Centre for Vision and Vascular Science, Queen's University Belfast, Northern Ireland, UK.
BMC Genomics. 2012 Aug 1;13:357. doi: 10.1186/1471-2164-13-357.
MicroRNAs (miRNAs) are a class of small RNA molecules that regulate expression of specific mRNA targets. They can be released from cells, often encapsulated within extracellular vesicles (EVs), and therefore have the potential to mediate intercellular communication. It has been suggested that certain miRNAs may be selectively exported, although the mechanism has yet to be identified. Manipulation of the miRNA content of EVs will be important for future therapeutic applications. We therefore wished to assess which endogenous miRNAs are enriched in EVs and how effectively an overexpressed miRNA would be exported.
Small RNA libraries from HEK293T cells and vesicles before or after transfection with a vector for miR-146a overexpression were analysed by deep sequencing. A subset of miRNAs was found to be enriched in EVs; pathway analysis of their predicted target genes suggests a potential role in regulation of endocytosis. RT-qPCR in additional cell types and analysis of publicly available data revealed that many of these miRNAs tend to be widely preferentially exported. Whilst overexpressed miR-146a was highly enriched both in transfected cells and their EVs, the cellular:EV ratios of endogenous miRNAs were not grossly altered. MiR-451 was consistently the most highly exported miRNA in many different cell types. Intriguingly, Argonaute2 (Ago2) is required for miR-451 maturation and knock out of Ago2 has been shown to decrease expression of other preferentially exported miRNAs (eg miR-150 and miR-142-3p).
The global expression data provided by deep sequencing confirms that specific miRNAs are enriched in EVs released by HEK293T cells. Observation of similar patterns in a range of cell types suggests that a common mechanism for selective miRNA export may exist.
MicroRNAs（miRNAs）是一类调节特定 mRNA 靶标表达的小 RNA 分子。它们可以从细胞中释放出来，通常被包裹在细胞外囊泡（EVs）中，因此具有介导细胞间通讯的潜力。有人提出某些 miRNAs 可能会被选择性地输出，尽管其机制尚未确定。对 EVs 中 miRNA 含量的操纵对于未来的治疗应用将非常重要。因此，我们希望评估哪些内源性 miRNAs 在 EVs 中富集，以及过表达的 miRNA 被有效地输出的效率。
通过深度测序分析了 HEK293T 细胞和转染 miR-146a 过表达载体前后的 EVs 中的小 RNA 文库。发现一小部分 miRNA 在 EVs 中富集；其预测靶基因的途径分析表明，它们可能在调节内吞作用中发挥作用。在其他细胞类型中的 RT-qPCR 和对公开可用数据的分析表明，这些 miRNA 中的许多都倾向于广泛优先输出。虽然过表达的 miR-146a 在转染细胞及其 EVs 中都高度富集，但内源性 miRNA 的细胞：EV 比值并未发生明显改变。miR-451 在许多不同的细胞类型中始终是最优先输出的 miRNA。有趣的是，Argonaute2（Ago2）是 miR-451 成熟所必需的，Ago2 的敲除已被证明会降低其他优先输出的 miRNA（如 miR-150 和 miR-142-3p）的表达。
深度测序提供的全局表达数据证实，特定的 miRNAs 在 HEK293T 细胞释放的 EVs 中富集。在多种细胞类型中观察到相似的模式表明，可能存在一种用于选择性 miRNA 输出的共同机制。
