Regulation of differentiation in esophageal epithelia

描述(申请人提供)：KLF4(Kruppel-like factor4，以前称为GKLF)是一种上皮性锌指蛋白，控制皮肤和胃肠道的细胞增殖和分化。在生长受阻的细胞中发现高水平的KLF4 mRNA，在分裂细胞中几乎检测不到KLF4。KLF4通常只在分化的上皮细胞区域发现，包括在食道，在上皮不典型增生中表达下调，包括息肉和癌症。KLF4零突变纯合子小鼠在出生后第1天死亡，并显示出皮肤和结肠的异常分化(Katz等人，Development，2002)。利用小鼠的组织特异性基因去除，我们还证明了KLF4在成人胃上皮细胞的增殖和分化中起着至关重要的作用(Katz等人，胃肠病学，2005年)。由于KLF4调控着许多已知在食道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，KLF4无疑也在食道中起着关键作用。值得注意的是，角蛋白19参与了食道和胰腺的恶性转化。然而，KLF4在食道上皮细胞中的功能尚未被研究。在这些研究中，我们将通过检验以下假设来检验KLF4在食道中的作用：(1)KLF4在食道上皮细胞中的缺失导致细胞增殖增加和/或分化改变，(2)KLF4在食道上皮细胞中过表达改变细胞分化和/或增殖。以下相关的特定目标将使用遗传和生化方法检验这些假说：(1)分析KLF4在食道上皮细胞动态平衡中的作用(A)通过研究KLF4在食道粘膜中缺失的成年小鼠的组织学、细胞增殖和分化，以及(B)分析KLF4在原代食道细胞中缺失的影响；以及(2)通过(A)利用食道特异的EBV ED-L2启动子在小鼠体内过表达KLF4，以及(B)通过分析KLF4在原代食道细胞中表达上调的影响，来研究KLF4在食道上皮细胞中过表达的影响。综上所述，这些以机制为导向的互补性研究将为正常的食道上皮细胞动态平衡提供新的见解，并为在粘膜损伤和转化过程中如何颠覆增殖-分化平衡建立范例。

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.