Early involvement of cellular stress and inflammatory signals in the pathogenesis of tubulointerstitial kidney disease due to UMOD mutations

Proteomic insights into the pathophysiology of hypertension-associated albuminuria: Pilot study in a South African cohort

BACKGROUND

Hypertension is an important public health priority with a high prevalence in Africa. It is also an independent risk factor for kidney outcomes. We aimed to identify potential proteins and pathways involved in hypertension-associated albuminuria by assessing urinary proteomic profiles in black South African participants with combined hypertension and albuminuria compared to those who have neither condition.

METHODS

The study included 24 South African cases with both hypertension and albuminuria and 49 control participants who had neither condition. Protein was extracted from urine samples and analysed using ultra-high-performance liquid chromatography coupled with mass spectrometry. Data were generated using data-independent acquisition (DIA) and processed using Spectronaut™ 15. Statistical and functional data annotation were performed on Perseus and Cytoscape to identify and annotate differentially abundant proteins. Machine learning was applied to the dataset using the OmicLearn platform.

RESULTS

Overall, a mean of 1,225 and 915 proteins were quantified in the control and case groups, respectively. Three hundred and thirty-two differentially abundant proteins were constructed into a network. Pathways associated with these differentially abundant proteins included the immune system (q-value [false discovery rate] = 1.4 × 10- 45), innate immune system (q = 1.1 × 10- 32), extracellular matrix (ECM) organisation (q = 0.03) and activation of matrix metalloproteinases (q = 0.04). Proteins with high disease scores (76-100% confidence) for both hypertension and chronic kidney disease included angiotensinogen (AGT), albumin (ALB), apolipoprotein L1 (APOL1), and uromodulin (UMOD). A machine learning approach was able to identify a set of 20 proteins, differentiating between cases and controls.

CONCLUSIONS

The urinary proteomic data combined with the machine learning approach was able to classify disease status and identify proteins and pathways associated with hypertension-associated albuminuria.

The Versatile Role of Uromodulin in Renal Homeostasis and Its Relevance in Chronic Kidney Disease

Uromodulin, also known as the Tamm-Horsfall protein, is predominantly expressed in epithelial cells of the kidney. It is secreted mainly in the urine, although small amounts are also found in serum. Uromodulin plays an important role in maintaining renal homeostasis, particularly in salt/water transport mechanisms and is associated with salt-sensitive hypertension. It also regulates urinary tract infections, kidney stones, and the immune response in the kidneys or extrarenal organs. Uromodulin has been shown to be associated with the renal function, age, nephron volume, and metabolic abnormalities and has been proposed as a novel biomarker for the tubular function or injury. These findings suggest that uromodulin is a key molecule underlying the mechanisms or therapeutic approaches of chronic kidney disease, particularly nephrosclerosis and diabetic nephropathy, which are causes of end-stage renal disease. This review focuses on the current understanding of the role of uromodulin from a biological, physiological, and pathological standpoint.

Unveiling the Hidden Power of Uromodulin: A Promising Potential Biomarker for Kidney Diseases

Uromodulin, also known as Tamm-Horsfall protein, represents the predominant urinary protein in healthy individuals. Over the years, studies have revealed compelling associations between urinary and serum concentrations of uromodulin and various parameters, encompassing kidney function, graft survival, cardiovascular disease, glucose metabolism, and overall mortality. Consequently, there has been a growing interest in uromodulin as a novel and effective biomarker with potential applications in diverse clinical settings. Reduced urinary uromodulin levels have been linked to an elevated risk of acute kidney injury (AKI) following cardiac surgery. In the context of chronic kidney disease (CKD) of different etiologies, urinary uromodulin levels tend to decrease significantly and are strongly correlated with variations in estimated glomerular filtration rate. The presence of uromodulin in the serum, attributable to basolateral epithelial cell leakage in the thick ascending limb, has been observed. This serum uromodulin level is closely associated with kidney function and histological severity, suggesting its potential as a biomarker capable of reflecting disease severity across a spectrum of kidney disorders. The UMOD gene has emerged as a prominent locus linked to kidney function parameters and CKD risk within the general population. Extensive research in multiple disciplines has underscored the biological significance of the top UMOD gene variants, which have also been associated with hypertension and kidney stones, thus highlighting the diverse and significant impact of uromodulin on kidney-related conditions. UMOD gene mutations are implicated in uromodulin-associated kidney disease, while polymorphisms in the UMOD gene show a significant association with CKD. In conclusion, uromodulin holds great promise as an informative biomarker, providing valuable insights into kidney function and disease progression in various clinical scenarios. The identification of UMOD gene variants further strengthens its relevance as a potential target for better understanding kidney-related pathologies and devising novel therapeutic strategies. Future investigations into the roles of uromodulin and regulatory mechanisms are likely to yield even more profound implications for kidney disease diagnosis, risk assessment, and management.

