Regulation of differentiation in esophageal epithelia

KLF4(KruppeMike factor4，以前称为GKLF)是一种上皮性锌指蛋白，它控制 皮肤和胃肠道中的细胞增殖和分化。KLF4基因表达水平较高 在生长受阻的细胞中几乎检测不到，在分裂细胞中几乎检测不到。KLF4通常只在 分化上皮细胞的区域，包括在食道中，并且表达下调 上皮异型增生，包括息肉和癌症。KLF4基因零突变纯合子小鼠死亡 出生后第1天，表现为皮肤和结肠的异常分化(Katz等，Development，2002)。 利用小鼠的组织特异性基因消融，我们还证明了KLF4在成人中起着至关重要的作用 胃上皮细胞的增殖和分化(Katz等人，胃肠病学，2005年)。因为KLF4调节了一个 一些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是 在食道和胰腺都发生了恶变。尽管如此，KLF4的功能 在食道上皮细胞中的作用尚未被研究过。在这些研究中，我们将研究KLF4在 通过检验以下假设：(1)食道上皮中K！F4的丢失导致 促进细胞增殖和/或改变分化，以及(2)KLF4在食道上皮中过表达 细胞改变细胞分化和/或增殖。以下相互关联的具体目标将受到考验 这些假说使用遗传和生化方法：(1)分析KLF4在 食道上皮细胞动态平衡(A)通过组织学、细胞增殖和分化研究 成年小鼠在食道粘膜中缺乏KLF4和(B)通过分析KLF4缺失对原代小鼠的影响 (2)通过(A)研究KLF4在食道上皮细胞中过表达的作用。 利用食道特异性EB病毒ED-L2启动子在小鼠中过表达KLF4 原代培养的食道细胞中KLF4表达增加的影响。总而言之，这些机械地 定向性和互补性研究将为正常的食道上皮稳态提供新的见解 并建立了如何颠覆增殖-分化平衡的范例 粘膜损伤和转化。

Klf4 (KruppeMike 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 evels 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 nvolved 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 K!f4 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.