Jia Rao

Mutations in nuclear pore genes NUP93, NUP205 and XPO5 cause steroid-resistant nephrotic syndrome

Nucleoporins are essential components of the nuclear pore complex (NPC). Only a few diseases have been attributed to NPC dysfunction. Steroid-resistant nephrotic syndrome (SRNS), a frequent cause of chronic kidney disease, is caused by dysfunction of glomerular podocytes. Here we identify in eight families with SRNS mutations in NUP93, its interaction partner NUP205 or XPO5 (encoding exportin 5) as hitherto unrecognized monogenic causes of SRNS. NUP93 mutations caused disrupted NPC assembly. NUP93 knockdown reduced the presence of NUP205 in the NPC, and, reciprocally, a NUP205 alteration abrogated NUP93 interaction. We demonstrate that NUP93 and exportin 5 interact with the signaling protein SMAD4 and that NUP93 mutations abrogated interaction with SMAD4. Notably, NUP93 mutations interfered with BMP7-induced SMAD transcriptional reporter activity. We hereby demonstrate that mutations of NUP genes cause a distinct renal disease and identify aberrant SMAD signaling as a new disease mechanism of SRNS, opening a potential new avenue for treatment.

Mutations in sphingosine-1-phosphate lyase cause nephrosis with ichthyosis and adrenal insufficiency

Steroid-resistant nephrotic syndrome (SRNS) causes 15% of chronic kidney disease cases. A mutation in 1 of over 40 monogenic genes can be detected in approximately 30% of individuals with SRNS whose symptoms manifest before 25 years of age. However, in many patients, the genetic etiology remains unknown. Here, we have performed whole exome sequencing to identify recessive causes of SRNS. In 7 families with SRNS and facultative ichthyosis, adrenal insufficiency, immunodeficiency, and neurological defects, we identified 9 different recessive mutations in SGPL1, which encodes sphingosine-1-phosphate (S1P) lyase. All mutations resulted in reduced or absent SGPL1 protein and/or enzyme activity. Overexpression of cDNA representing SGPL1 mutations resulted in subcellular mislocalization of SGPL1. Furthermore, expression of WT human SGPL1 rescued growth of SGPL1-deficient dpl1&Dgr; yeast strains, whereas expression of disease-associated variants did not. Immunofluorescence revealed SGPL1 expression in mouse podocytes and mesangial cells. Knockdown of Sgpl1 in rat mesangial cells inhibited cell migration, which was partially rescued by VPC23109, an S1P receptor antagonist. In Drosophila, Sply mutants, which lack SGPL1, displayed a phenotype reminiscent of nephrotic syndrome in nephrocytes. WT Sply, but not the disease-associated variants, rescued this phenotype. Together, these results indicate that SGPL1 mutations cause a syndromic form of SRNS.

Accuracy of Early DMSA Scan for VUR in Young Children With Febrile UTI

OBJECTIVE: To evaluate the accuracy of an acute 99mTc-dimercaptosuccinic acid (DMSA) scan in predicting dilating vesicoureteral reflux (VUR) among young children with a febrile urinary tract infection (UTI). METHODS: The medical records of children (≤2 years of age), presenting with febrile UTI between January 2000 and December 2011, were retrospectively reviewed. RESULTS: A total of 523 children were included in this study, of whom 397 children (75.9%) had abnormal DMSA results and 178 children (34.0%) were identified as VUR on micturating cystourethrography (MCU). Among all the patients, the number of children with dilating VUR was 151 (28.9%). The rate of abnormal results on DMSA for the dilating VUR group was significantly higher than the rates for the non-VUR and low-grade VUR groups (P < .01). In the <6 months age group and ≥6 months age group, the sensitivities of DMSA in predicting dilating VUR were 96.15% and 100.0%, respectively, the negative predictive values were 97.26% and 100.0%, respectively, and the negative likelihood ratios were 0.0911 and 0.0000, respectively. CONCLUSION: For children ≤2 years of age with a febrile UTI, an acute DMSA scan is valuable in the exclusion of dilating VUR. The likelihood of the presence of dilating VUR on MCU is rather low when the result of DMSA is negative. DMSA should be conducted to assess the need for an MCU.

Angiopoietin-like 3 induces podocyte F-actin rearrangement through integrin α(V)β₃/FAK/PI3K pathway-mediated Rac1 activation.

