Roles of DNA methylation in gastrointestinal smooth muscle cells

描述（由申请人提供）：胃肠道（GI）神经肌肉疾病（运动障碍）以三种关键细胞的功能障碍为特征：Cajal间质细胞（ICC）、肠神经系统（ENS）和平滑肌细胞（SMCs），它们共同控制胃肠道中的SM运动。ENS和ICC分别产生复杂的节律性运动行为和自发的电慢波，两者都控制肌肉收缩和肌肉松弛的最终效应器SMCs。虽然已经有大量的工作研究ENS和ICC功能障碍对GI运动障碍的影响，但SMCs的功能障碍却很少受到关注。SMC功能障碍的知识差距需要解决，因为这三种类型的细胞在物理上是相关的，并且在功能上协同工作：一种细胞类型的功能障碍会影响其他两种细胞。本项目旨在揭示一种分子机制，以了解在胃肠道运动障碍的发展过程中SMCs是如何重塑的。我们最近报道了GI SMCs的发育和存活需要microRNAs (miRNAs)，并且GI SMCs的表型由血清反应因子（SRF）依赖性microRNAs控制。此外，我们的初步研究表明，SMCs的表型变化（肥大）与一组独特的srf依赖性mirna的失调有关，这些mirna受表观遗传DNA甲基化调节。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，在胚胎和出生后的细胞发育过程中显示出SMCs的异常表型。在本项目中，我们提出了三个具体目标：确定srf依赖性mirna在GI SMC发育过程中的作用，确定DNA甲基化在GI SMC发育过程中的作用，以及发现DNA甲基转移酶（Dnmt1）靶向mirna调节GI SMC肥大的作用。该项目的具体目标的完成将为理解srf依赖性miRNA基因在胃肠道神经肌肉疾病的SMCs中如何进行表观遗传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厚相关疾病的诊断工具，而且还有助于找到治疗靶点，从而有可能逆转导致这些病理状况的表观遗传变化，从而可能逆转这些疾病中发生的一些不想要的病理变化。

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.