Dnajb11-Kidney Disease Develops from Reduced Polycystin-1 Dosage but not Unfolded Protein Response in Mice

SIGNIFICANCE STATEMENT

Heterozygous DNAJB11 mutation carriers manifest with small cystic kidneys and renal failure in adulthood. Recessive cases with prenatal cystic kidney dysplasia were recently described. Our in vitro and mouse model studies investigate the proposed disease mechanism as an overlap of autosomal-dominant polycystic kidney disease and autosomal-dominant tubulointerstitial kidney disease pathogenesis. We find that DNAJB11 loss impairs cleavage and maturation of the autosomal-dominant polycystic kidney disease protein polycystin-1 (PC1) and results in dosage-dependent cyst formation in mice. We find that Dnajb11 loss does not activate the unfolded protein response, drawing a fundamental contrast with the pathogenesis of autosomal-dominant tubulointerstitial kidney disease. We instead propose that fibrosis in DNAJB11 -kidney disease may represent an exaggerated response to polycystin-dependent cysts.

BACKGROUND

Patients with heterozygous inactivating mutations in DNAJB11 manifest with cystic but not enlarged kidneys and renal failure in adulthood. Pathogenesis is proposed to resemble an overlap of autosomal-dominant polycystic kidney disease (ADPKD) and autosomal-dominant tubulointerstitial kidney disease (ADTKD), but this phenotype has never been modeled in vivo . DNAJB11 encodes an Hsp40 cochaperone in the endoplasmic reticulum: the site of maturation of the ADPKD polycystin-1 (PC1) protein and of unfolded protein response (UPR) activation in ADTKD. We hypothesized that investigation of DNAJB11 would shed light on mechanisms for both diseases.

METHODS

We used germline and conditional alleles to model Dnajb11 -kidney disease in mice. In complementary experiments, we generated two novel Dnajb11-/- cell lines that allow assessment of PC1 C-terminal fragment and its ratio to the immature full-length protein.

RESULTS

Dnajb11 loss results in a profound defect in PC1 cleavage but with no effect on other cystoproteins assayed. Dnajb11-/- mice are live-born at below the expected Mendelian ratio and die at a weaning age with cystic kidneys. Conditional loss of Dnajb11 in renal tubular epithelium results in PC1 dosage-dependent kidney cysts, thus defining a shared mechanism with ADPKD. Dnajb11 mouse models show no evidence of UPR activation or cyst-independent fibrosis, which is a fundamental distinction from typical ADTKD pathogenesis.

CONCLUSIONS

DNAJB11 -kidney disease is on the spectrum of ADPKD phenotypes with a PC1-dependent pathomechanism. The absence of UPR across multiple models suggests that alternative mechanisms, which may be cyst-dependent, explain the renal failure in the absence of kidney enlargement.

