Demographic and Clinical Factors Associated With SARS-CoV-2 Spike 1 Antibody Response Among Vaccinated US Adults: the C4R Study.

This study investigates correlates of anti-S1 antibody response following COVID-19 vaccination in a U.S. population-based meta-cohort of adults participating in longstanding NIH-funded cohort studies. Anti-S1 antibodies were measured from dried blood spots collected between February 2021-August 2022 using Luminex-based microsphere immunoassays. Of 6245 participants, mean age was 73 years (range, 21-100), 58% were female, and 76% were non-Hispanic White. Nearly 52% of participants received the BNT162b2 vaccine and 48% received the mRNA-1273 vaccine. Lower anti-S1 antibody levels are associated with age of 65 years or older, male sex, higher body mass index, smoking, diabetes, COPD and receipt of BNT16b2 vaccine (vs mRNA-1273). Participants with a prior infection, particularly those with a history of hospitalized illness, have higher anti-S1 antibody levels. These results suggest that adults with certain socio-demographic and clinical characteristics may have less robust antibody responses to COVID-19 vaccination and could be prioritized for more frequent re-vaccination.

Eculizumab Use in Scleroderma Renal Crisis With Thrombotic Microangiopathy: A Case Report.

A Black woman in her 40s with past medical history significant for obesity treated with Roux-en-Y bypass surgery and a history of Raynaud's phenomenon, presented with acute pulmonary edema secondary to severe malignant hypertension and critically accelerated acute kidney injury, with evidence of systemic microangiopathic hemolytic anemia in the setting of clinical suspicion of systemic sclerosis sine scleroderma. Renin-angiotensin system blockade (angiotensin-converting enzyme inhibitor) was immediately started at the maximum possible dose in the setting of scleroderma renal crisis. Despite better control of blood pressure and volume status, kidney function continued to rapidly decline, thus a decision was made to go ahead with a kidney biopsy on day 3 of admission, which revealed severe features of scleroderma renal crisis with active thrombotic microangiopathy. The multidisciplinary team elected to treat the patient with terminal complement blockade using eculizumab in addition to high dose lisinopril and blood pressure control. Her serum creatinine peaked at 9.3 mg/dL shortly after eculizumab initiation, but improved soon after, dropping to 2.8 mg/dL after completion of the final eculizumab dose and 1.8 mg/dL 3 years later.

Kidney Biopsy Utility: Patient and Clinician Perspectives from the Kidney Precision Medicine Project.

Rationale & Objective: Limited data exist on patient perspectives of the implications of kidney biopsies. We explored patients' perspectives alongside those of clinicians to better understand how kidney biopsies affect patients' viewpoints and the clinical utility of biopsies. Study Design: Prospective Cohort Study. Setting & Participants: Patient participants and clinicians in the Kidney Precision Medicine Project, a prospective cohort study of patients who undergo a research protocol biopsy, at 9 recruitment sites across the United States. Surveys were completed at enrollment before biopsy and additional timepoints after biopsy (participants: 28 days, 6 months; clinicians: 2 weeks). Analytical Approach: Kappa statistics assessed prebiopsy etiology concordance between clinicians and participants. Participant perspectives after biopsy were analyzed using a thematic approach. Clinician ratings of clinical management value were compared to prebiopsy ratings with Wilcoxon matched-pairs signed-rank tests and paired t tests. Results: A total of 167 participants undergoing biopsy (124 participants with chronic kidney disease [CKD], 43 participants with acute kidney injury [AKI]) and 58 clinicians were included in this study. CKD participants and clinicians had low etiology concordance for the 2 leading causes of CKD: diabetes (k = 0.358) and hypertension (k = 0.081). At 28 days postbiopsy, 46 (84%) participants reported that the biopsy affected their understanding of their diagnosis, and 21 (38%) participants reported that the results of the biopsy affected their medications. Participants also shared biopsy impressions in free-text responses, including impacts on lifestyle and concurrent condition management. The biopsy positively shifted clinician perceptions of the procedure's clinical management benefits, while perceptions of prognostic value decreased and diagnostic ratings remained unchanged. Limitations: Our study did not have demographic data of clinicians and could not provide insight into postbiopsy experiences for participants who did not respond to follow-up surveys. Conclusions: Participant perspectives of the personal implications of kidney biopsy can be integrated into shared decision-making between clinicians and patients. Enhanced biopsy reports and interactions between nephrologists and pathologists could augment the management and prognostic value of kidney biopsies. Plain-Language Summary: The utility of kidney biopsy is debated among clinicians, and patients' perspectives are even less explored. To address these gaps, we synthesized perspectives from clinicians and patient participants of the Kidney Precision Medicine Project (KPMP). Both before and after biopsy, clinicians were surveyed on how the procedure affected their clinical management, diagnosis, and prognosis. After biopsy, participants shared how the procedure affected their diagnosis, medication, and lifestyle changes. Clinicians and patients shared an appreciation for the biopsy's impact on medical management but diverged in their takeaways on diagnosis and prognosis. These findings highlight the need for greater collaboration between patients and clinicians, particularly as they navigate shared decision-making when considering kidney biopsy.