Glomerular podocytes are highly differentiated cells whose foot processes, which are mainly maintained by the architecture of actin filaments, have a unique morphology. A rearrangement of F-actin in podocytes causes changes in their motility that involve foot process effacement and proteinuria in glomerular diseases. Members of the Rho family small GTPases, especially RhoA, Rac1, and Cdc42, are key molecules in the regulation of actin cytoskeleton rearrangement. Our previous study showed that angiopoietin-like 3 (Angptl3) can increase the motility of podocytes in vitro. In this study, we found that recombinant Angptl3 treatment, together with the activation of Rac1, could cause F-actin rearrangement in podocytes. We also found that these effects could be blocked by an integrin α V β 3 inhibitor, implicating integrin α V β 3 as the Angptl3 receptor in its effects on actin cytoskeleton rearrangement. In addition, we studied the molecular pathway for this process. Our results showed that in podocytes, Angptl3 could induce actin filament rearrangement, mainly in lamellipodia formation, and that this process was mediated by integrin α V β 3-mediated FAK and PI3K phosphorylation and Rac1 activation. Our results might provide a new explanation for the effect of Angptl3 on increasing podocyte motility.

Efficacy of rituximab therapy in children with refractory nephrotic syndrome: a prospective observational study in Shanghai

BackgroundIdiopathic nephrotic syndrome is the most common glomerular disease in children. This study was undertaken to observe the efficacy and side-effects of rituximab (RTX) in treating children with different types of refractory primary nephrotic syndrome.MethodsTwelve patients with steroid dependent nephrotic syndrome (SDNS), frequently relapsing nephritic syndrome (FRNS), and steroid resistant nephrotic syndrome (SRNS) were enrolled in our study. There were obvious drug side-effects, and proteinuria remained difficult to control. RTX was administered at a dose of 375 mg/m2 body surface area, once or twice weekly.ResultsThe male to female ratio was 3:1, and the onset age was 1.6–8.9 years. There were 9 patients with steroid sensitive nephrotic syndrome (SDNS or FRNS), and 3 patients with SRNS. There were 7 patients with minimal change disease (MCD), 3 patients with focal segmental glomerular sclerosis (FSGS), 1 with focal proliferative glomerulonephritis, and 1 without renal biopsy. The total effective treatment rate of RTX was 91.67%, and for 77.78% of the patients, steroid dosage could be reduced. Six months before and after RTX infusion, the mean steroid dosage was significantly decreased (P=0.014) and the recurrence number was significantly reduced (P<0.001). The results were better in MCD patients than in FSGS patients (P=0.045). There was no significant difference between FRNS/SDNS and SRNS patients (P=0.175). During RTX administration, 3 patients developed skin rashes, 1 developed hypotension, and 1 developed a fever. One patient experienced a persistent decrease in serum immunoglobulin level but without serious infection.ConclusionRTX was effective in the treatment of refractory nephrotic syndrome, and it could significantly reduce the use of steroid and immunosuppressants.

Efficacy of urine screening at school: experience in Shanghai, China

To explore the prevalence of hematuria or proteinuria in school children in Shanghai and to evaluate the screening methods, we conducted urine screening in more than 40,000 school children between 2003 and 2005. Children were tested with dipsticks read manually (method A) or dipsticks read by machines (method B) combined with a sulfosalicylic acid test or microscopy. Some children were tested once, and others who had abnormal results in the first screening were tested again 2xa0weeks later. The prevalence of urine abnormalities in the first screening was more than 5.00% and of the second screening about 1.00%. Either method B or testing two urine samples for each child had higher specificity. As to the direct cost, that of screening twice with method A was lower than just screening once with method B. So using method A to screen twice for each child was not only convenient and economical, but also could reduce the false positive rate effectively. More than 10xa0months of follow-up diagnosed two cases of IgA nephropathy. Asymptomatic chronic renal diseases in school children could be detected through school urine screening. For Shanghai, China, screening twice using method A might be the best choice.