Identifying Genetic Variants and Metabolites Associated with Rapid Estimated Glomerular Filtration Rate Decline in Korea Based on Genome-Metabolomic Integrative Analysis

Identifying the predisposing factors to chronic or end-stage kidney disease is essential to preventing or slowing kidney function decline. Therefore, here, we investigated the genetic variants related to a rapid decline in the estimated glomerular filtration rate (eGFR) (i.e., a loss of >5 mL/min/1.73 m2 per year) and verified the relationships between variant-related diseases and metabolic pathway signaling in patients with chronic kidney disease. We conducted a genome-wide association study that included participants with diabetes, hypertension, and rapid eGFR decline from two Korean data sources (N = 115 and 69 for the discovery and the validation cohorts, respectively). We identified a novel susceptibility locus: 4q32.3 (rs10009742 in the MARCHF1 gene, beta = −3.540, P = 4.11 × 10−8). Fine-mapping revealed 19 credible, causal single-nucleotide polymorphisms, including rs10009742. The pimelylcarnitine and octadecenoyl carnitine serum concentrations were associated with rs10009742 (beta = 0.030, P = 7.10 × 10−5, false discovery rate (FDR) = 0.01; beta = 0.167, P = 8.11 × 10−4, FDR = 0.08). Our results suggest that MARCHF1 is associated with a rapid eGFR decline in patients with hypertension and diabetes. Furthermore, MARCHF1 affects the pimelylcarnitine metabolite concentration, which may mediate chronic kidney disease progression by inducing oxidative stress in the endoplasmic reticulum.

Upregulation of C/EBP Homologous Protein induced by ER Stress Mediates Epithelial to Myofibroblast Transformation in ADTKD-UMOD

Autosomal dominant tubulointerstitial kidney disease due to UMOD mutations (ADTKD-UMOD) results in chronic interstitial nephritis, which gradually develops into end-stage renal disease. It is believed that the accumulation of mutant uromodulin causes the endoplasmic reticulum (ER) stress, then leads to the kidney damage. But the underlying mechanism remains unclear. To find the ADTKD-UMOD patients, UMOD gene screening was performed in 26 patients with unexplained chronic interstitial nephritis, during the past 10 years in our department, and among them three ADTKD-UMOD cases were discovered. Routine pathological staining and electron microscopy sections were reviewed again to confirm their kidney lesions. Immunostaining of UMOD and ER stress marker GRP78, as well as CHOP have all been done. The strong colocalization of UMOD with GRP78 and CHOP in ADTKD-UMOD patients but not in other chronic interstitial nephritis patients had been found. Moreover in vitro experiments, ER stress induced by tunicamycin (TM) not only significantly increased the expression of GRP78 and CHOP, but also caused the epithelial to myofibroblast transformation (EMT) of renal tubular epithelial cells, evidenced by decreased expression of E-cadherin and increased expression of vimentin, and extracellular matrix (ECM) deposition, evidenced by increased expression of fibronectin (FN). CHOP knockdown could restore the upregulation of vimentin and FN induced by TM. Thus, specific activation of CHOP in renal tubular epithelial cells induced by UMOD protein might be the key reason of renal interstitial fibrosis in ADTKD-UMOD patients.

Clinical and genetic spectra of autosomal dominant tubulointerstitial kidney disease

Autosomal dominant tubulointerstitial kidney disease (ADTKD) is a clinical entity defined by interstitial fibrosis with tubular damage, bland urinalysis and progressive kidney disease. Mutations in UMOD and MUC1 are the most common causes of ADTKD but other rarer (REN, SEC61A1), atypical (DNAJB11) or heterogeneous (HNF1B) subtypes have been described. Raised awareness, as well as the implementation of next-generation sequencing approaches, have led to a sharp increase in reported cases. ADTKD is now believed to be one of the most common monogenic forms of kidney disease and overall it probably accounts for ∼5% of all monogenic causes of chronic kidney disease. Through international efforts and systematic analyses of patient cohorts, critical insights into clinical and genetic spectra of ADTKD, genotype-phenotype correlations as well as innovative diagnostic approaches have been amassed during recent years. In addition, intense research efforts are addressed towards deciphering and rescuing the cellular pathways activated in ADTKD. A better understanding of these diseases and of possible commonalities with more common causes of kidney disease may be relevant to understand and target mechanisms leading to fibrotic kidney disease in general. Here we highlight recent advances in our understanding of the different subtypes of ADTKD with an emphasis on the molecular underpinnings and its clinical presentations.

