Regulation of differentiation in esophageal epithelia

描述（由申请人提供）：Klf 4（Kruppel样因子4，以前称为GKLF）是一种上皮锌指蛋白，控制皮肤和胃肠道中的细胞增殖和分化。Klf 4 mRNA在生长停滞细胞中以高水平存在，在分裂细胞中几乎检测不到。Klf 4通常仅在分化上皮细胞的区域中发现，包括在食管中，并且在上皮发育不良（包括息肉和癌症）中表达下调。Klf 4无效突变纯合的小鼠在出生后第1天死亡，并显示皮肤和结肠的异常分化（Katz等人，Development，2002）。在小鼠中使用组织特异性基因消融，我们还证明Klf 4在成人胃上皮增殖和分化中起重要作用（Katz等人，Gastroenterology，2005）。由于Klf 4调节许多已知在食管增殖和分化中重要的基因，包括角蛋白4、ED-L2和角蛋白19，Klf 4无疑在食管中也起着关键作用。值得注意的是，角蛋白19参与食管和胰腺的恶性转化。然而，Klf 4在食管上皮细胞中的功能尚未研究。在这些研究中，我们将通过测试以下假设来检查Klf 4在食管中的作用：（1）食管上皮中Klf 4的缺失导致细胞增殖增加和/或分化改变，和（2）食管上皮细胞中Klf 4过表达改变细胞分化和/或增殖。以下相关的具体目的将使用遗传学和生物化学方法来检验这些假设：（1）通过研究食管粘膜中Klf 4缺失的成年小鼠的组织学、细胞增殖和分化以及（B）通过分析原代食管细胞中Klf 4缺失的影响来分析Klf 4在食管上皮稳态中的功能;和（2）通过（a）使用食管特异性EBV ED-L2启动子在小鼠中过表达Klf 4和（B）通过分析原代食管细胞中Klf 4表达增加的效果来研究Klf 4在食管上皮中过表达的效果。总而言之，这些以机制为导向的互补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期间如何破坏增殖-分化平衡建立范式。

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.