Özer Leyla, Ruhi Hatice Ilgın, Bökesoy Işık
Mikrogen Genetic Diagnosis Center, Ankara, Turkey.
Division of Medical Genetics, Faculty of Medicine, Ankara University, Ankara, Turkey.
Genome Integr. 2020 Aug 13;11:1. doi: 10.4103/genint.genint_4_20. eCollection 2020.
Chromosome fragile sites tend to form gap or break in chromosomes when the cells are exposed to replication stress. Folic acid deprivation in the culture medium induces folate-sensitive rare fragile sites, such as FRAXA which is responsible for the fragile X mental retardation syndrome. Chromosome instability at fragile sites can be evaluated by biomarkers of genomic instability such as frequency of micronuclei (MN). It was aimed to analyse the chromosome content of MN in Fragile X cells during folate deprivation by the MN-fluorescence in situ hybridization (FISH) method. Samples from five Fragile X syndrome patients, diagnosed using cytogenetic and molecular methods, as well as from their parents and five controls were included in the study. Blood samples were cultured in two different culture media (folate-deficient and normal). Results of MN-FISH test were analysed in terms of MN frequency and chromosome content of MN. An accumulation of MN in Fragile X patients, mainly containing T (+) or C (+) MN or T (+) plus C (+) MN in binucleated cells was found. Finally, MN-FISH analysis allowed confirming that the increase in MN frequency is due to a higher sensitivity to chromosome breakage along the X chromosome.
当细胞暴露于复制应激时，染色体脆弱位点往往会在染色体上形成缺口或断裂。培养基中叶酸缺乏会诱导叶酸敏感的罕见脆弱位点，如导致脆性X智力障碍综合征的FRAXA。脆弱位点处的染色体不稳定性可通过基因组不稳定性的生物标志物如微核（MN）频率来评估。本研究旨在通过MN-荧光原位杂交（FISH）方法分析叶酸缺乏期间脆性X细胞中MN的染色体组成。研究纳入了5名经细胞遗传学和分子方法诊断的脆性X综合征患者及其父母的样本，以及5名对照。血液样本在两种不同的培养基（叶酸缺乏和正常）中培养。根据MN频率和MN的染色体组成分析MN-FISH测试结果。发现脆性X患者中MN积累，主要在双核细胞中含有T（+）或C（+）MN或T（+）加C（+）MN。最后，MN-FISH分析证实MN频率的增加是由于对X染色体上染色体断裂的更高敏感性。
