Self-defense of the kidney: Probing monoallelic expression and functional effects of proteinuria-associated CUBN variants

肾脏的自卫：探讨蛋白尿相关 CUBN 变异的单等位基因表达和功能影响

• 批准号: 426446721
• 负责人: Professor Dr. Matias Simons
• 金额: --
• 依托单位: Institut für Humangenetik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/426446721?language=en
• 关键词: Self; defense; kidney; Probing; monoallelic

The benefits of diploidy are considered to involve masking partially recessive mutations and to increase genetic diversity, which in turn may promote stress resilience and cellular plasticity. Glomerular injury, such as in nephrotic syndrome and diabetic nephropathy, can lead to tubulointerstitial fibrosis, a major driver of disease progression. Key cell types in this context are proximal tubular cells (PTCs), because they have a high metabolic demand and are continuously overloaded by the reabsorption of the proteins and lipids passing the leaky glomerulus. Particularly, saturated fatty acids carried by albumin are metabolized by the PTCs but can also cause ER stress and cell damage upon uptake. Here, I hypothesize that the combination of high functional genetic diversity and monoallelic expression at the CUBN locus, encoding for the uptake receptor cubilin, is an ancient mechanism for the protection against kidney disease. This hypothesis is based on our recent finding that CUBN mutations are very well tolerated by humans and may even confer selective heterozygote advantages in evolution despite causing urinary protein loss (or proteinuria). To address this hypothesis, we will first explore whether monoallelic CUBN expression generates beneficial cell competition among PTCs under different stress conditions. For this, we will use heterozygous CUBN-GFP cell culture and mice, in which monoallelic expression previously could be generated. Second, we will functionally validate the identified CUBN variants in the mouse and test their potency in protecting against glomerular proteinuria. Altogether, we aim to establish a novel paradigm for kidney protection with high relevance for the diagnosis, prognosis and treatment of proteinuric kidney disease.

二倍体的好处被认为涉及掩盖部分隐性突变并增加遗传多样性，这反过来又可能促进应激恢复力和细胞可塑性。肾小球损伤，如肾病综合征和糖尿病肾病，可导致肾小管间质纤维化，这是疾病进展的主要驱动因素。在这种情况下，关键的细胞类型是近端小管细胞（PTC），因为它们具有高代谢需求，并且通过蛋白质和脂质的重吸收而持续超载通过渗漏的肾小球。特别地，由白蛋白携带的饱和脂肪酸被PTC代谢，但也可以在摄取时引起ER应激和细胞损伤。在这里，我假设在CUBN基因座的高功能遗传多样性和单等位基因表达的组合，编码摄取受体cubilin，是一个古老的机制，保护肾脏疾病。这一假设是基于我们最近的发现，即CUBN突变对人类的耐受性非常好，甚至可能在进化中赋予选择性杂合子优势，尽管会导致尿蛋白丢失（或蛋白尿）。为了解决这一假设，我们将首先探索在不同的应激条件下，单等位基因CUBN表达是否在PTC之间产生有益的细胞竞争。为此，我们将使用杂合CUBN-GFP细胞培养物和小鼠，其中先前可以产生单等位基因表达。其次，我们将在小鼠中功能性验证所鉴定的CUBN变体，并测试它们在保护肾小球蛋白尿方面的效力。总之，我们的目标是建立一个新的模式，肾脏保护的诊断，预后和治疗蛋白尿性肾病的高度相关性。