COREGULATORY MODEL OF SMOOTH MUSCLE MYOGENESIS

成熟的胃肠道(GI)平滑肌细胞(SMCs)具有高度的发育可塑性，能够在增殖状态和分化状态之间相互转换以响应外界刺激。胃肠道SMC分化异常与多种胃肠道疾病相关，包括先天性巨结肠、克罗恩病、溃疡性结肠炎、动力障碍和胃肠道平滑肌肿瘤。这一建议的目的是为了更好地了解控制胃肠道平滑肌发育的分子机制。我们的假设是，胃肠道平滑肌的肌肉发生是由转录因子的协同表达控制的，这些转录因子是所有肌肉谱系共同的，也是那些平滑肌特有的。这一假说得到了我们实验室最近的数据的支持，这些数据证实了伽马-平滑肌异肌动蛋白基因启动子中的一个关键调控复合体。增殖和分化的GI SMC表型之间的相互转换涉及血清反应因子(SRF)、MEF2的不同同型以及其他未知转录因子与这一关键调控复合体的不同结合。在G1期的平滑肌肿瘤和溃疡性结肠炎中，该复合体对这些转录因子的利用发生了改变，提示SRF和MEF2可能在胃肠道平滑肌的发病机制中起作用。我们计划通过阐明在原代培养的胃肠道平滑肌细胞中控制γ-平滑肌异肌动蛋白基因表达的因素，来确定参与胃肠道平滑肌细胞发生的关键转录因子。我们将使用一种独特的大规模筛选技术来分离和鉴定新的胃肠道平滑肌特异性转录因子。培养的GI SMC将被用于评估SRF、MEF2和新的转录因子在调节GI SMC分化中所起的功能作用。识别参与胃肠道平滑肌细胞发生的关键转录因子，并确定它们如何相互作用来调节胃肠道SMC表型，对于更好地了解各种胃肠道疾病中胃肠道平滑肌细胞的发病机制至关重要。

Mature gastrointestinal (GI) smooth muscle cells (SMCs) possess a high degree of developmental plasticity retaining the ability to interconvert between proliferative and differentiated states in response to external stimuli. Dysregulation of GI SMC differentiation is associated with a variety of GI disorders including Hirschsprung's disease, Crohn's disease, ulcerative colitis, motility disorders, and GI smooth muscle tumors. The goal of this proposal is to gain a better understanding of the molecular mechanisms controlling GI smooth muscle development. Our hypothesis is that GI smooth muscle myogenesis is controlled by the synergistic expression of transcription factors that are common to all muscle lineages, as well as those that are smooth muscle specific. This hypothesis is supported by recent data from our lab identifying a key regulatory complex within the gamma-smooth muscle isoactin gene promoter. Interconversion between proliferative and differentiated GI SMC phenotypes involves differential binding of serum response factor (SRF), distinct isotypes of MEF2, and additional unidentified transcription factors to this critical regulatory complex. Utilization of these same transcription factors by this complex is altered in G1 smooth muscle tumors and ulcerative colitis suggesting that SRF and MEF2 may play a role in GI smooth muscle pathogenesis. We plan to identify the key transcription factors involved in GI smooth muscle myogenesis by elucidating the factors controlling gamma-smooth muscle isoactin gene expression in primary cultures of GI SMCs. We will use a unique, mass-arrayed screening technique to isolate and identify novel GI smooth muscle-specific transcription factors. Cultured GI SMCs will be used to assess the functional role that SRF, MEF2, and novel transcription factors play in modulating GI SMC differentiation. Identifying the key transcription factors involved in GI smooth muscle myogenesis, and determining how they interact to modulate GI SMC phenotype is critical to gaining a better understanding of GI smooth muscle pathogenesis in a variety of GI diseases.