Glial Cell line-derived neurotrophic factor (GDNF) inducible genes regulate neuronal differentiation and kidney development

胶质细胞源性神经营养因子(GDNF)及其家族配体通过激活RET酪氨酸激酶来调节多种神经元的存活和分化。另一方面，GDNF激活RET是发育中的肾脏输尿管芽上皮正常分支所必需的。我们利用mRNA差异显示技术寻找GDNF的即刻-早期反应基因，共分离到14个基因。在这些GDNF诱导基因中，我们发现了一个含有BTB/POZ结构域和10个重复锌指基序的新基因(命名为GZF1)和SEP1基因，该基因编码参与酿酒酵母同源重组过程的DNA链交换蛋白。与其他含有BTB/POZ结构域的蛋白一样，GZF1蛋白具有很强的转录抑制活性。有趣的是，它在小鼠后肾的分支输尿管芽和集合管中检测到高水平的表达，其中RET也表达。GZF1基因的反义硫代寡核苷酸显著损伤后肾器官培养中的输尿管芽分枝，提示GZF1的表达是通过GDNF/RET信号系统诱导的。在SEP1中，我们观察到在GDNF刺激后0.5-2 h和24-48 h，SEP1的诱导出现两个高峰。我们还发现SEP1在小鼠背根神经节和颈上神经节的神经元以及脊髓运动神经元中都有高水平的表达，其中RET也有表达。此外，SEP1还与小鼠脑裂解液中的α-微管蛋白和β-微管蛋白共沉淀。这些结果表明，SEP1是一种GDNF诱导的微管相关蛋白，可能在神经系统中发挥作用。

Glial cell line-derived neurotrophic factor (GDNF) and its family ligands regulate the survival and differentiation of various neurons through activation of RET tyrosine kinase. On the other hand, the activation of RET by GDNF is required for normal branching of the ureteric bud epithelium in the developing kidney. We searched for immediate-early GDNF responsive genes by mRNA differential display technique and have isolated fourteen genes. In these GDNF inducible genes, we identified a novel gene (named GZF1) with a BTB/POZ domain and 10 tandemly repeated zinc finger motifs and the SEP1 gene that encodes a DNA strand exchange protein involved in the homologous recombination process of Saccharomyces cerevisiae. As observed for other proteins with the BTB/POZ domain, the GZF1 protein had strong transcriptional repressive activity. Intriguingly, its expression was detected at high levels in branching ureteric buds and collecting ducts of mouse metanephric kidney in which RET was also expressed. Antisense phosphorothioated oligodeoxynucleotides of the GZF1 gene markedly impaired the ureteric bud branching in the metanephric organ culture, suggesting that the induction of GZF1 expression via the GDNF/RET signaling system is required for renal branching morphogenesis. In the case of SEP1, we observed that SEP1 induction showed two peaks at 0.5-2 h and 24-48 h after GDNF stimulation. We also found that a high level of SEP1 expression in neurons of the dorsal root and superior cervical ganglia and motor neurons of the spinal cord of mice in which RET is also expressed. In addition, SEP1 was co-immunoprecipitated with alpha-and beta-tubulins from the lysate of mouse brain. These results thus suggested that SEP1 is a GDNF-inducible and microtubule-associated protein that may play a role in the nervous system.