In vivo functions of the long non-coding RNA (lncRNA) Fendrr in cardiac development during mouse embryogenesis

脊椎动物转录组中最丰富的RNA转录物是长非编码RNA（lncRNA），其转录物长于200个核苷酸并且不编码蛋白质。lncRNA与表观遗传变化、发育缺陷和癌症有关，敲除有时是致命的。我们以前的研究表明，lncRNA Fendrr是小鼠胚胎发育所必需的，突变的胚胎由于心脏缺陷而死亡。我们将进一步研究Fendrr在小鼠胚胎早期心脏细胞谱系发育中的分子作用。这项工作将帮助我们了解Fendrr的缺失如何导致心脏缺陷，以及Fendrr如何与多梳抑制复合物2（PRC 2）一起调节心脏特异性基因表达。此外，我们还将鉴定与Fendrr相互作用的其他蛋白质和蛋白质复合物，并分析它们在早期心脏发育中的体内作用。此外，Fendrr转录物的某些元件可以直接与基因组相互作用以调节靶基因表达，并最终帮助将蛋白质复合物募集到基因组中的特定位点。我们在Fendrr的记录中发现了一个这样的元素。通过CRISPR/Cas9辅助的基因组编辑，我们从胚胎干细胞和胚胎中去除了基因组中的该元件，从这些ES细胞衍生的小鼠表现出Fendrr功能对该元件的部分需求。我们将在体内分析Fendrr中的其他潜在元素。此外，我们将确定Fendrr的全基因组结合位点。Fendrr的人类直系同源物被认为在人类遗传性疾病肺静脉错位的肺泡毛细血管发育不良（ACD/MPV）中发挥作用。患有ACD/MPV的患者表现出许多发育缺陷，如心脏缺陷，但最终死于肺衰竭。我们将使用野生型和Fendrr突变型肺的离体培养来鉴定导致ACD/MPV患者肺衰竭的发育缺陷，并阐明Fendrr在此过程中的分子作用，这里提出的实验旨在拓宽我们对lncRNA Fendrr的体内作用的理解，并揭示lncRNA调控基因组的基本原理。

The most abundant RNA transcripts in the vertebrate transcriptome are long noncoding RNAs (lncRNAs), transcripts that are longer than 200 nucleotides and do not encode proteins. LncRNAs have been associated with epigenetic changes, developmental defects and cancer, and knockouts are sometimes lethal. We showed previously that the lncRNA Fendrr is essential for mouse embryo development and mutant embryos die due to cardiac defects.We will further characterize the molecular roles of Fendrr in the development of the early cardiac cell lineage of the mouse embryo. This work will help us to understand how the loss of Fendrr leads to cardiac defects and how Fendrr, together with the polycomb repressive complex 2 (PRC2), regulates cardiac specific gene expression. Furthermore we will identify additional proteins and protein complexes that interact with Fendrr and will analyze their in vivo role in early cardiac development. In addition, certain elements of the Fendrr transcript can interact directly with the genome to regulate target gene expression and, eventually, aid in recruiting protein complexes to specific sites in the genome. We identified one such element in the Fendrr transcript. By CRISPR/Cas9 aided genome editing we removed this element in the genome from embryonic stem cells and embryos and mice derived from these ES cells exhibit a partial requirement of this element for Fendrr function. We will analyze additional potential elements in Fendrr in vivo. In addition, we will identify genome wide binding sites of Fendrr.The human orthologue of Fendrr is implicated to play a role in the human genetic disorder Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV). Patients with ACD/MPV exhibit numerous developmental defects such as cardiac defects, but ultimately die due to lung failure. We will use lung ex vivo culture of wild type and Fendrr mutant lungs to identify the developmental defects causing the lung failure of ACD/MPV patients and elucidate the molecular role of Fendrr in this process.The experiments proposed here aim to widen our understanding of the in vivo roles of the lncRNA Fendrr and uncover basic principles of genome regulation by lncRNAs in general.