有如自闭症、严重智力缺陷、头围生长减速、共济失调、目的性手部功能丧失及特征性刻板手部动作等症状。我们的研究及大规模研究证实，超过80%的MECP2突变位于外显子3和外显子4。RTT基于临床表现进行定义。在早期生命阶段若无明确的生化异常则难以诊断，但基因检测对此有帮助。本研究的目的是探讨应用长片段聚合酶链反应（PCR）进行RTT诊断的可行性及临床意义，并建立一种简单、经济、高效的基因诊断方法。
采用标准程序从每位患者的外周血白细胞中提取基因组DNA。运用长片段聚合酶链反应（PCR）和DNA直接测序法同时分析40例RTT患者的MECP2基因外显子3和4。PCR产物用1.5%琼脂糖凝胶进行检测。
在40例确诊的散发型女性RTT患者中，共33例鉴定出18种不同的MECP2突变。错义突变16种，其次为无义突变14种及缺失突变3种。鉴定出314个碱基对的大片段缺失。p.T158M突变（21%，7/33）最为常见，其次依次为p.R255X（12%，4/33）、p.R168X和p.R106W（均为9%，3/33）、p.R270X和p.Y141X（均为6%，2/33）、p.R133C、p.D156H、p.P157L、p.P225R、p.Q244X、p.Q262X、p.R294X、p.R306C、P322L、c.1005del G、c.1005 - 1318del 314 bp和c.1127 - 1179del 53 bp（均为3%，1/33）。
长片段PCR是一种简单、经济、快速、精确的基因诊断方法，在本研究中能够发现83%的RTT患者的MECP2基因突变。它有助于RTT的早期临床诊断。另一方面，它可同时检测复发性突变和大片段缺失。
