Copy Number Variant Analysis and Genome-wide Association Study Identify Loci with Large Effect for Vesicoureteral Reflux.

BACKGROUND: Vesicoureteral reflux (VUR) is a common, familial genitourinary disorder, and a major cause of pediatric urinary tract infection (UTI) and kidney failure. The genetic basis of VUR is not well understood. METHODS: A diagnostic analysis sought rare, pathogenic copy number variant (CNV) disorders among 1737 patients with VUR. A GWAS was performed in 1395 patients and 5366 controls, of European ancestry. RESULTS: Altogether, 3% of VUR patients harbored an undiagnosed rare CNV disorder, such as the 1q21.1, 16p11.2, 22q11.21, and triple X syndromes ((OR, 3.12; 95% CI, 2.10 to 4.54; P=6.35×10-8) The GWAS identified three study-wide significant and five suggestive loci with large effects (ORs, 1.41-6.9), containing canonical developmental genes expressed in the developing urinary tract (WDPCP, OTX1, BMP5, VANGL1, and WNT5A). In particular, 3.3% of VUR patients were homozygous for an intronic variant in WDPCP (rs13013890; OR, 3.65; 95% CI, 2.39 to 5.56; P=1.86×10-9). This locus was associated with multiple genitourinary phenotypes in the UK Biobank and eMERGE studies. Analysis of Wnt5a mutant mice confirmed the role of Wnt5a signaling in bladder and ureteric morphogenesis. CONCLUSIONS: These data demonstrate the genetic heterogeneity of VUR. Altogether, 6% of patients with VUR harbored a rare CNV or a common variant genotype conferring an OR >3. Identification of these genetic risk factors has multiple implications for clinical care and for analysis of outcomes in VUR.

Exome-wide Association Study Identifies GREB1L Mutations in Congenital Kidney Malformations.

Renal agenesis and hypodysplasia (RHD) are major causes of pediatric chronic kidney disease and are highly genetically heterogeneous. We conducted whole-exome sequencing in 202 case subjects with RHD and identified diagnostic mutations in genes known to be associated with RHD in 7/202 case subjects. In an additional affected individual with RHD and a congenital heart defect, we found a homozygous loss-of-function (LOF) variant in SLIT3, recapitulating phenotypes reported with Slit3 inactivation in the mouse. To identify genes associated with RHD, we performed an exome-wide association study with 195 unresolved case subjects and 6,905 control subjects. The top signal resided in GREB1L, a gene implicated previously in Hoxb1 and Shha signaling in zebrafish. The significance of the association, which was p = 2.0 × 10-5 for novel LOF, increased to p = 4.1 × 10-6 for LOF and deleterious missense variants combined, and augmented further after accounting for segregation and de novo inheritance of rare variants (joint p = 2.3 × 10-7). Finally, CRISPR/Cas9 disruption or knockdown of greb1l in zebrafish caused specific pronephric defects, which were rescued by wild-type human GREB1L mRNA, but not mRNA containing alleles identified in case subjects. Together, our study provides insight into the genetic landscape of kidney malformations in humans, presents multiple candidates, and identifies SLIT3 and GREB1L as genes implicated in the pathogenesis of RHD.

Mutations in DSTYK and dominant urinary tract malformations.

