Altered microRNA expression profiles in large offspring syndrome and Beckwith-Wiedemann syndrome

The use of assisted reproductive technologies (ART) can induce a congenital overgrowth condition in humans and ruminants, namely Beckwith-Wiedemann syndrome (BWS) and large offspring syndrome (LOS), respectively. Shared phenotypes and epigenotypes have been found between BWS and LOS. We have observed global misregulation of transcripts in bovine foetuses with LOS. microRNAs (miRNAs) are important post-transcriptional gene expression regulators. We hypothesize that there is miRNA misregulation in LOS and that this misregulation is shared with BWS. In this study, small RNA sequencing was conducted to investigate miRNA expression profiles in bovine and human samples. We detected 407 abundant known miRNAs and predicted 196 putative miRNAs from the bovine sequencing results and identified 505 abundant miRNAs in human tongue. Differentially expressed miRNAs (DE-miRNAs) were identified between control and LOS groups in all tissues analysed as well as between BWS and control human samples. DE-miRNAs were detected from several miRNA clusters including DLK1-DIO3 genomic imprinted cluster in LOS and BWS. DNA hypermethylation was associated with downregulation of miRNAs in the DLK1-DIO3. mRNA targets of the DE-miRNAs were predicted and signalling pathways associated with control of organ size (including the Hippo signalling pathway), cell proliferation, apoptosis, cell survival, cell cycle, and cell adhesion were found to be enriched with these genes. Yes associated protein 1 (YAP1) is the core effector of the Hippo signalling pathway, and increased level of active (non-phosphorylated) YAP1 protein was detected in skeletal muscle of LOS foetuses. Overall, our data provide evidence of miRNA misregulation in LOS and BWS.

辅助生殖技术（assisted reproductive technologies, ART）可分别在人类和反刍动物中诱发先天性过度生长疾病，即贝威综合征（Beckwith-Wiedemann syndrome, BWS）与巨胎综合征（large offspring syndrome, LOS）。研究发现BWS与LOS存在共有的表型与表观基因型。本团队在罹患LOS的牛胎儿中观察到转录本的全局失调。微小RNA（microRNAs, miRNAs）是重要的转录后基因表达调控因子，我们提出假设：LOS中存在miRNA失调，且该失调模式与BWS共享。本研究通过小RNA测序（small RNA sequencing）探究牛与人类样本中的miRNA表达谱。牛测序结果中共检测到407种丰度较高的已知miRNA，并预测得到196种潜在miRNA；人类舌组织样本中则鉴定出505种高丰度miRNA。在所有分析的组织中，对照组与LOS组之间，以及BWS患者样本与健康对照人类样本之间，均鉴定出差异表达miRNAs（differentially expressed miRNAs, DE-miRNAs）。研究在LOS和BWS样本中，于包括DLK1-DIO3基因组印记簇在内的多个miRNA簇中检测到DE-miRNAs。DLK1-DIO3区域的DNA高甲基化与miRNA的下调存在关联。研究还预测了DE-miRNAs的mRNA靶基因，并发现这些靶基因显著富集于器官大小调控（包括Hippo信号通路）、细胞增殖、凋亡、细胞存活、细胞周期及细胞黏附等相关信号通路。Yes相关蛋白1（Yes associated protein 1, YAP1）是Hippo信号通路的核心效应因子，本研究在LOS胎儿的骨骼肌中检测到活性（非磷酸化）YAP1蛋白水平升高。综上，本研究数据为LOS和BWS中存在miRNA失调提供了实证支持。