Fragile-X Mental Retardation-A Combination of Cytogenetic and Molecular Approaches, with Greater Emphasis on DNA Analysis

X染色體脆折症：合併細胞學及分子生物學之診斷，並強調DNA分析之重要性

王作仁(Tso-Ren Wang) ； 胡務亮(Wuh-Liang Hwu) ； 侯家瑋(Jia-Woei Hou) ； 周西平(Shi-Ping Chou) ； 劉敬萱(Ching-Hsuan Liu)

《Acta Paediatrica Sinica》 34卷2期 (1993/04) Pp. 105-112

摘要

X染色體脆折症是一種極重要的遺傳性智能不足疾病。在過去，X染色體脆折症的診斷主要靠在染色體檢查時找到Xq27.3的脆折點。最近此疾病的基因FMR-1已被篩選出來。本研究即結合染色體及基因的診斷。我首先利用聚合酶鏈反應，以pE5.1為樣本，篩選出pE5.1中的一個小片段pP1fr。以pP1fr為探針，我們以限制酶片段長度多態性，研究兩個經染色體檢查證實的X染色體脆折症家族。
我們發現，以EcoRI多態性診斷X染色體脆折症十分的簡單且準確。若想研究患者基因的甲基化，則可再加上一個對甲基敏感的限制酶BssH Ⅱ。我們同時也進行的PstI多態性分析，並證明患者的片段長度可更精確的和正常人的1kb片段區分。非常明顯的片段鑲崁現象也是多態性之特點。本研究顯示X染色體脆折症的DNA診斷是一項敏感且可靠的方法。

關鍵字

文摘

並列摘要

Fragile X syndrome is one of the most frequent causes of hereditary mental retardation. In the past, its diagnosis depended primarily on cytogenetic demonstration of chromosome fragile site Xq27.3. Recently, the gene FMR-1 has been found responsible for this disease. Here a combined method was used to study fragile X syndrome. A fragment (pP1fr) of DNA was subcloned from pE5.1 by polymerase chain reaction. With this probe, DNA samples from two cytogenetically proved families were analyzed by restriction fragment length polymorphisms. It was demonstrated that EcoRI polymorphism was an easy and accurate method for diagnosis of the fragile X syndrome. To study methylation status of patients, another methylation-sensitive enzyme, BssHⅡ, could be used together with EcoRI. The PstI polymorphism of one family was also studied and showed one kb fragment as normal, and detected more precise changes in length. Prominent mosaicism necessary was characteristic in PstI polymorphism. The DNA diagnosis of fragile X syndrome was a reliable method.

並列關鍵字

marXq27.3 ； polymerase chain reaction ； Southern analysis