Disruption of glomerular basement membrane charge through podocyte-specific mutation of agrin does not alter glomerular permselectivity
Disruption of glomerular basement membrane charge through podocyte-specific mutation of agrin does not alter glomerular permselectivity
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DOI：
10.2353/ajpath.2007.061116
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发表时间：
2007-07-01
影响因子：
6
通讯作者：
Miner, Jeffrey H.
中科院分区：
文献类型：
--
作者：
Harvey, Scott J.;Jarad, George;Miner, Jeffrey H.
肾小球电荷选择性归因于阴离子硫酸乙酰肝素蛋白聚糖； (HSPGS) 存在于肾小球基底膜 (GBM) 中。 Agrin 是主要的 GBM-HSPG，但缺乏证据表明它有助于电荷屏障，因为新生的 Agrin 缺陷小鼠会死于神经肌肉缺陷。为了研究成人肾脏中的集聚蛋白，使用一种新的条件等位基因来产生足细胞特异性敲除。突变体在 9 个月大时仍能存活并且没有表现出肾脏组织病理学变化。 Perlecan是一种HSPG，通常局限于成熟肾小球的系膜，但它没有出现在缺乏硫酸乙酰肝素的突变GBM中。此外，发现GBM集聚蛋白主要源自足细胞。胎儿肾脏的聚乙烯亚胺标记揭示了沿着GBM的两个稀层的阴离子位点，这些位点在成熟时沿着上皮下方面变得最突出；在集聚蛋白缺陷和条件性基因敲除小鼠中，沿着上皮下方面的标记大大减少。尽管电荷受到严重破坏，但肾小球滤过屏障并未受到损害，即使面临牛血清白蛋白过载的挑战。我们的结论是，GBM 架构的建立或维护不需要 agrin。尽管集聚蛋白对 GBM 的阴离子电荷有显着贡献，但它及其电荷都不是肾小球选择性通透性所必需的。这让人质疑电荷选择性是否是 GBM 的一个特征。
Glomerular charge selectivity has been attributed to anionic heparan sulfate proteoglycans; (HSPGS) in the glomerular basement membrane (GBM). Agrin is the predominant GBM-HSPG, but evidence that it contributes to the charge barrier is lacking, because newborn agrin-deficient mice die from neuromuscular defects. To study agrin in adult kidney, a new conditional allele was used to generate podocyte-specific knockouts. Mutants were viable and displayed no renal histopathology up to 9 months of age. Perlecan, a HSPG normally confined to the mesangium in mature glomeruli, did not appear in the mutant GBM, which lacked heparan sulfate. Moreover, GBM agrin was found to be derived primarily from podocytes. Polyethyleneimine labeling of fetal kidneys revealed anionic sites along both laminae rarae of the GBM that became most prominent along the subepithelial aspect at maturity;, labeling was greatly reduced along the subepithelial aspect in agrin-deficient and conditional knockout mice. Despite this severe charge disruption, the glomerular filtration barrier was not compromised, even when challenged with bovine serum albumin overload. We conclude that agrin is not required for establishment or maintenance of GBM architecture. Although agrin contributes significantly to the anionic charge to the GBM, both it and its charge are not needed for glomerular permselectivity. This calls into question whether charge selectivity is a feature of the GBM.