Molecular Signatures of Glomerular Neovascularization in a Patient with Diabetic Kidney Disease.

The Kidney Precision Medicine Project (KPMP) aims to create a kidney tissue atlas, define disease subgroups, and identify critical cells, pathways, and targets for novel therapies through molecular investigation of human kidney biopsies obtained from participants with acute kidney injury (AKI) or chronic kidney disease (CKD). We present the case of a 66-year-old woman with diabetic kidney disease who underwent a protocol KPMP kidney biopsy. Her clinical history included diabetes mellitus complicated by neuropathy and eye disease, increased insulin resistance, hypertension, albuminuria, and relatively preserved glomerular filtration rate (early CKD stage 3a). The patient's histopathology was consistent with diabetic nephropathy and arterial and arteriolar sclerosis. Three-dimensional, immunofluorescence imaging of the kidney biopsy specimen revealed extensive peri-glomerular neovascularization that was underestimated by standard histopathologic approaches. Spatial transcriptomics was performed to obtain gene expression signatures at discrete areas of the kidney biopsy. Gene expression in the areas of glomerular neovascularization revealed increased expression of genes involved in angiogenic signaling, proliferation and survival of endothelial cells, as well as new vessel maturation and stability. This molecular correlation provides additional insights into the development of kidney disease in patients with diabetes and spotlights how novel molecular techniques employed by the KPMP can supplement and enrich the histopathologic diagnosis obtained from a kidney biopsy.

PODO: Trial Design: Phase 2 Study of PF-06730512 in Focal Segmental Glomerulosclerosis.

INTRODUCTION: Focal segmental glomerulosclerosis (FSGS) is characterized by proteinuria and a histologic pattern of glomerular lesions of diverse etiology that share features including glomerular scarring and podocyte foot process effacement. Roundabout guidance receptor 2 (ROBO2)/slit guidance ligand 2 (SLIT2) signaling destabilizes the slit diaphragm and reduces podocyte adhesion to the glomerular basement membrane (GBM). Preclinical studies suggest that inhibition of glomerular ROBO2/SLIT2 signaling can stabilize podocyte adhesion and reduce proteinuria. This clinical trial evaluates the preliminary efficacy and safety of ROBO2/SLIT2 inhibition with the ROBO2 fusion protein PF-06730512 in patients with FSGS. METHODS: The Study to Evaluate PF-06730512 in Adults With FSGS (PODO; ClinicalTrials.gov identifier NCT03448692), an open-label, phase 2a, multicenter trial in adults with FSGS, will enroll patients into 2 cohorts (n = 22 per cohort) to receive either high- or low-dose PF-06730512 (intravenous) every 2 weeks for 12 weeks. Key inclusion criteria include a confirmed biopsy diagnosis of FSGS, an estimated glomerular filtration rate (eGFR) ≥45 ml/min/1.73 m2 based on the Chronic Kidney Disease Epidemiology Collaboration formula (30-45 with a recent biopsy), and urinary protein-to-creatinine ratio (UPCR) >1.5 g/g. Key exclusion criteria include collapsing FSGS, serious/active infection, ≥50% tubulointerstitial fibrosis on biopsy, and organ transplantation. The primary endpoint is change from baseline to week 13 in UPCR; secondary endpoints include safety, changes in eGFR, and PF-06730512 serum concentration. RESULTS: This ongoing trial will report the efficacy, safety, pharmacokinetics, and biomarker results of PF-06730512 for patients with FSGS. CONCLUSION: Findings from this proof-of-concept study may support further development and evaluation of PF-06730512 to treat FSGS and warrant assessment in phase 3 clinical trials.

