Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
BMC Genomics. 2018 Jun 28;19(1):507. doi: 10.1186/s12864-018-4848-x.
Anuran metamorphosis, which is obligatorily initiated and sustained by thyroid hormone (TH), is a dramatic example of extensive morphological, biochemical and cellular changes occurring during post-embryonic development. Thus, it provides an ideal model to understand the actions of the hormone and molecular mechanisms underlying these developmental and apoptotic processes. In addition to transcriptional factors, microRNAs (miRNAs) play key roles in diverse biological processes via post-transcriptional repression of mRNAs. However, the possible role of miRNAs in anuran metamorphosis is not well understood. Screening and identification of TH-responding miRNAs are required to reveal the integrated regulatory mechanisms of TH during metamorphosis. Given the specific role of TRs during M. fissipes metamorphosis and the characteristics of M. fissipes as an ideal model, Illumina sequencing technology was employed to get a full scope of miRNA in M. fissipes metamorphosis treated by T3.
Morphological and histological analysis revealed that 24 h T3 treatment M. fissipes tadpoles resembled that at the climax of natural metamorphosis. Thus, small RNA libraries were constructed from control and 24 h T3 treatment groups. A total of 164 conserved miRNAs and 36 predicted novel miRNAs were characterized. Furthermore, 5' first and ninth nucleotides of miRNAs were significantly enriched in U in our study. In all, 21 miRNAs were differentially expressed between the T3 and control groups (p < 0.01). A total of 10,206 unigenes were identified as target genes of these differentially expressed miRNAs. KEGG pathway analysis indicated that the most overrepresented miRNA target genes were enriched in the "PI3k-Akt signaling pathway". In addition, a network associated with the TH signaling pathway provides an opportunity to further understand the complex biological processes that occur in metamorphosis.
We identified a large number of miRNAs during M. fissipes metamorphosis, and 21 of them were differentially expressed in the two groups that represented two different metamorphic stages. These miRNAs may play important roles during metamorphosis. The study gives us clues for further studies of the mechanisms of anuran metamorphosis and provides a model to study the mechanism of TH-affected biological processes in humans.
蛙类变态，由甲状腺激素（TH）强制启动并维持，是胚胎后发育过程中广泛的形态、生化和细胞变化的一个显著例子。因此，它提供了一个理想的模型来了解激素的作用以及这些发育和凋亡过程的分子机制。除了转录因子外，miRNA（miRNA）通过对 mRNA 的转录后抑制在多种生物学过程中发挥关键作用。然而，miRNA 在蛙类变态中的可能作用尚未得到很好的理解。筛选和鉴定对 TH 有反应的 miRNA 是揭示 TH 在变态过程中的综合调控机制所必需的。鉴于 TR 在 M. fissipes 变态过程中的特殊作用以及 M. fissipes 作为理想模型的特点，我们采用 Illumina 测序技术在 T3 处理的 M. fissipes 变态过程中获得了 miRNA 的全貌。
形态学和组织学分析表明，24 小时 T3 处理的 M. fissipes 蝌蚪类似于自然变态的高潮期。因此，我们从对照组和 24 小时 T3 处理组构建了小 RNA 文库。共鉴定出 164 个保守 miRNA 和 36 个预测的新 miRNA。此外，在我们的研究中，miRNA 的 5' 第一个和第九个核苷酸显著富集在 U 中。共有 21 个 miRNA 在 T3 组和对照组之间差异表达（p<0.01）。这些差异表达 miRNA 的靶基因总数为 10206 个。KEGG 途径分析表明，最过度表达的 miRNA 靶基因富集在“PI3k-Akt 信号通路”中。此外，与 TH 信号通路相关的网络为进一步了解变态过程中发生的复杂生物学过程提供了机会。
我们在 M. fissipes 变态过程中鉴定了大量的 miRNA，其中 21 个在代表两个不同变态阶段的两组中差异表达。这些 miRNA 可能在变态过程中发挥重要作用。该研究为进一步研究蛙类变态的机制提供了线索，并为研究 TH 影响人类生物过程的机制提供了模型。
