Select microRNAs are essential for early development in the sea urchin.

microRNAs (miRNAs) are small noncoding RNAs that mediate post-transcriptional gene regulation and have emerged as essential regulators of many developmental events. The transcriptional network during early embryogenesis of the purple sea urchin, Strongylocentrotus purpuratus, is well described and would serve as an excellent model to test functional contributions of miRNAs in embryogenesis. We examined the loss of function phenotypes of the major components of the miRNA biogenesis pathway. Inhibition of de novo synthesis of Drosha and Dicer in the embryo led to consistent developmental defects, a failure to gastrulate, and embryonic lethality, including changes in the steady state levels of transcription factors and signaling molecules involved in germ layer specification. We annotated and profiled small RNA expression from the ovary and several early embryonic stages by deep sequencing followed by computational analysis. All miRNAs have dynamic accumulation profiles through early development as do a large population of putative piRNAs (piwi-interacting RNAs). Defects in morphogenesis caused by loss of Drosha can be rescued with four miRNAs which permits a strong miRNA functional assay. Taken together our results indicate that post-transcriptional gene regulation directed by miRNAs is functionally important for early embryogenesis and is an integral part of the early embryonic gene regulatory network in S. purpuratus. Small RNA expression profiling in early sea urchin development

微小RNA（microRNAs，miRNAs）是一类小型非编码RNA，可介导转录后基因调控，现已成为众多发育事件的关键调控因子。紫色海胆（Strongylocentrotus purpuratus）早期胚胎发生过程中的转录调控网络已有充分研究，可作为检测miRNAs在胚胎发生中功能贡献的优秀模型。本研究针对miRNA生成通路的主要组分开展了功能缺失表型分析：在胚胎中抑制Drosha与Dicer的从头合成，会引发一致的发育缺陷、原肠胚形成失败及胚胎致死，同时还会改变参与胚层特化的转录因子与信号分子的稳态水平。本研究通过深度测序结合计算分析，对卵巢及多个早期胚胎阶段的小RNA表达进行了注释与表达谱分析。结果显示，所有miRNAs在早期发育过程中均呈现动态积累模式，大量推定的piwi相互作用RNA（piwi-interacting RNAs，piRNAs）亦是如此。敲低Drosha所导致的形态发生缺陷可通过四种miRNAs得以挽救，这一体系可用于开展严谨的miRNA功能验证实验。综合以上结果，本研究表明由miRNAs介导的转录后基因调控对紫色海胆早期胚胎发生具有重要功能意义，是S. purpuratus早期胚胎基因调控网络的不可或缺的组成部分。海胆早期发育中的小RNA表达谱分析