A conceptual framework linking immunology, pathology, and clinical features in primary membranous nephropathy.

Primary membranous nephropathy is a leading cause of adult nephrotic syndrome. The field took a major step forward with the identification of phospholipase A2 receptor (PLA2R) as a target antigen in the majority of cases and with the ability to measure circulating autoantibodies to PLA2R. Since then, the existence of additional target antigens such as thrombospondin type-1 domain-containing 7A, exostosin 1 and 2, neural EGFL like 1, and semaphorin 3B has been demonstrated. The ability to detect and monitor levels of circulating autoantibodies has opened a new window onto the humoral aspect of primary membranous nephropathy. Clinicians now rely on clinical parameters such as proteinuria, as well as levels of circulating autoantibodies against PLA2R and the results of immunofluorescence staining for PLA2R within kidney biopsy tissue, to guide the management of this disease. The relationship between immunologic and clinical disease course is consistent, but not necessarily intuitive. In addition, kidney biopsy provides only a single snapshot of disease that needs to be interpreted in light of changing clinical and serological findings. A clear understanding of these dynamic parameters is essential for staging, treatment, and management of this disease. This review aims to shed light on current knowledge regarding the development and time course of changes in the serum levels of autoantibodies against PLA2R, proteinuria, and histological findings that underlie the pathophysiology of primary membranous nephropathy.

Coincidental crystalline light chain cast nephropathy, light chain proximal tubulopathy, and urine crystallopathy: A case report and review of the literature
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Plasma cell dyscrasias, including multiple myeloma (MM), are associated with diverse forms of pathology in the kidney. Some pathologic lesions, including light chain (myeloma) cast nephropathy (LCCN), are relatively common, while others, such as light chain proximal tubulopathy (LCPT), are less so. Both LCCN and LCPT are associated with clinical manifestations of acute kidney injury. Rare instances of coincidental LCPT and LCCN have been reported, but none to our knowledge of coincidental crystalline forms of these diseases, with similar forms appearing in the urine. While LCPT is usually associated with intracytoplasmic deposition of crystallized light chains, the intraluminal light chain casts in LCCN are typically amorphous and do not form crystals. We report here the co-occurrence of these two monoclonal crystalline forms of acute kidney injury in a 66-year-old woman with known history of κ-restricted multiple myeloma. Additionally, forms suggestive of a crystalline morphology were observed in the urine sediment. Clinicians who observe similar crystalline structures on renal biopsy or in urine sediment should have a high index of suspicion for underlying multiple myeloma as a unifying diagnosis.

Segmentation of Glomeruli Within Trichrome Images Using Deep Learning.

INTRODUCTION: The number of glomeruli and glomerulosclerosis evaluated on kidney biopsy slides constitute standard components of a renal pathology report. Prevailing methods for glomerular assessment remain manual, labor intensive, and nonstandardized. We developed a deep learning framework to accurately identify and segment glomeruli from digitized images of human kidney biopsies. METHODS: Trichrome-stained images (n = 275) from renal biopsies of 171 patients with chronic kidney disease treated at the Boston Medical Center from 2009 to 2012 were analyzed. A sliding window operation was defined to crop each original image to smaller images. Each cropped image was then evaluated by at least 3 experts into 3 categories: (i) no glomerulus, (ii) normal or partially sclerosed (NPS) glomerulus, and (iii) globally sclerosed (GS) glomerulus. This led to identification of 751 unique images representing nonglomerular regions, 611 images with NPS glomeruli, and 134 images with GS glomeruli. A convolutional neural network (CNN) was trained with cropped images as inputs and corresponding labels as output. Using this model, an image processing routine was developed to scan the test images to segment the GS glomeruli. RESULTS: The CNN model was able to accurately discriminate nonglomerular images from NPS and GS images (performance on test data: Accuracy: 92.67% ± 2.02% and Kappa: 0.8681 ± 0.0392). The segmentation model that was based on the CNN multilabel classifier accurately marked the GS glomeruli on the test data (Matthews correlation coefficient = 0.628). CONCLUSION: This work demonstrates the power of deep learning for assessing complex histologic structures from digitized human kidney biopsies.

