Regulation of differentiation in esophageal epithelia

描述（由申请人提供）：Klf4 （kruppel样因子4，以前称为GKLF）是一种上皮锌指蛋白，控制皮肤和胃肠道的细胞增殖和分化。Klf4 mRNA在生长停滞的细胞中含量很高，在分裂细胞中几乎检测不到。Klf4通常只存在于分化的上皮细胞区域，包括食道，在包括息肉和癌症在内的上皮发育不良中表达下调。Klf4零突变纯合的小鼠在出生后1天死亡，并表现出皮肤和结肠的异常分化（Katz et al, Development, 2002）。通过对小鼠进行组织特异性基因消融，我们也证明了Klf4在成人胃上皮细胞增殖和分化中起着至关重要的作用（Katz et al, Gastroenterology, 2005）。由于Klf4调节了许多已知在食管增殖和分化中起重要作用的基因，包括角蛋白4、ED-L2和角蛋白19，因此Klf4无疑在食管中也起着关键作用。值得注意的是，角蛋白19参与食道和胰腺的恶性转化。然而，Klf4在食管上皮细胞中的功能尚未被研究。在这些研究中，我们将通过验证以下假设来检验Klf4在食管中的作用：(1)食管上皮中Klf4的缺失导致细胞增殖和/或分化改变，(2)食管上皮细胞中Klf4过表达改变细胞分化和/或增殖。以下相关的特异性目的将通过遗传学和生化方法来验证这些假设：(1)分析Klf4在食管上皮稳态中的功能(a)通过研究食管黏膜中缺乏Klf4的成年小鼠的组织学、细胞增殖和分化，(b)通过分析Klf4缺失对原代食管细胞的影响；(2)通过(a)使用食管特异性EBV ED-L2启动子在小鼠中过表达Klf4， (b)分析Klf4在原代食管细胞中表达增加的影响，研究Klf4在食管上皮中过表达的影响。综上所述，这些以机制为导向和互补的研究将为正常食管上皮稳态提供新的见解，并为粘膜损伤和转化过程中增殖分化平衡如何被破坏建立范式。

DESCRIPTION (provided by applicant): Klf4 (Kruppel-like factor 4, previously known as GKLF) is an epithelial zinc-finger protein which controls cellular proliferation and differentiation in the skin and gastrointestinal tract. Klf4 mRNA is found at high levels in growth-arrested cells and is nearly undetectable in dividing cells. Klf4 is normally found only in regions of differentiating epithelial cells, including in the esophagus, and expression is downregulated in epithelial dysplasia, including polyps and cancer. Mice homozygous for a null mutation in Klf4 die on postnatal day 1 and show abnormal differentiation of the skin and colon (Katz et al, Development, 2002). Using tissue-specific gene ablation in mice, we have also demonstrated that Klf4 plays a vital role in adult gastric epithelial proliferation and differentiation (Katz et al, Gastroenterology, 2005). As Klf4 regulates a number of genes known to be important in esophageal proliferation and differentiation, including keratin 4, ED-L2, and keratin 19, Klf4 undoubtedly plays a critical role in the esophagus as well. Notably, keratin 19 is involved in malignant transformation in both the esophagus and pancreas. Nonetheless, the function of Klf4 in esophageal epithelial cells has not been investigated. In these studies, we will examine the role of Klf4 in the esophagus by testing the following hypotheses: (1) Loss of Klf4 in esophageal epithelia results in increased cell proliferation and/or altered differentiation, and (2) Klf4 overexpression in esophageal epithelial cells alters cellular differentiation and/or proliferation. The following interrelated Specific Aims will test these hypotheses using genetic and biochemical approaches: (1) To analyze the function of Klf4 in esophageal epithelial homeostasis (a) through studies of histology, cell proliferation, and differentiation in adult mice lacking Klf4 in the esophageal mucosa and (b) by analyzing the effects of Klf4 deletion in primary esophageal cells; and (2) To study the effect of Klf4 overexpression in esophageal epithelia by (a) overexpressing Klf4 in mice using the esophageal-specific EBV ED-L2 promoter and (b) by analyzing the effects of increased Klf4 expression in primary esophageal cells. Taken together, these mechanistically oriented and complementary studies will provide new insights into normal esophageal epithelial homeostasis and establish paradigms for how the proliferation-differentiation equilibrium may be subverted during mucosal injury and transformation.