The impact of intradialytic exercise on immune cells expressing CCR5+ in patients with chronic kidney disease: A cross-over trial

The C-C chemokine receptor type 5 (CCR5) plays a role in the immunopathogenesis of chronic kidney disease (CKD). Exercise has anti-inflammatory properties that may contribute to the rehabilitation of CKD patients. To date, the impact of the intradialytic exercise on CCR5 expression in monocytes and lymphocytes of CKD patients is unknown. We aimed to evaluate the effects of an acute intradialytic moderate-intensity exercise on CD4+CCR5+ T-cells and CD14+CCR5+ monocytes of elderly individuals with Chronic Kidney Disease (CKD). Eight CKD elderly patients performed a single bout of 20 min intradialytic exercise and a control hemodialysis (HD) session. Blood samples were collected at baseline, during and immediately after the trials. HD therapy increased the peripheral frequency of CD4+CCR5+ T-cells. The systemic CCL5 levels and the peripheral CD14+CCR5+ proportions increased during and after HD therapy. No significant alterations in CD4+CCR5+ and CD14+CCR5+ proportions or CCL5 levels were identified in CKD patients during and after intradialytic exercise. A negative correlation between the peripheral frequency of CD14+CCR5+ and the creatinine levels was identified in the intradialytic exercise session. A single moderate-intensity intradialytic exercise imposes an immunomodulatory impact in CKD elderly patients, preventing an excessive inflammatory response induced by hemodialysis.

Uromodulin: Roles in Health and Disease

Uromodulin, a protein exclusively produced by the kidney, is the most abundant urinary protein in physiological conditions. Already described several decades ago, uromodulin has gained the spotlight in recent years, since the discovery that mutations in its encoding gene UMOD cause a renal Mendelian disease (autosomal dominant tubulointerstitial kidney disease) and that common polymorphisms are associated with multifactorial disorders, such as chronic kidney disease, hypertension, and cardiovascular diseases. Moreover, variations in uromodulin levels in urine and/or blood reflect kidney functioning mass and are of prognostic value for renal function, cardiovascular events, and overall mortality. The clinical relevance of uromodulin reflects its multifunctional nature, playing a role in renal ion transport and immunomodulation, in protection against urinary tract infections and renal stones, and possibly as a systemic antioxidant. Here, we discuss the multifaceted roles of this protein in kidney physiology and its translational relevance.

A Rare Kidney Disease To Cure Them All? Towards Mechanism-Based Therapies for Proteinopathies

Autosomal dominant tubulointerstitial kidney diseases (ADTKDs) are a group of rare genetic diseases that lead to kidney failure. Mutations in the MUC1 gene cause ADTKD-MUC1 (MUC1 kidney disease, MKD), a disorder with no available therapies. Recent studies have identified the molecular and cellular mechanisms that drive MKD disease pathogenesis. Armed with patient-derived cell lines and pluripotent stem cell (iPSC)-derived kidney organoids, it was found that MKD is a toxic proteinopathy caused by the intracellular accumulation of misfolded MUC1 protein in the early secretory pathway. We discuss the advantages of studying rare monogenic kidney diseases, describe effective patient-derived model systems, and highlight recent mechanistic insights into protein quality control that have implications for additional proteinopathies beyond rare kidney diseases.

