Department of Molecular Biology and Functional Genomics, Stockholm University, Stockholm 10691, Sweden.
Hum Mol Genet. 2012 Jan 15;21(2):311-21. doi: 10.1093/hmg/ddr461. Epub 2011 Oct 7.
Schizophrenia and bipolar disorder (BPD) are common neurodevelopmental disorders, characterized by various life-crippling symptoms and high suicide rates. Multiple studies support a strong genetic involvement in the etiology of these disorders, although patterns of inheritance are variable and complex. Adenosine-to-inosine RNA editing is a cellular mechanism, which has been implicated in mental disorders and suicide. To examine the involvement of altered RNA editing in these disorders, we: (i) quantified the mRNA levels of the adenosine deaminase acting on RNA (ADAR) editing enzymes by real-time quantitative polymerase chain reaction, and (ii) measured the editing levels in transcripts of several neuroreceptors using 454 high-throughput sequencing, in dorsolateral-prefrontal cortices of schizophrenics, BPD patients and controls. Increased expression of specific ADAR2 variants with diminished catalytic activity was observed in schizophrenia. Our results also indicate that the I/V editing site in the glutamate receptor, ionotropic kainate 2 (GRIK2) transcript is under-edited in BPD (type I) patients (45.8 versus 53.9%, P= 0.023). GRIK2 has been implicated in mood disorders, and editing of its I/V site can modulate Ca(+2) permeability of the channel, consistent with numerous observations of elevated intracellular Ca(+2) levels in BPD patients. Our findings may therefore, at least partly, explain a molecular mechanism underlying the disorder. In addition, an intriguing correlation was found between editing events on separate exons of GRIK2. Finally, multiple novel editing sites were detected near previously known sites, albeit most with very low editing rates. This supports the hypothesis raised previously regarding the existence of wide-spread low-level 'background' editing as a mechanism that enhances adaptation and evolvability.
精神分裂症和双相情感障碍（BPD）是常见的神经发育障碍，其特征是各种致残症状和高自杀率。多项研究支持这些疾病的病因与遗传因素密切相关，尽管遗传模式是可变且复杂的。腺苷到肌苷 RNA 编辑是一种细胞机制，已被认为与精神障碍和自杀有关。为了研究改变的 RNA 编辑是否参与这些疾病，我们：（i）通过实时定量聚合酶链反应定量测定 ADAR 编辑酶的 mRNA 水平，（ii）使用 454 高通量测序测量精神分裂症、BPD 患者和对照组背外侧前额叶皮质中几种神经受体的转录本的编辑水平。在精神分裂症中观察到特定 ADAR2 变体的表达增加，但其催化活性降低。我们的结果还表明，BPD（I 型）患者谷氨酸受体、离子型 kainate 2（GRIK2）转录本中的 I/V 编辑位点编辑不足（45.8%对 53.9%，P=0.023）。GRIK2 与心境障碍有关，其 I/V 位点的编辑可以调节通道的 Ca(+2)通透性，这与 BPD 患者细胞内 Ca(+2)水平升高的许多观察结果一致。因此，我们的发现至少可以部分解释这种疾病的潜在分子机制。此外，还发现 GRIK2 上不同外显子的编辑事件之间存在有趣的相关性。最后，尽管大多数编辑率非常低，但在先前已知的位点附近检测到多个新的编辑位点。这支持了先前提出的关于广泛存在低水平“背景”编辑作为增强适应和可进化性的机制的假设。