Association of Pathological Fibrosis With Renal Survival Using Deep Neural Networks.

INTRODUCTION: Chronic kidney damage is routinely assessed semiquantitatively by scoring the amount of fibrosis and tubular atrophy in a renal biopsy sample. Although image digitization and morphometric techniques can better quantify the extent of histologic damage, we need more widely applicable ways to stratify kidney disease severity. METHODS: We leveraged a deep learning architecture to better associate patient-specific histologic images with clinical phenotypes (training classes) including chronic kidney disease (CKD) stage, serum creatinine, and nephrotic-range proteinuria at the time of biopsy, and 1-, 3-, and 5-year renal survival. Trichrome-stained images processed from renal biopsy samples were collected on 171 patients treated at the Boston Medical Center from 2009 to 2012. Six convolutional neural network (CNN) models were trained using these images as inputs and the training classes as outputs, respectively. For comparison, we also trained separate classifiers using the pathologist-estimated fibrosis score (PEFS) as input and the training classes as outputs, respectively. RESULTS: CNN models outperformed PEFS across the classification tasks. Specifically, the CNN model predicted the CKD stage more accurately than the PEFS model (κ = 0.519 vs. 0.051). For creatinine models, the area under curve (AUC) was 0.912 (CNN) versus 0.840 (PEFS). For proteinuria models, AUC was 0.867 (CNN) versus 0.702 (PEFS). AUC values for the CNN models for 1-, 3-, and 5-year renal survival were 0.878, 0.875, and 0.904, respectively, whereas the AUC values for PEFS model were 0.811, 0.800, and 0.786, respectively. CONCLUSION: The study demonstrates a proof of principle that deep learning can be applied to routine renal biopsy images.

Similar Biophysical Abnormalities in Glomeruli and Podocytes from Two Distinct Models.

Background FSGS is a pattern of podocyte injury that leads to loss of glomerular function. Podocytes support other podocytes and glomerular capillary structure, oppose hemodynamic forces, form the slit diaphragm, and have mechanical properties that permit these functions. However, the biophysical characteristics of glomeruli and podocytes in disease remain unclear.Methods Using microindentation, atomic force microscopy, immunofluorescence microscopy, quantitative RT-PCR, and a three-dimensional collagen gel contraction assay, we studied the biophysical and structural properties of glomeruli and podocytes in chronic (Tg26 mice [HIV protein expression]) and acute (protamine administration [cytoskeletal rearrangement]) models of podocyte injury.Results Compared with wild-type glomeruli, Tg26 glomeruli became progressively more deformable with disease progression, despite increased collagen content. Tg26 podocytes had disordered cytoskeletons, markedly abnormal focal adhesions, and weaker adhesion; they failed to respond to mechanical signals and exerted minimal traction force in three-dimensional collagen gels. Protamine treatment had similar but milder effects on glomeruli and podocytes.Conclusions Reduced structural integrity of Tg26 podocytes causes increased deformability of glomerular capillaries and limits the ability of capillaries to counter hemodynamic force, possibly leading to further podocyte injury. Loss of normal podocyte mechanical integrity could injure neighboring podocytes due to the absence of normal biophysical signals required for podocyte maintenance. The severe defects in podocyte mechanical behavior in the Tg26 model may explain why Tg26 glomeruli soften progressively, despite increased collagen deposition, and may be the basis for the rapid course of glomerular diseases associated with severe podocyte injury. In milder injury (protamine), similar processes occur but over a longer time.

Pregnancy in a Patient With Primary Membranous Nephropathy and Circulating Anti-PLA2R Antibodies: A Case Report.

