Regulation of differentiation in esophageal epithelia

Klf 4（KruppeMike因子4，以前称为GKLF）是一种上皮锌指蛋白，其控制 皮肤和胃肠道中的细胞增殖和分化。Klf 4 mRNA在高水平 在生长停滞的细胞中水平，在分裂的细胞中几乎检测不到。Klf 4通常只存在于 分化上皮细胞的区域，包括在食管中，并且表达在 上皮发育不良，包括息肉和癌症。Klf 4无效突变纯合子小鼠死亡 出生后第1天，显示皮肤和结肠的异常分化（Katz等，Development，2002）。 在小鼠中使用组织特异性基因切除，我们还证明Klf 4在成年小鼠中起着至关重要的作用。 胃上皮细胞增殖和分化（Katz等，Gastroenterology，2005）。由于Klf 4调节了 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是 在食道和胰腺都发生了恶性转化。尽管如此，Klf 4的功能 在食管上皮细胞中的作用尚未研究。在这些研究中，我们将研究Klf 4在以下方面的作用： 食管通过测试以下假设：（1）K！食管上皮中的f4导致 增加的细胞增殖和/或改变的分化，和（2）Klf 4在食管上皮中过表达 细胞改变细胞分化和/或增殖。以下相互关联的具体目标将测试 利用遗传学和生物化学的方法研究这些假说：（1）分析Klf 4在 食管上皮内环境稳定（a）通过研究组织学、细胞增殖和分化， （B）通过分析原发性食管癌中Klf 4缺失的影响， 食管上皮细胞;和（2）通过（a）研究Klf 4过表达在食管上皮中的作用， 使用脑血管特异性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表达增加的影响。综合来看，这些机制 定向和补充研究将为正常食管上皮稳态提供新的见解 并建立了如何在增殖分化平衡可能被颠覆的范式， 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.