Comprehensive assessment of side effects in COVID-19 drug pipeline from a network perspective

Currently, coronavirus disease 2019 (COVID-19), has posed an imminent threat to global public health. Although some current therapeutic agents have showed potential prevention or treatment, a growing number of associated adverse events have occurred on patients with COVID-19 in the course of medical treatment. Therefore, a comprehensive assessment of the safety profile of therapeutic agents against COVID-19 is urgently needed. In this study, we proposed a network-based framework to identify the potential side effects of current COVID-19 drugs in clinical trials. We established the associations between 116 COVID-19 drugs and 30 kinds of human tissues based on network proximity and gene-set enrichment analysis (GSEA) approaches. Additionally, we focused on four types of drug-induced toxicities targeting four tissues, including hepatotoxicity, renal toxicity, lung toxicity, and neurotoxicity, and validated our network-based predictions by preclinical and clinical evidence available. Finally, we further performed pharmacovigilance analysis to validate several drug-tissue toxicities via data mining adverse event reporting data, and we identified several new drug-induced side effects without labeling in Food and Drug Administration (FDA) drug instructions. Overall, this study provides forceful approaches to assess potential side effects on COVID-19 drugs, which will be helpful for their safe use in clinical practice and promoting the discovery of antiviral therapeutics against SARS-CoV-2.

A Uromodulin Mutation Drives Autoimmunity and Kidney Mononuclear Phagocyte Endoplasmic Reticulum Stress

We identified a family with a UMOD gene mutation (C106F) resulting in glomerular inflammation and complement deposition. To determine if the observed phenotype is due to immune system activation by mutant uromodulin, a mouse strain with a homologous cysteine to phenylalanine mutation (C105F) in the UMOD gene was generated using CRISPR-Cas9 gene editing and the effect of this mutation on mononuclear phagocytic cells was examined. Mutant mice developed high levels of intracellular and secreted aggregated uromodulin, resulting in anti-uromodulin antibodies and circulating uromodulin containing immune complexes with glomerular deposition and kidney fibrosis with aging. F4/80⁺ and CD11c⁺ kidney cells phagocytize uromodulin. Differential gene expression analysis by RNA sequencing of F4/80⁺ phagocytic cells revealed activation of the activating transcription factor 5 (ATF5)-mediated stress response pathway in mutant mice. Phagocytosis of mutant uromodulin by cultured dendritic cells resulted in activation of the endoplasmic reticulum stress response pathway and markers of cell inactivation, an effect not seen with wild-type protein. Mutant mice demonstrate a twofold increase in T-regulatory cells, consistent with induction of immune tolerance, resulting in decreased inflammatory response and improved tissue repair following ischemia-reperfusion injury. The C105F mutation results in autoantibodies against aggregated misfolded protein with immune complex formation and kidney fibrosis. Aggregated uromodulin may induce dendritic cell tolerance following phagocytosis through an unfolded protein/endoplasmic reticulum stress response pathway, resulting in decreased inflammation following tissue injury.

Autosomal dominant tubulointerstitial kidney disease: a new tool to guide genetic testing

Autosomal dominant tubulointerstitial disease (ADTKD) is a dominantly inherited progressive nonglomerular disease. Several factors, such as a nonspecific clinical presentation and relative rarity, impede the phenotyping of ADTKD into clinically relevant subtypes and impair the appropriate implementation of genetic testing. The study by Olinger et al. describes the largest multicenter ADTKD cohort, which is likely to become a key resource. The authors also provide a new clinical tool that could guide diagnosis and genetic testing.

Clinical and genetic spectra of autosomal dominant tubulointerstitial kidney disease due to mutations in UMOD and MUC1

