MicroRNAs are small noncoding RNAs that are important for proper cardiac development. In our previous study of fetuses with ventricular septal defects, we discovered that microRNA-375 (miR-375) is obviously upregulated compared with that in healthy controls. Our study also confirmed that miR-375 is crucial for cardiomyocyte differentiation. This research mainly focused on the biological significance and mechanism of miR-375 using a zebrafish model. We injected zebrafish embryos with 1–2 nl of a miR-375 mimic at various concentrations (0/2/4/8 μM) or with negative control. The deformation and mortality rates were separately assessed. The different expression levels of miR-375 and related genes were examined by qRT-PCR, and luciferase assays and in situ hybridization were used to clarify the mechanism of miR-375 during embryonic development. Overexpression of miR-375 disrupted the cardiac development of zebrafish embryos. Disruption of miR-375 led to a decreased heart rate, pericardial edema, and abnormal cardiac looping. Various genes involved in cardiac development were downregulated due to the overexpression of miR-375. Moreover, the NOTCH signaling pathway was affected, and the luciferase reporter gene assays confirmed notch2, which was predicted by bioinformatics analysis, as the target gene of miR-375. Our findings demonstrated that the overexpression of miR-375 is detrimental to embryonic development, including cardiac development, and can partially simulate a multisystemic disorder. MiR-375 has an important role during cardiac morphogenesis of zebrafish embryos by targeting notch2, indicating its potential as a diagnostic marker.

中文翻译：

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MicroRNA-375 过表达通过靶向 Notch2 破坏斑马鱼 (Danio rerio) 的心脏发育

MicroRNA 是小的非编码 RNA，对心脏的正常发育很重要。在我们之前对室间隔缺损胎儿的研究中，我们发现与健康对照组相比，microRNA-375 (miR-375) 明显上调。我们的研究还证实 miR-375 对心肌细胞分化至关重要。本研究主要利用斑马鱼模型研究miR-375的生物学意义和机制。我们向斑马鱼胚胎注射了 1-2 nl 不同浓度 (0/2/4/8 μM) 的 miR-375 模拟物或阴性对照。分别评估变形率和死亡率。通过qRT-PCR检测miR-375及相关基因的不同表达水平，并通过荧光素酶测定和原位杂交阐明miR-375在胚胎发育过程中的作用机制。miR-375 的过表达破坏了斑马鱼胚胎的心脏发育。miR-375 的破坏导致心率降低、心包水肿和心脏循环异常。由于miR-375的过表达，参与心脏发育的各种基因被下调。此外，NOTCH信号通路受到影响，荧光素酶报告基因检测证实了生物信息学分析预测的notch2是miR-375的靶基因。我们的研究结果表明，miR-375 的过表达对胚胎发育（包括心脏发育）有害，并且可以部分模拟多系统疾病。MiR-375 通过靶向 Notch2 在斑马鱼胚胎的心脏形态发生过程中发挥重要作用，表明其作为诊断标志物的潜力。