Transient Accumulation of 5-Carboxylcytosine Indicates Involvement of Active Demethylation in Lineage Specification of Neural Stem Cells
Transient Accumulation of 5-Carboxylcytosine Indicates Involvement of Active Demethylation in Lineage Specification of Neural Stem Cells
复制标题
DOI：
10.1016/j.celrep.2014.05.003
复制
发表时间：
2014-06-12
期刊：
影响因子：
8.8
通讯作者：
Ruzov, Alexey
中科院分区：
文献类型：
--
作者：
Wheldon, Lee M.;Abakir, Abdulkadir;Ruzov, Alexey
5-甲基胞嘧啶(5mC)是一种表观遗传修饰，参与了分化过程中基因活性的调节。Tet双加氧酶将5mC氧化成5-羟甲基胞嘧啶(5hmC)、5-甲酰胞嘧啶(5fC)和5-羧基胞嘧啶(5caC)。5fC和5caC都可以被胸腺嘧啶-DNA糖基酶(TDG)从DNA中移除，然后通过碱基切除修复途径再生未修饰的胞嘧啶。尽管有证据表明这一机制在胚胎干细胞中是可行的，但依赖TDG的去甲基化在分化和发育中的作用目前尚不清楚。在这里，我们证明了在移植后的小鼠胚胎中发生了广泛的5HmC到5CaC的氧化。我们发现，在培养和体内神经干细胞(NSCs)的谱系确定过程中，5fC和5caC是瞬时积累的。此外，在NSCs分化过程中，5caC在细胞类型特异性启动子处富含，而TDG基因敲除导致NSCs分化过程中5fC/5caC水平升高。我们的数据表明，主动去甲基化有助于决定胚胎大脑的谱系特征的表观遗传重编程。
5-Methylcytosine (5mC) is an epigenetic modification involved in regulation of gene activity during differentiation. Tet dioxygenases oxidize 5mC to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC). Both 5fC and 5caC can be excised from DNA by thymine-DNA glycosylase (TDG) followed by regeneration of unmodified cytosine via the base excision repair pathway. Despite evidence that this mechanism is operative in embryonic stem cells, the role of TDG-dependent demethylation in differentiation and development is currently unclear. Here, we demonstrate that widespread oxidation of 5hmC to 5caC occurs in postimplantation mouse embryos. We show that 5fC and 5caC are transiently accumulated during lineage specification of neural stem cells (NSCs) in culture and in vivo. Moreover, 5caC is enriched at the cell-type-specific promoters during differentiation of NSCs, and TDG knockdown leads to increased 5fC/5caC levels in differentiating NSCs. Our data suggest that active demethylation contributes to epigenetic reprogramming determining lineage specification in embryonic brain.