The Nephrotic Syndrome Study Network (NEPTUNE) is a North American multi-center collaborative consortium established to develop a translational research infrastructure for Nephrotic Syndrome. This includes a longitudinal observational cohort study, a pilot and ancillary studies program, a training program, and a patient contact registry. NEPTUNE will enroll 450 adults and children with minimal change disease, focal segmental glomerulosclerosis and membranous nephropathy for detailed clinical, histopathologic, and molecular phenotyping at the time of clinically-indicated renal biopsy. Initial visits will include an extensive clinical history, physical examination, collection of urine, blood and renal tissue samples, and assessments of quality of life and patient-reported outcomes. Follow-up history, physical measures, urine and blood samples, and questionnaires will be obtained every 4 months in the first year and bi-annually, thereafter. Molecular profiles and gene expression data will be linked to phenotypic, genetic, and digitalized histologic data for comprehensive analyses using systems biology approaches. Analytical strategies were designed to transform descriptive information to mechanistic disease classification for Nephrotic Syndrome and to identify clinical, histological, and genomic disease predictors. Thus, understanding the complexity of the disease pathogenesis will guide further investigation for targeted therapeutic strategies.

The calcium-activated K + channel KCa3.1 plays an important role in T lymphocyte Ca 2+ signaling by helping to maintain a negative membrane potential, which provides an electrochemical gradient to drive Ca 2+ influx. To assess the role of KCa3.1 channels in lymphocyte activation in vivo, we studied T cell function in KCa3.1 −/− mice. CD4 T helper (i.e., Th0) cells isolated from KCa3.1 −/− mice lacked KCa3.1 channel activity, which resulted in decreased T cell receptor–stimulated Ca 2+ influx and IL-2 production. Although loss of KCa3.1 did not interfere with CD4 T cell differentiation, both Ca 2+ influx and cytokine production were impaired in KCa3.1 −/− Th1 and Th2 CD4 T cells, whereas T-regulatory and Th17 function were normal. We found that inhibition of KCa3.1 −/− protected mice from developing severe colitis in two mouse models of inflammatory bowel disease, which were induced by ( i ) the adoptive transfer of mouse naïve CD4 T cells into rag2 −/− recipients and ( ii ) trinitrobenzene sulfonic acid. Pharmacologic inhibitors of KCa3.1 have already been shown to be safe in humans. Thus, if these preclinical studies continue to show efficacy, it may be possible to rapidly test whether KCa3.1 inhibitors are efficacious in patients with inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis.

Expression quantitative trait loci (eQTL) studies illuminate the genetics of gene expression and, in disease research, can be particularly illuminating when using the tissues directly impacted by the condition. In nephrology, there is a paucity of eQTL studies of human kidney. Here, we used whole-genome sequencing (WGS) and microdissected glomerular (GLOM) and tubulointerstitial (TI) transcriptomes from 187 individuals with nephrotic syndrome (NS) to describe the eQTL landscape in these functionally distinct kidney structures. Using MatrixEQTL, we performed cis-eQTL analysis on GLOM (n = 136) and TI (n = 166). We used the Bayesian "Deterministic Approximation of Posteriors" (DAP) to fine-map these signals, eQTLBMA to discover GLOM- or TI-specific eQTLs, and single-cell RNA-seq data of control kidney tissue to identify the cell type specificity of significant eQTLs. We integrated eQTL data with an IgA Nephropathy (IgAN) GWAS to perform a transcriptome-wide association study (TWAS). We discovered 894 GLOM eQTLs and 1,767 TI eQTLs at FDR < 0.05. 14% and 19% of GLOM and TI eQTLs, respectively, had >1 independent signal associated with its expression. 12% and 26% of eQTLs were GLOM specific and TI specific, respectively. GLOM eQTLs were most significantly enriched in podocyte transcripts and TI eQTLs in proximal tubules. The IgAN TWAS identified significant GLOM and TI genes, primarily at the HLA region. In this study, we discovered GLOM and TI eQTLs, identified those that were tissue specific, deconvoluted them into cell-specific signals, and used them to characterize known GWAS alleles. These data are available for browsing and download via our eQTL browser, "nephQTL."