Whole Exome Sequencing of Patients with Steroid-Resistant Nephrotic Syndrome

BACKGROUND AND OBJECTIVESnSteroid-resistant nephrotic syndrome overwhelmingly progresses to ESRD. More than 30 monogenic genes have been identified to cause steroid-resistant nephrotic syndrome. We previously detected causative mutations using targeted panel sequencing in 30% of patients with steroid-resistant nephrotic syndrome. Panel sequencing has a number of limitations when compared with whole exome sequencing. We employed whole exome sequencing to detect monogenic causes of steroid-resistant nephrotic syndrome in an international cohort of 300 families.nnnDESIGN, SETTING, PARTICIPANTS, & MEASUREMENTSnThree hundred thirty-five individuals with steroid-resistant nephrotic syndrome from 300 families were recruited from April of 1998 to June of 2016. Age of onset was restricted to <25 years of age. Exome data were evaluated for 33 known monogenic steroid-resistant nephrotic syndrome genes.nnnRESULTSnIn 74 of 300 families (25%), we identified a causative mutation in one of 20 genes known to cause steroid-resistant nephrotic syndrome. In 11 families (3.7%), we detected a mutation in a gene that causes a phenocopy of steroid-resistant nephrotic syndrome. This is consistent with our previously published identification of mutations using a panel approach. We detected a causative mutation in a known steroid-resistant nephrotic syndrome gene in 38% of consanguineous families and in 13% of nonconsanguineous families, and 48% of children with congenital nephrotic syndrome. A total of 68 different mutations were detected in 20 of 33 steroid-resistant nephrotic syndrome genes. Fifteen of these mutations were novel. NPHS1, PLCE1, NPHS2, and SMARCAL1 were the most common genes in which we detected a mutation. In another 28% of families, we detected mutations in one or more candidate genes for steroid-resistant nephrotic syndrome.nnnCONCLUSIONSnWhole exome sequencing is a sensitive approach toward diagnosis of monogenic causes of steroid-resistant nephrotic syndrome. A molecular genetic diagnosis of steroid-resistant nephrotic syndrome may have important consequences for the management of treatment and kidney transplantation in steroid-resistant nephrotic syndrome.

A vital role for Angptl3 in the PAN-induced podocyte loss by affecting detachment and apoptosis in vitro

BackgroundPodocyte detachment and apoptosis are two risk factors causing podocyte loss, F-actin rearrangement is involved in detachment and apoptosis. However, the nature of events that promote detachment and apoptosis of podocytes and whether detachment occurred simultaneously with apoptosis are still unclear. Previously, it was found that angiopoietin-like3 (Angptl3) induces F-actin rearrangement in podocytes. In this study we investigate whether Angptl3 influences podocyte loss (detachment and apoptosis) and the process through which Angptl3 exactly influenced the podocyte loss.MethodsIn conditionally immortalized mice podocytes, recombinant mice Angptl3 protein (rm-Angptl3) was used to mimic Angptl3 overexpression model and transfection with small interfering RNA (siRNA) to knockdown the expression of Angptl3. Both flow cytometry analysis and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay were used to detect apoptosis. Rearrangement of F-actin was assessed using confocal microscopy. Western blot assay was used to measure levels of Angptl3, integrin α3β1, integrin-linked kinase (ILK), p53, caspase 3, and phosphorylation of integrin β1.ResultsIn a puromycin aminonucleoside (PAN)-induced podocyte injury model, rm-Angptl3 accelerated the loss of podocytes, both detachment and apoptosis occurred, and F-actin rearrangement is involved in the process. However, knockdown of Angptl3 by siRNA markedly ameliorated these injuries. Observed effects were partially correlated with the altered integrin α3β1, ILK and p53, rather than caspase 3.ConclusionsAngptl3 is a novel factor involved in the PAN-induced podocyte loss by affecting detachment and apoptosis in vitro. This study helps to deepen the understanding of the mechanisms of podocyte loss and lays the foundation for developing a new successful therapy for podocyte injury via lower expression of Angptl3.

Mutations in six nephrosis genes delineate a pathogenic pathway amenable to treatment

No efficient treatment exists for nephrotic syndrome (NS), a frequent cause of chronic kidney disease. Here we show mutations in six different genes (MAGI2, TNS2, DLC1, CDK20, ITSN1, ITSN2) as causing NS in 17 families with partially treatment-sensitive NS (pTSNS). These proteins interact and we delineate their roles in Rho-like small GTPase (RLSG) activity, and demonstrate deficiency for mutants of pTSNS patients. We find that CDK20 regulates DLC1. Knockdown of MAGI2, DLC1, or CDK20 in cultured podocytes reduces migration rate. Treatment with dexamethasone abolishes RhoA activation by knockdown of DLC1 or CDK20 indicating that steroid treatment in patients with pTSNS and mutations in these genes is mediated by this RLSG module. Furthermore, we discover ITSN1 and ITSN2 as podocytic guanine nucleotide exchange factors for Cdc42. We generate Itsn2-L knockout mice that recapitulate the mild NS phenotype. We, thus, define a functional network of RhoA regulation, thereby revealing potential therapeutic targets.Nephrotic syndrome is the second most common chronic kidney disease but there are no targeted treatment strategies available. Here the authors identify mutations of six genes codifying for proteins involved in cytoskeleton remodelling and modulation of small GTPases in 17 families with nephrotic syndrome.

Renal histological features of school-age children with asymptomatic haematuria and/or proteinuria: a multicenter study.

The risk of asymptomatic haematuria and/or proteinuria development into chronic progressive glomerulonephritis (CPG) is unclear. The indications for renal biopsy and follow‐up on these asymptomatic children remain controversial.