Yang Huihui, Zhu Gaohong, Shao Wenjun, Liao Panli, Yan Yuan, Wang Chun, Wang Xiaowen
Department of Nephrology, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Center), Tongji Medical College, Huazhong University of Science & Technology, Wuhan, China.
State Key Laboratory of Oral & Maxillofacial Reconstruction and Regeneration, Key Laboratory of Oral Biomedicine Ministry of Education, Hubei Key Laboratory of Stomatology, School & Hospital of Stomatology, Wuhan University, Wuhan, China.
Pediatr Nephrol. 2025 May;40(5):1663-1676. doi: 10.1007/s00467-024-06618-9. Epub 2025 Jan 16.
Steroid-resistant nephrotic syndrome (SRNS) is insensitive to steroid therapy and overwhelmingly progresses to kidney failure (KF), the known pathogenic genes of which include key subunits of the nuclear pore complex (NPC), a less-recognized contributor to glomerular podocyte injury.
After analyzing their clinical characterizations and obtaining parental consent, whole-exome sequencing (WES) was performed on patients with SRNS. Several nucleoporin (NUP) biallelic pathogenic variants were identified and further analyzed by cDNA-PCR sequencing from white cells of peripheral blood, minigene assay, immunohistochemical (IHC) staining, and electron microscopy (EM) ultrastructure observation of kidney biopsy, as well as multiple in silico prediction tools, including 3D protein modeling.
Here, in six families with SRNS, we identified pathogenic mutations in NUP85/93/107/160 genes. Specifically, the patient with NUP93 mutation developed KF six months after diagnosis at 1 year 2 months. Two missense mutations, c.1655A > G and c.1604A > C, disrupted the protein stability of NUP93 by IHC staining of kidney biopsy. Ultrastructurally, the above mutations led to severe vacuolization and deformed nucleus in podocytes, torn and dissolved glomerular basement membrane, and diffuse foot process effacement. The patient with NUP85 mutation reached chronic kidney disease (CKD) stage 3 after 4 years follow-up, with exons 2-5 in-frame loss and a missense variant at c.511C > T, not affecting NUP85 expression but possibly weakened interaction with Seh1. Additionally, an extended endoplasmic reticulum (ER) tubule was readily observed under EM. Meanwhile, dilated ER was also found in two children with NUP160 mutations (c.3330 delA and c.2407 G > A; c.2241 + 1 (IVS17) G > T and c.3656 T > G), one of which has undergone kidney transplantation. Compound heterozygous variants in NUP107, c.1695 G > C and c.1360 C > T, were found in a 14-year-old girl initially diagnosed with CKD stage 5, with the former variant causing exon 19 skipping and early translation termination. c.1311 + 1(IVS15) G > A and c.1790 C > T were identified in the second affected girl, with the former causing exon 15 skipping and an in-frame loss of aa417-438, which disrupted the stability of NUP107 and interaction with NUP133.
Our findings expand the spectrum of phenotypes and genotypes of NUPs-associated SRNS and suggest its possible pathogenic mechanism in nuclear and ER homeostasis.
激素抵抗型肾病综合征（SRNS）对激素治疗不敏感，绝大多数会进展为肾衰竭（KF），其已知致病基因包括核孔复合体（NPC）的关键亚基，这是肾小球足细胞损伤中一个较少被认识的因素。
在分析患者的临床特征并获得家长同意后，对SRNS患者进行全外显子测序（WES）。鉴定出几个核孔蛋白（NUP）双等位基因致病性变异，并通过外周血白细胞的cDNA - PCR测序、小基因检测、免疫组织化学（IHC）染色、肾活检的电子显微镜（EM）超微结构观察以及多种计算机预测工具（包括3D蛋白质建模）进行进一步分析。
在此，在6个SRNS家庭中，我们在NUP85/93/107/160基因中鉴定出致病性突变。具体而言，携带NUP93突变的患者在1岁2个月诊断后6个月发展为KF。通过肾活检的IHC染色，两个错义突变c.1655A＞G和c.1604A＞C破坏了NUP93的蛋白质稳定性。超微结构上，上述突变导致足细胞严重空泡化和细胞核变形、肾小球基底膜撕裂和溶解以及弥漫性足突消失。携带NUP85突变的患者在随访4年后达到慢性肾脏病（CKD）3期，外显子2 - 5框内缺失以及c.511C＞T处的错义变异，不影响NUP85表达，但可能削弱与Seh1的相互作用。此外，在EM下很容易观察到内质网（ER）小管延长。同时，在两个携带NUP160突变（c.3330 delA和c.2407 G＞A；c.2241 + 1（IVS17）G＞T和c.3656 T＞G）的儿童中也发现了扩张的ER，其中一名儿童已接受肾移植。在一名最初诊断为CKD 5期的14岁女孩中发现了NUP107的复合杂合变异c.1695 G＞C和c.1360 C＞T，前一个变异导致外显子19跳跃和早期翻译终止。在第二个受影响的女孩中鉴定出c.1311 + 1（IVS15）G＞A和c.1790 C＞T，前者导致外显子15跳跃和aa417 - 438的框内缺失，这破坏了NUP107的稳定性以及与NUP133的相互作用。
我们的发现扩展了与NUP相关的SRNS的表型和基因型谱，并提示其在核和内质网稳态中的可能致病机制。
