Katikala Lavanya, Guruju Mallikarjuna R, Madireddi Sujatha, Vallamkonda Omsairamesh, Vallamkonda Nagaratna, Persha Amarjyothi, Spurgeon Anandaraj M P J
Institute of Genetics and Hospital for Genetic Diseases, Osmania University, Hyderabad, Andhra Pradesh, India.
Genet Test Mol Biomarkers. 2011 Apr;15(4):281-4. doi: 10.1089/gtmb.2010.0167. Epub 2011 Jan 23.
Fragile X syndrome is one of the X-linked disorders associated with moderate to severe mental retardation. Fragile X A syndrome (FRAXA) and fragile X E syndrome (FRAXE) are caused by trinucleotide repeat expansion of CGG and GCC repeats at the 5' untranslated region of the FMR1 and FMR2 genes, respectively. The present study was undertaken to identify the repeat polymorphism and to estimate the risk of transmission in Andhra Pradesh and surrounding states of South India.
The FRAXA and FRAXE allelic polymorphisms were studied by radioactive polymerase chain reaction that revealed 25 FRAXA among 344 X-chromosomes and 20 FRAXE allelic variants among 212 X-chromosomes in our population. The most frequent FRAXA allele size was of 29 CGG repeats (27.5%) followed by allele sizes of 28 (20.8%) and 31 (7.2%), and that of FRAXE was 15 GCC repeats (24.0%) followed by allele containing 18 repeats (18.4%) and 16 repeats (11.3%).
CGG/GCC repeat polymorphism at the FMR1 and FMR2 loci observed in this study demonstrated a racial and ethnic variation among the populations.
脆性X综合征是与中度至重度智力迟钝相关的X连锁疾病之一。脆性X A综合征（FRAXA）和脆性X E综合征（FRAXE）分别由FMR1和FMR2基因5'非翻译区的CGG和GCC三核苷酸重复序列扩增引起。本研究旨在确定印度南部安得拉邦及周边邦的重复序列多态性，并评估其传递风险。
通过放射性聚合酶链反应研究了FRAXA和FRAXE等位基因多态性，结果显示在我们的人群中，344条X染色体中有25条FRAXA，212条X染色体中有20条FRAXE等位基因变体。最常见的FRAXA等位基因大小为29个CGG重复序列（27.5%），其次是28个（20.8%）和31个（7.2%）；FRAXE最常见的等位基因大小为15个GCC重复序列（24.0%），其次是含18个重复序列的等位基因（18.4%）和16个重复序列的等位基因（11.3%）。
本研究中观察到的FMR1和FMR2基因座的CGG/GCC重复序列多态性表明不同人群之间存在种族和民族差异。
