Mechanism Of Action And Functions Of The Gli-related Proteins Glis 1-3

GLIS1-3是本实验室发现的新基因。GLIS1-3基因编码Kruppel样锌指蛋白，含有5个串联的锌指基序，与Kruppel样锌指蛋白Gli和Zic亚家族成员的同源性最高。此外，GLIS1和GLIS3的锌指结构域与果蝇Gleful/Lame鸭锌指结构域有很高的同源性，提示它可能是果蝇GLIS1和-3的同源物。GLIS3：GLIS3在胰腺发育中起关键作用，并与新生儿糖尿病和甲状腺功能减退(NDH)综合征有关。GLIS3在胰岛β细胞中高表达，通过与胰岛β细胞启动子区域的谷氨酸结合位点，调节包括胰岛素基因在内的多种胰岛细胞基因的转录。此外，GLIS3还调节胰腺PP细胞中胰多肽的表达。GLIS3与其他β细胞转录因子协同调节这些基因的转录。在胰腺发育过程中，GLIS3早在具有双潜能的胰腺祖细胞中表达，并在胰管和内分泌祖细胞中持续表达。当内分泌祖细胞分化为不同的内分泌谱系时，GLIS3在β细胞和PP细胞中保持表达，但在胰高血糖素、生长抑素和Ghrelin产生细胞中被抑制。由于胰岛素基因表达减少和胰岛β细胞数量减少，GLIS3缺乏会导致新生儿糖尿病的发生。GLIS3通过募集CBP/p300在胰岛素在胰岛β细胞中的转录调控中发挥关键作用，CBP/p300可能作为一个支架，在胰岛素启动子上形成包含Pdx1、NeuroD1和Mafa的更大的转录调控复合体。GLIS3功能障碍也可导致囊性肾病的发生，提示GLIS3在维持正常肾功能中起着关键作用。酵母双杂交分析和质谱仪鉴定了几种与GLIS3相互作用的蛋白质，包括几种Hect-泛素连接酶。这些连接酶促进GLIS3泛素化，从而降低GLIS3蛋白的稳定性和GLIS3介导的转录激活。GLIS3在肾脏的小管和集合管也有表达，GLIS3的缺失会导致多囊肾病。此外，GLIS3在精子发生中起着关键作用。它在精原干细胞中表达，当这些细胞分化为分化的精原细胞时，它的表达下调。缺乏GLIS3的小鼠缺乏成熟的精子，因此不育。GLIS1-3在发育过程中以时间和空间的方式表达。GLIS3在甲状腺激素的合成中也是至关重要的，因为GLIS3缺乏会导致甲状腺功能减退，这是因为甲状腺激素的产生大大减少。GLIS3是甲状腺激素生物合成和甲状腺滤泡细胞增殖所必需的。与野生型小鼠相比，在缺碘条件下，GLIS3基因敲除小鼠不会出现甲状腺肿大。这些研究表明，GLIS3在几个组织中具有关键功能，并在许多主要病理过程中发挥关键作用。 Glis2在肾脏中高表达。为了深入了解Glis2的生理功能，我们培育了Glis2基因缺陷的小鼠。Glis2基因缺陷的小鼠会发展成一种慢性肾脏疾病，即肾小球肾炎，并伴有肾脏萎缩、纤维化和炎症。最终，Glis2缺陷小鼠会因肾功能衰竭而过早死亡。在Glis2缺陷小鼠的肾脏中诱导了大量参与免疫反应/炎症和纤维化/组织重塑的基因。会导致肾功能衰竭。我们的研究表明，Glis2在调节肾脏炎症和维持正常肾功能中起着关键作用。Glis2抑制几种炎症基因的转录。 GLIS1基因敲除小鼠发生突眼，这与青光眼特征的眼压升高有关。眼压的升高与小梁网的退化有关，小梁网是前房排出液体的重要组织。

Glis1-3 are novel genes identified in our laboratory. The Glis1-3 genes encode Kruppel-like zinc finger proteins containing five tandem zinc finger motifs that exhibit highest homology with those of members of the Gli and Zic subfamilies of Kruppel-like zinc finger proteins. In addition, the zinc finger domain of Glis1 and -3 exhibit high homology with that of Drosophila gleeful/lame duck suggesting that it may be the Drosophila homologue of Glis1 and -3. Glis3: Glis3 plays a critical role in pancreatic development and has been implicated in a syndrome with neonatal diabetes and hypothyroidism (NDH). Glis3 is highly expressed in pancreatic beta cells where it regulates the transcription of several beta cell genes, including the insulin gene, by binding to Glis-binding sites in their promoter region. In addition, Glis3 regulates pancreatic polypeptide expression in pancreatic PP cells. Glis3 regulates the transcription of these genes in coordination with other beta cell transcription factors. During pancreatic development Glis3 is expressed as early as in the bipotent pancreatic progenitors and remains expressed in pancreatic ducts and endocrine progenitors. When endocrine progenitors differentiate into the different endocrine lineages, Glis3 remains expressed in the beta and PP cells, but is repressed in glucagon, somatostatin and ghrelin producing cells. Glis3 deficiency leads to the development of neonatal diabetes, due to reduced insulin gene expression and in the number of pancreatic beta cells. Glis3 plays a critical role in the transcriptional regulation of insulin in pancreatic beta cells by recruiting CBP/p300, which may serve as a scaffold for the formation of a larger transcriptional regulatory complex containing Pdx1, NeuroD1, and MafA at the insulin promoter. Dysfunction of Glis3 also leads to development of cystic renal disease suggesting that Glis3 plays a critical role in maintaining normal renal functions. Yeast two-hybrid analysis and mass spectrometry identified several Glis3-interacting proteins, including several HECT-ubiquitin ligases. These ligases promote Glis3 ubiquitination thereby reducing the stability of Glis3 protein and Glis3-mediated transcriptional activation. Glis3 is also expressed in the tubules and collecting ducts of the kidney and loss of Glis3 leads to polycystic kidney disease. In addition, Glis3 plays a critical role in spermatogenesis. It is expressed in spermatogonial stem cells and becomes down-regulated when these cells differentiate into differentiated spermatogonia. Mice deficient in Glis3 are deficient in mature spermatozoa and therefore infertile. Glis1-3 are expressed in a temporal and spatial manner during development. Glis3 is also critical in the synthesis of thyroid hormone in that Glis3 deficiency results in hypothyroidism due to a greatly reduced thyroid hormone production. Glis3 is essential for thyroid hormone biosynthesis and thyroid follicular cell proliferation. Under iodide-deficiency conditions Glis3 knockout mice do not develop goiter in contrast to wild type mice. These studies have demonstrated that Glis3 has a critical function in several tissues and plays a critical role in a number of major pathologies. Glis2 is highly expressed in kidney. To obtain insight into the physiological functions of Glis2, mice deficient in Glis2 were generated. Glis2 deficient mice develop a chronic kidney disease, nephronophthisis, that is accompanied by renal atrophy, fibrosis and inflammation. Ultimately Glis2 deficient mice die prematurely of renal failure. A large number of genes involved in immune responses/inflammation and fibrosis/tissue remodeling are induced in kidneys of Glis2 deficient mice. results in renal failure. Our study indicates that Glis2 plays a critical role in the regulation of renal inflammation and the maintenance of normal kidney functions. Glis2 represses the transcription of several inflammatory genes. Glis1 knockout mice develop proptosis that is related to increased intraocular pressure (IOP) characteristic of glaucoma. The increase in IOP is related to degeneration of the trabecular meshwork, a tissue that is important in draining fluid from the anterior chamber.