Autosomal dominant tubulointerstitial kidney disease (ADTKD) is an increasingly recognized cause of end-stage kidney disease, primarily due to mutations in UMOD and MUC1. The lack of clinical recognition and the small size of cohorts have slowed the understanding of disease ontology and development of diagnostic algorithms. We analyzed two registries from Europe and the United States to define genetic and clinical characteristics of ADTKD-UMOD and ADTKD-MUC1 and develop a practical score to guide genetic testing. Our study encompassed 726 patients from 585 families with a presumptive diagnosis of ADTKD along with clinical, biochemical, genetic and radiologic data. Collectively, 106 different UMOD mutations were detected in 216/562 (38.4%) of families with ADTKD (303 patients), and 4 different MUC1 mutations in 72/205 (35.1%) of the families that are UMOD-negative (83 patients). The median kidney survival was significantly shorter in patients with ADTKD-MUC1 compared to ADTKD-UMOD (46 vs. 54 years, respectively), whereas the median gout-free survival was dramatically reduced in patients with ADTKD-UMOD compared to ADTKD-MUC1 (30 vs. 67 years, respectively). In contrast to patients with ADTKD-UMOD, patients with ADTKD-MUC1 had normal urinary excretion of uromodulin and distribution of uromodulin in tubular cells. A diagnostic algorithm based on a simple score coupled with urinary uromodulin measurements separated patients with ADTKD-UMOD from those with ADTKD-MUC1 with a sensitivity of 94.1%, a specificity of 74.3% and a positive predictive value of 84.2% for a UMOD mutation. Thus, ADTKD-UMOD is more frequently diagnosed than ADTKD-MUC1, ADTKD subtypes present with distinct clinical features, and a simple score coupled with urine uromodulin measurements may help prioritizing genetic testing.

Uromodulin in mineral metabolism

PURPOSE OF REVIEW

Uromodulin (UMOD), also known as Tamm-Horsfall protein, is the most abundant protein in human urine. UMOD has multiple functions such as protection against urinary tract infections and nephrolithiasis. This review outlines recent progress made in UMOD's role in renal physiology, tubular transport, and mineral metabolism.

RECENT FINDINGS

UMOD is mostly secreted in the thick ascending limb (TAL) and to a lesser degree in the distal convoluted tubule (DCT). UMOD secretion is regulated by the calcium-sensing receptor. UMOD upregulates ion channels [e.g., renal outer medullary potassium channel, transient receptor potential cation channel subfamily V member 5, and transient receptor potential melastatin 6 (TRPM6)] and cotransporters [e.g., Na,K,2Cl cotransporter (NKCC2) and sodium-chloride cotransporter (NCC)] in the TAL and DCT. Higher serum UMOD concentrations have been associated with higher renal function and preserved renal reserve. Higher serum UMOD has also been linked to a lower risk of cardiovascular disease and diabetes mellitus.

SUMMARY

With better serum UMOD detection assays the extent of different functions for UMOD is still expanding. Urinary UMOD regulates different tubular ion channels and cotransporters. Variations of urinary UMOD secretion can so contribute to common disorders such as hypertension or nephrolithiasis.

Autosomal dominant tubulointerstitial kidney disease

Autosomal dominant tubulointerstitial kidney disease (ADTKD) is a recently defined entity that includes rare kidney diseases characterized by tubular damage and interstitial fibrosis in the absence of glomerular lesions, with inescapable progression to end-stage renal disease. These diseases have long been neglected and under-recognized, in part due to confusing and inconsistent terminology. The introduction of a gene-based, unifying terminology led to the identification of an increasing number of cases, with recent data suggesting that ADTKD is one of the more common monogenic kidney diseases after autosomal dominant polycystic kidney disease, accounting for ~5% of monogenic disorders causing chronic kidney disease. ADTKD is caused by mutations in at least five different genes, including UMOD, MUC1, REN, HNF1B and, more rarely, SEC61A1. These genes encode various proteins with renal and extra-renal functions. The mundane clinical characteristics and lack of appreciation of family history often result in a failure to diagnose ADTKD. This Primer highlights the different types of ADTKD and discusses the distinct genetic and clinical features as well as the underlying mechanisms.

Autosomal Dominant Tubulointerstitial Kidney Disease with Adult Onset due to a Novel Renin Mutation Mapping in the Mature Protein