The calcium activated K ؉ channel KCa3.1 plays an important role in T lymphocyte Ca 2؉ signaling by helping to maintain a negative membrane potential, which provides an electrochemical gradient to drive Ca 2؉ influx. We previously showed that nucleoside diphosphate kinase beta (NDPK-B), a mammalian histidine kinase, is required for KCa3.1 channel activation in human CD4 T lymphocytes. We now show that the mammalian protein histidine phosphatase (PHPT-1) directly binds and inhibits KCa3.1 by dephosphorylating histidine 358 on KCa3.1. Overexpression of wild-type, but not a phosphatase dead, PHPT-1 inhibited KCa3.1 channel activity. Decreased expression of PHPT-1 by siRNA in human CD4 T cells resulted in an increase in KCa3.1 channel activity and increased Ca 2؉ influx and proliferation after T cell receptor (TCR) activation, indicating that endogenous PHPT-1 functions to negatively regulate CD4 T cells. Our findings provide a previously unrecognized example of a mammalian histidine phosphatase negatively regulating TCR signaling and are one of the few examples of histidine phosphorylation/dephosphorylation influencing a biological process in mammals.nucleoside diphosphate kinase ͉ NM23-h2 ͉ PHPT-1 ͉ CRAC channel ͉ histidine kinase

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MiRNAs have been shown to play key roles in both the function and differentiation of a number of different cell types. Drosha and Dicer, two RNAase III enzymes, function in a stepwise manner to generate a mature miRNA. Previous studies have demonstrated that podocyte-specific deletion of Dicer during development results in a collapsing glomerulopathy (CG). However these studies did not address whether miRNAs are required for the normal function of a mature podocytes throughout life. In addition, Dicer has functions other than generation of miRNAs. We now show that a podocyte-specific deletion of Drosha results in a similar phenotype to Dicer mutants confirming that the Dicer mutant phenotype is due to the loss of miRNAs. Moreover, we demonstrate that inducible deletion of Drosha in 2–3 month old mice results in a CG, thereby demonstrating for the first time that miRNAs are required for the normal function of mature podocytes. The finding that loss of miRNAs in mature podocytes leads to a CG is consistent with the idea that changes in specific miRNAs in the various podocytopathies may directly mediate disease, and suggests that identifying these miRNAs will provide new insight into disease pathogenesis and novel therapeutic targets.

Background We evaluated and compared the effects of sparsentan, a dual endothelin type A (ET A) and angiotensin II type 1 receptor antagonist, with those of the angiotensin II type 1 receptor antagonist irbesartan in patients with primary FSGS. Methods In this phase 2, randomized, double-blind, active-control Efficacy and Safety of Sparsentan (RE-021), a Dual Endothelin Receptor and Angiotensin Receptor Blocker, in Patients with Focal Segmental Glomerulosclerosis (FSGS): A Randomized, Double-blind, Active-Control, Dose-Escalation Study (DUET), patients aged 8-75 years with biopsy-proven FSGS, eGFR.30 ml/min per 1.73 m 2 , and urinary protein-to-creatinine ratio (UP/C) $1.0 g/g received sparsentan (200, 400, or 800 mg/d) or irbesartan (300 mg/d) for 8 weeks, followed by open-label sparsentan only. End points at week 8 were reduction from baseline in UP/C (primary) and proportion of patients achieving FSGS partial remission end point (FPRE) (UP/C: #1.5 g/g and .40% reduction [secondary]). Results Of 109 patients randomized, 96 received study drugs and had baseline and week 8 UP/C measurements. Sparsentan-treated patients had greater reductions in UP/C than irbesartan-treated patients did when all doses (45% versus 19%; P=0.006) or the 400 and 800 mg doses (47% versus 19%; P=0.01) were pooled for analysis. The FSGS partial remission end point was achieved in 28% of sparsentan-treated and 9% of irbesartan-treated patients (P=0.04). After 8 weeks of treatment, BP was reduced with sparsentan but not irbesartan, and eGFR was stable with both treatments. Overall, the incidence of adverse events was similar between groups. Hypotension and edema were more common among sparsentan-treated patients but did not result in study withdrawals. Conclusions Patients with FSGS achieved significantly greater reductions in proteinuria after 8 weeks of sparsentan versus irbesartan. Sparsentan was safe and well tolerated.

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