استخدام تقنية التفاعل السلسلي للبوليميراز PCR لكشف الأليل المتوسع لجين هشاشة الصبغي X (FMR1)‎

الملخص EN

Fragile X syndrome is the most common cause of inherited mental retardation, and that results from the expansion of CGG repeats in the 5' untranslated region of FMR1 gene, located on the long arm of X chromosome at Xq27.3.

while, the number of CGG triple repeats for normal people do not exceed (45 repeats), but the number of CGG repeats can reach more than 200 repeats in fragile X affected people.

Our aim of this study is to apply a quick and inexpensive technique to diagnose fragile X syndrome, in order to detect the CGG allele expansion of FMR1 gene in patients.

In addition of providing diagnosis, especially among families who have a family history of this syndrome, by using this technique which is applied for the first time in Syria and it is established for deeper molecular genetics studies in the future.

We used specific primers to amplify the CGG triple repeat region of FMR1 gene by using the PCR technique on ten patients (males and females), who are clinically diagnosed as affected fragile X patients.

Our results showed two patients having Mosaicism of CGG repeats, the first patient had two types of CGG repeats , the first type was normal repeat, it was about (42 repeats) and the second type was premutation and it was about (170 repeats).

The second patient showed two types of triple CGG repeats, the first type was full mutation and the number of CGG repeats was (442 repeats), the second type was premutation (177 repeats).

In the rest of cases which we studied, the number of repeats were within the normal level, ranging between 29 – 37 repeats.

Though these results we concluded, the PCR technique is important in detection and diagnosis the fragile X syndrome, also it is sensitive and accurate technique especially for the detection of the mosaic cases, which can not be detected by using other techniques as cytogenetic (karyotype), in addition it is a quick, inexpensive technique, so it reduces the use of Southern blot, making it the first choice for wide screening population.