There is little information about pregnancy outcomes in patients with active membranous nephropathy (MN), especially those with circulating autoantibodies to M-type phospholipase A2receptor (PLA2R), the major autoantigen in primary MN. We present what we believe to be the first known case of successful pregnancy in a 39-year-old woman with PLA2R-associated MN. In the year prior to pregnancy, the patient developed anasarca, hypoalbuminemia (albumin, 1.3-2.2g/dL), and proteinuria (protein excretion, 29.2 g/d). Kidney biopsy revealed MN with staining for PLA2R, and the patient was seropositive for anti-PLA2R autoantibodies. She did not respond to conservative therapy and was treated with intravenous rituximab (2 doses of 1 g each). Several weeks after presentation, she was found to be 6 weeks pregnant and was closely followed up without further immunosuppressive treatment. Proteinuria remained with protein excretion in the 8- to 12-g/d range. Circulating anti-PLA2R levels declined but were still detectable. At 38 weeks, a healthy baby girl was born, without proteinuria at birth or at her subsequent 6-month postnatal visit. At the time of delivery, the mother still had detectable circulating anti-PLA2R of immunoglobulin G1 (IgG1), IgG3, and IgG4 subclasses, although at low titers. Only trace amounts of IgG4 anti-PLA2R were found in cord blood. Potential reasons for the discrepancy between anti-PLA2R levels in the maternal and fetal circulation are discussed.

TMIGD1 is a novel adhesion molecule that protects epithelial cells from oxidative cell injury.

Oxidative damage to renal tubular epithelial cells is a fundamental pathogenic mechanism implicated in both acute kidney injury and chronic kidney diseases. Because epithelial cell survival influences the outcome of acute kidney injury and chronic kidney diseases, identifying its molecular regulators could provide new insight into pathobiology and possible new therapeutic strategies for these diseases. We have identified transmembrane and immunoglobulin domain-containing 1 (TMIGD1) as a novel adhesion molecule, which is highly conserved in humans and other species. TMIGD1 is expressed in renal tubular epithelial cells and promotes cell survival. The extracellular domain of TMIGD1 contains two putative immunoglobulin domains and mediates self-dimerization. Our data suggest that TMIGD1 regulates transepithelial electric resistance and permeability of renal epithelial cells. TMIGD1 controls cell migration, cell morphology, and protects renal epithelial cells from oxidative- and nutrient-deprivation-induced cell injury. Hydrogen peroxide-induced oxidative cell injury downregulates TMIGD1 expression and targets it for ubiquitination. Moreover, TMIGD1 expression is significantly affected in both acute kidney injury and in deoxy-corticosterone acetate and sodium chloride (deoxy-corticosterone acetate salt)-induced chronic hypertensive kidney disease mouse models. Taken together, we have identified TMIGD1 as a novel cell adhesion molecule expressed in kidney epithelial cells that protects kidney epithelial cells from oxidative cell injury to promote cell survival.

Perivascular Gli1+ progenitors are key contributors to injury-induced organ fibrosis.

Mesenchymal stem cells (MSCs) reside in the perivascular niche of many organs, including kidney, lung, liver, and heart, although their roles in these tissues are poorly understood. Here, we demonstrate that Gli1 marks perivascular MSC-like cells that substantially contribute to organ fibrosis. In vitro, Gli1(+) cells express typical MSC markers, exhibit trilineage differentiation capacity, and possess colony-forming activity, despite constituting a small fraction of the platelet-derived growth factor-ß (PDGFRß)(+) cell population. Genetic lineage tracing analysis demonstrates that tissue-resident, but not circulating, Gli1(+) cells proliferate after kidney, lung, liver, or heart injury to generate myofibroblasts. Genetic ablation of these cells substantially ameliorates kidney and heart fibrosis and preserves ejection fraction in a model of induced heart failure. These findings implicate perivascular Gli1(+) MSC-like cells as a major cellular origin of organ fibrosis and demonstrate that these cells may be a relevant therapeutic target to prevent solid organ dysfunction after injury.

Early murine polymicrobial sepsis predominantly causes renal injury.

Multiple organ failure in sepsis substantially increases mortality. This study examined if there was greater hepatic, pancreatic, splenic, or renal injury in mice that would die during sepsis induced by cecal ligation and puncture (CLP) compared with that of those that would survive. Mice were stratified into groups predicted to die (Die-P) or predicted to live (Live-P) in the first 5 days after CLP based on plasma interleukin 6 levels. Groups were sacrificed to harvest organs for histology. Separate animals were followed for survival with daily blood sampling to examine renal function. No significant histological evidence of organ injury was observed in either the Live-P or Die-P mice. Minimal hepatic injury occurred as plasma aspartate transaminase demonstrated less than a 2-fold increase over normal in both groups. In addition, pancreatic injury was minimal as there was also less than a 2-fold increase in plasma amylase levels. In contrast, blood urea nitrogen levels were nearly five times higher within 24 h in Die-P mice compared with those of mice predicted to live. Mice with blood urea nitrogen levels higher than 44 mg/dL had a 17.6 higher relative risk of dying (95% confidence interval, 4.5-69.4). Cystatin C, a more specific kidney function biomarker, was also elevated at 24 h after CLP. When the cystatin C levels were analyzed relative to the hours before death, rather than hours after CLP, they were also significantly increased in mice Dead by day 5 compared with those Alive after day 5. We conclude that limited liver, pancreas, and spleen injury develops during murine CLP-induced sepsis while significant kidney injury is present. The renal injury becomes worse closer to death.

