The discovery of >60 monogenic causes of nephrotic syndrome (NS) has revealed a central role for the actin regulators RhoA/Rac1/Cdc42 and their effectors, including the formin INF2. By whole-exome sequencing (WES), we here discovered bi-allelic variants in the formin DAAM2 in four unrelated families with steroid-resistant NS. We show that DAAM2 localizes to the cytoplasm in podocytes and in kidney sections. Further, the variants impair DAAM2-dependent actin remodeling processes: wild-type DAAM2 cDNA, but not cDNA representing missense variants found in individuals with NS, rescued reduced podocyte migration rate (PMR) and restored reduced filopodia formation in shRNA-induced DAAM2-knockdown podocytes. Filopodia restoration was also induced by the formin-activating molecule IMM-01. DAAM2 also co-localizes and co-immunoprecipitates with INF2, which is intriguing since variants in both formins cause NS. Using in vitro bulk and TIRF microscopy assays, we find that DAAM2 variants alter actin assembly activities of the formin. In a Xenopus daam2-CRISPR knockout model, we demonstrate actin dysregulation in vivo and glomerular maldevelopment that is rescued by WT-DAAM2 mRNA. We conclude that DAAM2 variants are a likely cause of monogenic human SRNS due to actin dysregulation in podocytes. Further, we provide evidence that DAAM2-associated SRNS may be amenable to treatment using actin regulating compounds.

的肾病综合征（NS）的> 60个单基因原因发现已经揭示了肌动蛋白调节的RhoA / Rac1的/ Cdc42和它们的效应，包括formin中心作用INF2。通过全外显子组测序（WES），我们在四个具有类固醇抗性 NS 的无关家族中发现了 formin DAAM2中的双等位基因变异。我们显示 DAAM2 定位于足细胞和肾脏切片中的细胞质。此外，这些变异会损害DAAM2依赖的肌动蛋白重塑过程：野生型DAAM2 cDNA，但不是代表 NS 患者中发现的错义变异的 cDNA，挽救了降低的足细胞迁移率 (PMR) 并恢复了 shRNA 诱导的DAAM2 中减少的丝状伪足形成- 击倒足细胞。丝状伪足的恢复也由福明激活分子 IMM-01 诱导。DAAM2 还与 INF2 共定位和共免疫沉淀，这很有趣，因为两种形式的变异都会导致 NS。使用体外散装和全内反射荧光显微镜分析，我们发现，d AAM 2变种的formin的ALTER肌动蛋白装配活动。在非洲爪蟾daam2- CRISPR敲除模型中，我们证明了WT- DAAM2 mRNA挽救的体内肌动蛋白失调和肾小球发育不良。我们得出结论，由于足细胞中肌动蛋白失调，DAAM2变体可能是单基因人类 SRNS 的原因。此外，我们提供证据表明DAAM2相关的 SRNS 可能适合使用肌动蛋白调节化合物进行治疗。