Autosomal dominant tubulointerstitial kidney disease (ADTKD) is a genetically heterogeneous renal disorder leading to progressive loss of renal function. ADTKD-REN is due to rare mutations in renin, all localized in the protein leader peptide and affecting its co-translational insertion in the endoplasmic reticulum (ER). Through exome sequencing in an adult-onset ADTKD family we identified a new renin variant, p.L381P, mapping in the mature protein. To assess its pathogenicity, we combined genetic data, computational and predictive analysis and functional studies. The L381P substitution affects an evolutionary conserved residue, co-segregates with renal disease, is not found in population databases and is predicted to be deleterious by in silico tools and by structural modelling. Expression of the L381P variant leads to its ER retention and induction of the Unfolded Protein Response in cell models and to defective pronephros development in zebrafish. Our work shows that REN mutations outside of renin leader peptide can cause ADTKD and delineates an adult form of ADTKD-REN, a condition which has usually its onset in childhood. This has implications for the molecular diagnosis and the estimated prevalence of the disease and points at ER homeostasis as a common pathway affected in ADTKD-REN, and possibly more generally in ADTKD.

UMOD gene mutations in Chinese patients with autosomal dominant tubulointerstitial kidney disease: a pediatric case report and literature review

Background

Autosomal dominant tubulointerstitial kidney disease (ADTKD) caused by UMOD gene mutation (ADTKD-UMOD) is rare in children, characterized by hyperuricemia, gout, and progressive chronic kidney disease. It usually leads to end-stage renal failure at fiftieth decades. Here, we report a 3-year-old Chinese boy in an ADTKD family caused by a novel UMOD gene mutation.

Case presentation

A 3-year-old boy was admitted to our hospital because of persistent hematuria. Urinalysis showed BLD 2+ without proteinuria. The serum levels of uric acid, creatinine and electrolytes were normal. No renal cyst or calculus was found by ultrasonography. Renal biopsy was performed and focal and segmental glomerulosclerosis was found in 4 glomeruli among 35 glomeruli examined. His father was found with end-stage renal disease (ESRD) at the age of 29, and renal ultrasound showed several cysts in both kidneys. A novel heterozygous mutation (c.1648G > A,p.V550I) in exon 8 of UMOD gene was identified by whole exome sequencing in the family. SCBC Genome Browser alignment showed that V550 were highly conserved in uromodulin among different species. Software predicted that the mutation is suspected to be harmful. By literature review, there are 12 mutations of UMOD gene in 14 Chinese families including only one pediatric case(a 16-year-old girl).

Conclusions

A novel heterozygous mutation (c.1648G > A,p.V550I) in exon 8 of UMOD gene was found in in a Chinese child case with ADTKD-UMOD, which extends our understanding of UMOD gene mutation spectrum and phenotype of ADTKD-UMOD in children.

Functional Urate-Associated Genetic Variants Influence Expression of lincRNAs LINC01229 and MAFTRR

Genetic variation in the genomic regulatory landscape likely plays a crucial role in the pathology of disease. Non-coding variants associated with disease can influence the expression of long intergenic non-coding RNAs (lincRNAs), which in turn function in the control of protein-coding gene expression. Here, we investigate the function of two independent serum urate-associated signals (SUA1 and SUA2) in close proximity to lincRNAs and an enhancer that reside ∼60 kb and ∼300 kb upstream of MAF, respectively. Variants within SUA1 are expression quantitative trait loci (eQTL) for LINC01229 and MAFTRR, both co-expressed with MAF. We have also identified that variants within SUA1 are trans-eQTL for genes that are active in kidney- and serum urate-relevant pathways. Serum urate-associated variants rs4077450 and rs4077451 within SUA2 lie within an enhancer that recruits the transcription factor HNF4α and forms long range interactions with LINC01229 and MAFTRR. The urate-raising alleles of rs4077450 and rs4077451 increase enhancer activity and associate with increased expression of LINC01229. We show that the SUA2 enhancer region drives expression in the zebrafish pronephros, recapitulating endogenous MAF expression. Depletion of MAFTRR and LINC01229 in HEK293 cells in turn lead to increased MAF expression. Collectively, our results are consistent with serum urate variants mediating long-range transcriptional regulation of the lincRNAs LINC01229 and MAFTRR and urate relevant genes (e.g., SLC5A8 and EHHADH) in trans.