Chronic epithelial kidney injury molecule-1 expression causes murine kidney fibrosis.

Acute kidney injury predisposes patients to the development of both chronic kidney disease and end-stage renal failure, but the molecular details underlying this important clinical association remain obscure. We report that kidney injury molecule-1 (KIM-1), an epithelial phosphatidylserine receptor expressed transiently after acute injury and chronically in fibrotic renal disease, promotes kidney fibrosis. Conditional expression of KIM-1 in renal epithelial cells (Kim1(RECtg)) in the absence of an injury stimulus resulted in focal epithelial vacuolization at birth, but otherwise normal tubule histology and kidney function. By 4 weeks of age, Kim1(RECtg) mice developed spontaneous and progressive interstitial kidney inflammation with fibrosis, leading to renal failure with anemia, proteinuria, hyperphosphatemia, hypertension, cardiac hypertrophy, and death, analogous to progressive kidney disease in humans. Kim1(RECtg) kidneys had elevated expression of proinflammatory monocyte chemotactic protein-1 (MCP-1) at early time points. Heterologous expression of KIM-1 in an immortalized proximal tubule cell line triggered MCP-1 secretion and increased MCP-1-dependent macrophage chemotaxis. In mice expressing a mutant, truncated KIM-1 polypeptide, experimental kidney fibrosis was ameliorated with reduced levels of MCP-1, consistent with a profibrotic role for native KIM-1. Thus, sustained KIM-1 expression promotes kidney fibrosis and provides a link between acute and recurrent injury with progressive chronic kidney disease.

Gα12 activation in podocytes leads to cumulative changes in glomerular collagen expression, proteinuria and glomerulosclerosis.

Glomerulosclerosis is a common pathological finding that often progresses to renal failure. The mechanisms of chronic kidney disease progression are not well defined, but may include activation of numerous vasoactive and inflammatory pathways. We hypothesized that podocytes are susceptible to filtered plasma components, including hormones and growth factors that stimulate signaling pathways leading to glomerulosclerosis. Gα12 couples to numerous G-protein-coupled receptors (GPCRs) and regulates multiple epithelial responses, including proliferation, apoptosis, permeability and the actin cytoskeleton. Herein, we report that genetic activation of Gα12 in podocytes leads to time-dependent increases in proteinuria and glomerulosclerosis. To mimic activation of Gα12 pathways, constitutively active Gα12 (QL) was conditionally expressed in podocytes using Nphs2-Cre and LacZ/floxed QLα12 transgenic mice. Some QLα12(LacZ+/Cre+) mice developed proteinuria at 4-6 months, and most were proteinuric by 12 months. Proteinuria increased with age, and by 12-14 months, many demonstrated glomerulosclerosis with ultrastructural changes, including foot process fusion and both mesangial and subendothelial deposits. QLα12(LacZ+/Cre+) mice showed no changes in podocyte number, apoptosis, proliferation or Rho/Src activation. Real-time PCR revealed no significant changes in Nphs1, Nphs2, Cd2ap or Trpc6 expression, but Col4a2 message was increased in younger and older mice, while Col4a5 was decreased in older mice. Confocal microscopy revealed disordered collagen IVα1/2 staining in older mice and loss of α5 without changes in other collagen IV subunits. Taken together, these studies suggest that Gα12 activation promotes glomerular injury without podocyte depletion through a novel mechanism regulating collagen (α)IV expression, and supports the notion that glomerular damage may accrue through persistent GPCR activation in podocytes.

Cytoplasmic Ig alpha serine/threonines fine-tune Ig alpha tyrosine phosphorylation and limit bone marrow plasma cell formation.

