Expression profiling of Get1 -/- bladder

Skin and bladder epithelia form effective permeability barriers through the activation of distinct differentiation gene programs. Employing a genome-wide gene expression study, we identified transcription regulators whose expression correlates highly with that of differentiation markers both in bladder and skin, including the Grainyhead factor Get1/Grhl3, already known to be important for epidermal barrier formation. In the bladder, Get1 is most highly expressed in the differentiated umbrella cells and its mutation in mice leads to a defective bladder epithelial barrier formation due to failure of apical membrane specialization. Genes encoding components of the specialized urothelial membrane, the uroplakins, were downregulated in Get1-/- mice. At least one of these genes, Uroplakin II, is a direct target of Get1. The urothelial-specific activation of the Uroplakin II gene is due to selective binding of Get1 to the Uroplakin II promoter in urothelial cells, most likely regulated by histone modifications. These results demonstrate a key role for Get1 in urothelial differentiation and barrier formation. To gain insights into molecular mechanisms of bladder defects in Get1-/- mice, we profiled bladders of three Get1-/- and three Get +/- E18.5 mice.皮肤与膀胱上皮通过激活不同的分化基因程序，构建起高效的通透性屏障。本研究借助全基因组基因表达分析，鉴定出一批转录调控因子，其表达水平与膀胱及皮肤中的分化标志物高度相关，其中包括Grainyhead因子Get1/Grhl3——该因子已被证实对表皮屏障形成具有关键作用。在膀胱组织中，Get1在分化成熟的伞状细胞内表达量最高；小鼠体内Get1突变会因顶端膜特化失败，引发膀胱上皮屏障形成缺陷。编码特化尿路上皮膜结构组分的基因——尿斑蛋白（uroplakins）家族基因——在Get1基因敲除（Get1-/-）小鼠体内呈现表达下调。上述家族基因中至少有一个——尿斑蛋白II（Uroplakin II）——是Get1的直接靶标。尿斑蛋白II基因的尿路上皮特异性激活，源于Get1在尿路上皮细胞中选择性结合该基因的启动子区域，这一调控过程大概率依赖组蛋白修饰。上述研究结果证实，Get1在尿路上皮分化及屏障形成过程中发挥关键作用。为深入解析Get1基因敲除（Get1-/-）小鼠膀胱缺陷的分子机制，我们对3只Get1-/-小鼠与3只杂合型（Get+/-）E18.5胎龄小鼠的膀胱组织开展了表达谱分析。