DACH1 transcriptomic regulation of glucocorticoid-responsive glomerular disease

项目总结： 足细胞损伤是包括微小病变在内的所有蛋白尿肾脏疾病的致病事件。 (MCD)和FSGS。糖皮质激素(GC)通常是这些疾病的初始和首选治疗方法。这个 GCs的有益作用不是由免疫调节引起的，而是通过它们对 足细胞。不幸的是，GC疗法充满了严重的全身毒性，限制了它们的使用。鉴定 足细胞中基本有益的GC诱导靶点的发现可能会带来新的治疗方法， 将毒性降至最低，但保持疗效。在目前的提案中，我们发现减少了对 大规模突变筛选中的转录因子dachshund1(DACH1)，旨在识别 恢复了对遗传耐伤害足细胞的伤害易感性。我们发现DACH1对于 足细胞在新的全局和特定足细胞敲除小鼠模型中的作用。重要的是，足细胞- 特定的DACH1杂合子小鼠，其肾小球DACH1表达水平降低，类似于 人类MCD和FSGS患者对阿霉素肾病非常敏感，并且这种表型 经GC治疗后均有改善。我们发现，GC给药导致早期和显著的诱导 DACH1的表达，并通过芯片实验证实GC受体与DACH1启动子的结合。此外， DACH1内含子SNP(Rs626277)的保护性等位基因已在全基因组中被鉴定 与事件和流行的CKD有关的关联研究，引入了GC-α转录因子结合 在存在风险等位基因的情况下被取消的位置。当我们在记者研究中测试这些等位基因时， 保护等位基因显著增强DACH1启动子活性对GC的响应，与GC- 增强增强剂功能。在GC治疗的肾移植患者中，保护性的rs626277等位基因 与肾小球DACH1表达增加及蛋白尿改善密切相关。此外， 在一组MCD和FSGS患者中，保护性和危险等位基因与GC反应性和 分别为抗性。我们假设DACH1是有益的中枢转录调节因子 肾小球GC反应和调节足细胞DACH1转录rs626277基因状态 在糖皮质激素治疗环境中，是肾病综合征糖皮质激素反应性的重要决定因素 病人。我们的建议包括三个具体目标：i)证明DACH1的过度表达具有保护性 使用一种新的可诱导足细胞特异的DACH1转基因小鼠模型II)表明 使用新的可诱导足细胞特异性表达在缺乏DACH1表达的情况下减轻足细胞的GCS 基因敲除小鼠III)在GC治疗的MCD和FSGS中，rs626277基因状态与临床结果相关 海王星的患者和交叉检查从前两个目标获得的机制和转录数据 在这些病人身上。如果得到证实，rs626277基因状态可用于个体化风险-收益分层 肾病综合征患者在开始治疗前进行GC治疗。

Project Summary: Podocyte injury is the causative event in all proteinuric kidney diseases including minimal change disease (MCD) and FSGS. Glucocorticoids (GCs) are often the initial and preferred treatment for these conditions. The beneficial effects of GCs are not caused by immunomodulation, but are mediated by their direct effects on podocytes. Unfortunately, GC therapy is riddled with severe systemic toxicities that limit their use. Identification of essential salutary GC-induced targets in podocytes might allow for new therapeutic approaches that can minimize toxicity but maintain efficacy. In the current proposal, we identified diminished expression of the transcription factor dachshund1 (DACH1) in a large-scale mutagenic screen designed to identify mutations that restored injury susceptibility to genetically injury-resistant podocytes. We found DACH1 to be essential to podocyte function in both novel global and podocyte-specific knock out mouse models. Importantly, podocyte- specific DACH1 heterozygous mice, which have reduced glomerular DACH1 expression levels similar to human MCD and FSGS patients, were remarkably susceptible to adriamycin nephropathy, and this phenotype was ameliorated by GC therapy. We found that GC administration caused early and significant induction of DACH1 expression, and we confirm binding of GC receptor to the DACH1 promoter by ChIP assay. Moreover, the protective allele of a DACH1 intronic SNP (rs626277), which has been identified in genome-wide association studies as linked to incident and prevalent CKD, introduced a GC-alpha transcription factor-binding site that was abrogated in the presence of the risk allele. When we tested these alleles in reporter studies, the protective allele dramatically augmented DACH1 promoter activity in response to GCs, consistent with GC- potentiated enhancer function. In GC treated kidney transplant patients, the protective rs626277 allele correlated closely with increased glomerular DACH1 expression and improvement in proteinuria. Furthermore, in a cohort of MCD and FSGS patients, protective and risk alleles correlated with GC responsiveness and resistance respectively. We hypothesize that DACH1 is a central transcriptomic regulator of the salutary glomerular GC response and that rs626277 genotype status, which modulates podocyte DACH1 transcription in the setting of GC therapy, is an important determinant of GC-responsiveness in nephrotic syndrome patients. Our proposal includes three specific aims: i) demonstrate that DACH1 over-expression is protective using a novel inducible podocyte-specific DACH1 transgenic mouse model ii) show that the beneficial effects of GCs in podocytes are mitigated in the absence of DACH1 expression using novel inducible podocyte-specific knockout mice iii) correlate rs626277 genotype status with clinical outcomes in GC-treated MCD and FSGS patients in NEPTUNE and cross-examine mechanistic and transcriptomic data obtained from the first two aims in these patients. If validated, rs626277 genotype status could serve to individualize risk-benefit stratification of GC therapy in nephrotic syndrome patients PRIOR to treatment initiation.