MECP2 Promoter Methylation and X Chromosome Inactivation in Autism
MECP2 Promoter Methylation and X Chromosome Inactivation in Autism
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DOI：
10.1002/aur.24
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发表时间：
2008-06-01
期刊：
影响因子：
4.7
通讯作者：
LaSalle, Janine M.
中科院分区：
文献类型：
--
作者：
Nagarajan, Raman P.;Patzel, Katherine A.;LaSalle, Janine M.
表观遗传机制已被提出在自闭症的病因学中发挥作用。这一假设得到了以下发现的支持：在自闭症男性大脑中，MECP2启动子甲基化增加与MeCP2蛋白表达减少相关。为了进一步了解女性X染色体失活（XCI）和邻近甲基化模式对自闭症患者异常MECP 2启动子甲基化的影响，对自闭症患者的大脑和血液样本进行了多重甲基化分析。亚硫酸氢盐测序分析的区域0.6 kb的MECP2在脑DNA样品的上游，揭示了一个突然的过渡，从一个高度甲基化的区域在两种性别的男性和受XCI在女性的区域未甲基化。染色质免疫沉淀分析表明，CCCTC结合因子（CTCF）结合到这个过渡区的神经元细胞，在甲基化过渡的染色质边界一致。男性自闭症大脑DNA样本在这个过渡区域显示甲基化略有增加，这表明甲基化可能异常扩散到自闭症男性的MECP2启动子中。此外，自闭症女性脑DNA样品显示异常MECP 2启动子甲基化的证据，因为亚硫酸氢盐测序的克隆的数量都增加，其中MECP 2而不是雄激素受体（AR）的XCI状态不确定。为了进一步研究自闭症中MECP2甲基化改变的特异性，还检查了来自患有自闭症的女性和男性的母亲的血液DNA样品在AR处的XCI偏斜，但与对照相比，没有观察到XCI偏斜的显著增加。这些结果表明，自闭症大脑DNA样本中的异常MECP2甲基化是由于基因座特异性而不是整体X染色体甲基化变化。
Epigenetic mechanisms have been proposed to play a role in the etiology of autism. This hypothesis is supported by the discovery of increased MECP2 promoter methylation associated with decreased MeCP2 protein expression in autism male brain. To further understand the influence of female X chromosome inactivation (XCI) and neighboring methylation patterns on aberrant MECP2 promoter methylation in autism, multiple methylation analyses were performed on brain and blood samples from individuals with autism. Bisulfite sequencing analyses of a region 0.6 kb upstream of MECP2 in brain DNA samples revealed an abrupt transition from a highly methylated region in both sexes to a region unmethylated in males and subject to XCI in females. Chromatin immunoprecipitation analysis demonstrated that the CCCTC-binding factor (CTCF) is bound to this transition region in neuronal cells, consistent with a chromatin boundary at the methylation transition. Male autism brain DNA samples displayed a slight increase in methylation in this transition region, suggesting a possible aberrant spreading of methylation into the MECP2 promoter in autism males across this boundary element. In addition, autistic female brain DNA samples showed evidence for aberrant MECP2 promoter methylation as ail increase in the number of bisulfite sequenced clones with undefined XCI status for MECP2 but not androgen receptor (AR). To further investigate the specificity of MECP2 methylation alterations in autism, blood DNA samples from females and mothers of males with autism were also examined for XCI skewing at AR, but no significant increase in XCI skewing was observed compared to controls. These results suggest that the aberrant MECP2 methylation in autism brain DNA samples is due to locus-specific rather than global X chromosome methylation changes.