Igα serine 191 and 197 and threonine 203, which are located in proximity of the Igα ITAM, dampen Igα ITAM tyrosine phosphorylation. In this study, we show that mice with targeted mutations of Igα S191, 197, and T203 displayed elevated serum IgG2c and IgG2b concentrations and had elevated numbers of IgG2c- and IgG2b-secreting cells in the bone marrow. BCR-induced Igα tyrosine phosphorylation was slightly increased in splenic B cells. Our results suggest that Igα serine/threonines limit formation of IgG2c- and IgG2b-secreting bone marrow plasma cells, possibly by fine-tuning Igα tyrosine-mediated BCR signaling.

Patients with ACTN4 mutations demonstrate distinctive features of glomerular injury.

Mutations in ACTN4, the gene encoding the actin-binding protein alpha-actinin-4, are a cause of familial FSGS. We examined kidney biopsies from patients with ACTN4 mutations to characterize systematically the histopathology of kidney damage in these patients and to determine whether distinctive morphologic changes are associated with mutations in this gene. The changes observed with light microscopy were typical of FSGS and were morphologically heterogeneous, similar to other inherited podocytopathies. The ultrastructural characteristics, however, were distinctive: Most notably, the presence of cytoplasmic electron-dense aggregates in podocytes. Indirect immunofluorescence using antibodies to a conserved domain of alpha-actinin-4 (present in both wild-type and mutant proteins) revealed a segmental and irregular granular staining pattern in the capillary walls of preserved glomeruli of ACTN4 mutants, whereas preserved glomeruli of patients with other podocyte diseases retained a global linear staining pattern for alpha-actinin-4. These characteristics resemble features observed in mouse models of this disease and may aid in the identification of patients and families who harbor ACTN4 mutations.

Lymphoproliferative disease and autoimmunity in mice with increased miR-17-92 expression in lymphocytes.

The genomic region encoding the miR-17-92 microRNA (miRNA) cluster is often amplified in lymphoma and other cancers, and cancer cells carrying this amplification have higher expression of miRNA in this cluster. Retroviral expression of miR-17-92 accelerates c-Myc-induced lymphoma development, but precisely how higher expression of miR-17-92 promotes lymphomagenesis remains unclear. Here we generated mice with higher expression of miR-17-92 in lymphocytes. These mice developed lymphoproliferative disease and autoimmunity and died prematurely. Lymphocytes from these mice showed more proliferation and less activation-induced cell death. The miR-17-92 miRNA suppressed expression of the tumor suppressor PTEN and the proapoptotic protein Bim. This mechanism probably contributed to the lymphoproliferative disease and autoimmunity of miR-17-92-transgenic mice and contributes to lymphoma development in patients with amplifications of the miR-17-92 coding region.

Novel mutations in NPHP4 in a consanguineous family with histological findings of focal segmental glomerulosclerosis.

Nephronophthisis is a form of autosomal recessive hereditary cystic kidney disease that typically progresses to end-stage renal disease by early adulthood. Conversely, focal segmental glomerulosclerosis is a histological glomerular phenotype that can be familial, primary (idiopathic), or secondary to a multitude of pathological processes affecting the kidney, including such tubulointerstitial diseases as nephronophthisis. Mutations in 6 distinct nephronophthisis genes have been described to date. We describe a consanguineous Filipino family with 2 novel sequence variants in the NPHP4 gene. Affected individuals presented with end-stage renal disease and histological features of focal segmental glomerulosclerosis on biopsy. They also had atypical radiological findings, making the clinical diagnosis of the genetic syndrome difficult. Furthermore, although ocular abnormalities and hearing loss were described previously, this is the first report of hepatic disease in patients with mutations in NPHP4. The diagnosis of nephronophthisis was made by means of mutational analysis of the NPHP4 gene after isolation of a region of homozygosity in affected individuals by using whole-genome single-nucleotide polymorphism analysis. Because establishment of the correct diagnosis has implications for therapeutic interventions, prognosis, and, in the case of heritable diseases, appropriate genetic counseling for affected individuals and their families, this report emphasizes the importance of obtaining meticulous clinical information, considering alternative diagnoses, and, when possible, performing genetic evaluation to confirm the diagnosis. We outline an approach to patients with hereditary kidney disease, focusing specifically on the molecular genetic techniques available to evaluate such families and determine a chromosomal region of interest and, subsequently, the diagnosis.