Uromodulin-related autosomal-dominant tubulointerstitial kidney disease-pathogenetic insights based on a case

Uromodulin-related autosomal-dominant tubulointerstitial kidney disease (ADTKD-UMOD) is a rare monogenic disorder that is characterized by tubulointerstitial fibrosis and progression of kidney function loss, and may progress to end-stage renal disease. It is usually accompanied by hyperuricaemia and gout. Mutations in the uromodulin gene (UMOD) resulting in malfunctioning of UMOD are known to be the cause of ADTKD-UMOD, which is assumed to be an endoplasmatic reticulum (ER) storage disease. As a case vignette, we report a 29-year-old female with a suspicious family history of chronic kidney disease presenting with progressive loss of renal function, hyperuricaemia and frequent urinary tract infections. Urinary tract infections and pyelonephritides may represent a clinical feature of uromodulin malfunction as it plays a protective role against urinary tract infections despite only sporadic data on this topic. ADTKD-UMOD was diagnosed after genetic testing revealing a missense mutation in the UMOD gene. Light microscopy showed excessive tubular interstitial fibrosis and tubular atrophy together with signs of glomerular sclerosis. Electron microscopic findings could identify electron dense storage deposits in the ER of tubular epithelial cells of the thick ascending loop. Immunohistological staining with KDEL (lysine, aspartic acid, glutamic acid, leucine) showed positivity in the tubular cells, which likely represents ER expansion upon accumulation of misfolded UMOD which could trigger the unfolded protein response and ER stress. This review highlights pathophysiological mechanisms that are subject to ADTKD-UMOD.

Regulation of IRE1 RNase activity by the Ribonuclease inhibitor 1 (RNH1)

Adaptation to endoplasmic reticulum (ER) stress depends on the activation of the sensor inositol-requiring enzyme 1α (IRE1), an endoribonuclease that splices the mRNA of the transcription factor XBP1 (X-box-binding protein 1). To better understand the protein network that regulates the activity of the IRE1 pathway, we systematically screened the proteins that interact with IRE1 and identified a ribonuclease inhibitor called ribonuclease/angiogenin inhibitor 1 (RNH1). RNH1 is a leucine-rich repeat domains-containing protein that binds to and inhibits ribonucleases. Immunoprecipitation experiments confirmed this interaction. Docking experiments indicated that RNH1 physically interacts with IRE1 through its cytosolic RNase domain. Upon ER stress, the interaction of RNH1 with IRE1 in the ER increased at the expense of the nuclear pool of RNH1. Inhibition of RNH1 expression using siRNA mediated RNA interference upon ER stress led to an increased splicing activity of XBP1. Modulation of IRE1 RNase activity by RNH1 was recapitulated in a cell-free system, suggesting direct regulation of IRE1 by RNH. We conclude that RNH1 attenuates the activity of IRE1 by interacting with its ribonuclease domain. These findings have implications for understanding the molecular mechanism by which IRE1 signaling is attenuated upon ER stress.

The Expanding Therapeutic Perspective of CCR5 Blockade

CCR5 and its interaction with chemokine ligands have been crucial for understanding and tackling HIV-1 entry into target cells. However, over time, CCR5 has witnessed an impressive transition from being considered rather unimportant in physiology and pathology to becoming central in a growing number of pathophysiological conditions. It now turns out that the massive efforts devoted to combat HIV-1 entry by interfering with CCR5, and the subsequent production of chemokine ligand variants, small chemical compounds, and other molecular entities and strategies, may set the therapeutic standards for a wealth of different pathologies. Expressed on various cell types, CCR5 plays a vital role in the inflammatory response by directing cells to sites of inflammation. Aside HIV-1, CCR5 has been implicated in other infectious diseases and non-infectious diseases such as cancer, atherosclerosis, and inflammatory bowel disease. Individuals carrying the CCR5Δ32 mutation live a normal life and are warranted a natural barrier to HIV-1 infection. Therefore, CCR5 antagonism and gene-edited knockout of the receptor gained growing interest for the therapeutic role that CCR5 blockade may play in the attenuation of the severity or progression of numerous diseases.