Roles of DNA methylation in gastrointestinal smooth muscle cells

描述（由申请人提供）：胃肠（GI）神经肌肉疾病（运动性疾病）的特征在于三种类型的关键细胞功能障碍：Cajal间质性神经元（ICC）、肠神经系统（ENS）和平滑肌细胞（SMC），它们共同控制胃肠道中的SM运动性。ENS和ICC分别产生复杂的节律性运动行为和自发电慢波，它们都控制SMC，SMC是肌肉收缩和肌肉松弛的最终效应器。虽然已经有大量的工作调查ENS和ICC功能障碍在GI动力障碍中的作用，但SMCs的功能障碍受到的关注要少得多。SMC功能障碍知识的差距需要解决，因为这三种类型的细胞在物理上是相关的，并在功能上一起工作：一种细胞类型的功能障碍可以影响其他两种。本项目旨在揭示一个分子机制，了解如何平滑肌细胞在胃肠道动力障碍的发展过程中重塑。我们最近报道，胃肠道平滑肌细胞需要microRNA（miRNAs）的发展和动物的生存，而胃肠道平滑肌细胞的表型是由血清反应因子（SRF）依赖的microRNA控制。此外，我们的初步研究表明，SMC的表型变化（肥大）与一组独特的SRF依赖性miRNAs的失调有关，这些miRNAs受表观遗传DNA甲基化的调节。为了研究这一新的分子机制，我们建立了6个转基因动物模型，这些模型在胚胎和出生后细胞发育过程中显示出SMC的异常表型。在这个项目中，我们提出了三个具体的目标：定义在胃肠道平滑肌细胞的发展过程中的SRF依赖的miRNA的作用，定义在胃肠道平滑肌细胞的发展过程中的DNA甲基化的作用，并发现DNA甲基转移酶（Dnmt 1）靶向的调控胃肠道平滑肌细胞肥大的miRNA的作用。该项目具体目标的完成将为理解SRF依赖性miRNA基因如何在GI神经肌肉疾病的SMC中表观遗传学重编程提供令人兴奋的新机制。识别表观遗传变化不仅有助于开发肥大相关疾病的诊断工具，而且有助于开发一种治疗靶点，该靶点有可能逆转导致这些病理状况的表观遗传变化，从而可能逆转一些不需要的表观遗传变化。这些疾病中发生的病理变化。

DESCRIPTION (provided by applicant): Gastrointestinal (GI) neuromuscular disorders (motility disorders) are characterized by dysfunctions of three types of key cells: interstitial cels of Cajal (ICC), enteric nervous system (ENS), and smooth muscle cells (SMCs), which cooperatively control SM motility in the GI tract. ENS and ICC generate complex rhythmic motor behavior and spontaneous electrical slow waves, respectively, both of which control SMCs, the final effectors for muscle contraction and muscle relaxation. Although there has been a significant amount of work investigating the effects of ENS and ICC dysfunction in GI motility disorders, the dysfunction of SMCs has received much less attention. The gap in the knowledge of SMC dysfunction needs to be addressed, since the three types of cells are physically associated and functionally working together: dysfunction of one cell type can affect the other two. This present project seeks to uncover a molecular mechanism for understanding how SMCs are remodeled during the development of GI motility disorders. We have recently reported that GI SMCs require microRNAs (miRNAs) for the development and survival of animals, and that the phenotypes of GI SMCs are controlled by serum response factor (SRF)-dependent microRNAs. In addition, our preliminary study suggested that the phenotypic change (hypertrophy) of SMCs is linked to dysregulation of a unique set of SRF-dependent miRNAs which are regulated by epigenetic DNA methylation. To study this new molecular mechanism, we generated six transgenic animal models that display abnormal phenotypes of SMCs during the embryonic and post-natal development of the cells. In this project, we propose three specific aims: define the roles of SRF-dependent miRNAs during the development of GI SMCs, define the roles of DNA methylation during the development of GI SMCs, and discover the roles of DNA methyltransfertase (Dnmt1)-targeting miRNAs that regulate GI SMC hypertrophy. Completion of the specific aims of this project will provide an exciting new mechanism for understanding how the SRF-dependent miRNA genes are epigenetically reprogrammed in the SMCs of GI neuromuscular disorders. Identifying the epigenetic changes will aid not only in the development of a diagnostic tool for hypertrophy-related diseases, but also of a therapeutic target that has the potential to reverse the epigenetic changes that are responsible for these pathological conditions, and thus possibly reverse some of the unwanted pathological changes that occur in these disorders.