Neuroscience Graduate Program, University of California, San Francisco, CA 94158, USA.
Proc Natl Acad Sci U S A. 2013 Sep 3;110(36):14682-7. doi: 10.1073/pnas.1302759110. Epub 2013 Aug 22.
The modified DNA base 5-hydroxymethylcytosine (5hmC) is enriched in neurons where it may contribute to gene regulation and cellular identity. To determine how 5hmC influences gene expression in an in vivo neuronal population, we assessed the patterning and function of the base along the developmental lineage of the main olfactory epithelium-from multipotent stem cells through neuronal progenitors to mature olfactory sensory neurons (mOSNs). We find that 5hmC increases over gene bodies during mOSN development with substantial patterning occuring between the progenitor and mOSN stages. Although gene-body 5hmC levels correlate with gene expression in all three developmental cell types, this association is particularly pronounced within mOSNs. Overexpression of Tet3 in mOSNs markedly alters gene-body 5hmC levels and gene expression in a manner consistent with a positive role for 5hmC in transcription. Moreover, Tet3 overexpression disrupts olfactory receptor expression and the targeting of axons to the olfactory bulb, key molecular and anatomical features of the olfactory system. Our results suggest a physiologically significant role for gene-body 5hmC in transcriptional facilitation and the maintenance of cellular identity independent of its function as an intermediate to demethylation.
经修饰的 DNA 碱基 5-羟甲基胞嘧啶（5hmC）在神经元中富集，可能有助于基因调控和细胞身份。为了确定 5hmC 如何在体内神经元群体中影响基因表达，我们评估了其沿着主要嗅觉上皮细胞的发育谱系的模式和功能 - 从多能干细胞到神经元祖细胞再到成熟的嗅觉感觉神经元（mOSN）。我们发现，5hmC 在 mOSN 发育过程中在基因体上增加，在祖细胞和 mOSN 阶段之间发生了大量的模式形成。尽管基因体 5hmC 水平与所有三种发育细胞类型的基因表达相关，但这种关联在 mOSN 中尤为明显。Tet3 在 mOSN 中的过表达显著改变了基因体 5hmC 水平和基因表达，这与 5hmC 在转录中发挥积极作用一致。此外，Tet3 的过表达破坏了嗅觉受体的表达和轴突向嗅球的靶向，这是嗅觉系统的关键分子和解剖特征。我们的结果表明，基因体 5hmC 在转录促进和细胞身份维持方面具有生理上显著的作用，独立于其作为去甲基化中间物的功能。