BACKGROUND: Congenital abnormalities of the kidney and the urinary tract are the most common cause of pediatric kidney failure. These disorders are highly heterogeneous, and the etiologic factors are poorly understood. METHODS: We performed genomewide linkage analysis and whole-exome sequencing in a family with an autosomal dominant form of congenital abnormalities of the kidney or urinary tract (seven affected family members). We also performed a sequence analysis in 311 unrelated patients, as well as histologic and functional studies. RESULTS: Linkage analysis identified five regions of the genome that were shared among all affected family members. Exome sequencing identified a single, rare, deleterious variant within these linkage intervals, a heterozygous splice-site mutation in the dual serine-threonine and tyrosine protein kinase gene (DSTYK). This variant, which resulted in aberrant splicing of messenger RNA, was present in all affected family members. Additional, independent DSTYK mutations, including nonsense and splice-site mutations, were detected in 7 of 311 unrelated patients. DSTYK is highly expressed in the maturing epithelia of all major organs, localizing to cell membranes. Knockdown in zebrafish resulted in developmental defects in multiple organs, which suggested loss of fibroblast growth factor (FGF) signaling. Consistent with this finding is the observation that DSTYK colocalizes with FGF receptors in the ureteric bud and metanephric mesenchyme. DSTYK knockdown in human embryonic kidney cells inhibited FGF-stimulated phosphorylation of extracellular-signal-regulated kinase (ERK), the principal signal downstream of receptor tyrosine kinases. CONCLUSIONS: We detected independent DSTYK mutations in 2.3% of patients with congenital abnormalities of the kidney or urinary tract, a finding that suggests that DSTYK is a major determinant of human urinary tract development, downstream of FGF signaling. (Funded by the National Institutes of Health and others.).

Glomerular Autoimmune Multicomponents of Human Lupus Nephritis In Vivo (2): Planted Antigens.

Glomerular planted antigens (histones, DNA, and C1q) are potential targets of autoimmunity in lupus nephritis (LN). However, the characterization of these antigens in human glomeruli in vivo remains inconsistent. We eluted glomerular autoantibodies recognizing planted antigens from laser-microdissected renal biopsy samples of 20 patients with LN. Prevalent antibody isotypes were defined, levels were determined, and glomerular colocalization was investigated. Renal and circulating antibodies were matched, and serum levels were compared in 104 patients with LN, 84 patients with SLE without LN, and 50 patients with rheumatoid arthritis (RA). Autoantibodies against podocyte antigens (anti-α-enolase/antiannexin AI) were also investigated. IgG2 autoantibodies against DNA, histones (H2A, H3, and H4), and C1q were detected in 50%, 55%, and 70% of biopsy samples, respectively. Anti-DNA IgG3 was the unique non-IgG2 anti-DNA deposit, and anti-C1q IgG4 was mainly detected in subepithelial membranous deposits. Anti-H3, anti-DNA, and anti-C1q IgG2 autoantibodies were also prevalent in LN serum, which also contained IgG3 against the antigen panel and anti-C1q IgG4. Serum and glomerular levels of autoantibodies were not strictly associated. High serum levels of all autoantibodies detected, including anti-α-enolase and antiannexin AI, identified LN versus SLE and RA. Anti-H3 and anti-α-enolase IgG2 levels had the most remarkable increase in LN serum and represented a discriminating feature of LN in principal component analysis. The highest levels of these two autoantibodies were also associated with proteinuria>3.5 g/24 hours and creatinine>1.2 mg/dl. Our findings suggest that timely autoantibody characterization might allow outcome prediction and targeted therapies for patients with nephritis.

Copy-number disorders are a common cause of congenital kidney malformations.

We examined the burden of large, rare, copy-number variants (CNVs) in 192 individuals with renal hypodysplasia (RHD) and replicated findings in 330 RHD cases from two independent cohorts. CNV distribution was significantly skewed toward larger gene-disrupting events in RHD cases compared to 4,733 ethnicity-matched controls (p = 4.8 × 10(-11)). This excess was attributable to known and novel (i.e., not present in any database or in the literature) genomic disorders. All together, 55/522 (10.5%) RHD cases harbored 34 distinct known genomic disorders, which were detected in only 0.2% of 13,839 population controls (p = 1.2 × 10(-58)). Another 32 (6.1%) RHD cases harbored large gene-disrupting CNVs that were absent from or extremely rare in the 13,839 population controls, identifying 38 potential novel or rare genomic disorders for this trait. Deletions at the HNF1B locus and the DiGeorge/velocardiofacial locus were most frequent. However, the majority of disorders were detected in a single individual. Genomic disorders were detected in 22.5% of individuals with multiple malformations and 14.5% of individuals with isolated urinary-tract defects; 14 individuals harbored two or more diagnostic or rare CNVs. Strikingly, the majority of the known CNV disorders detected in the RHD cohort have previous associations with developmental delay or neuropsychiatric diseases. Up to 16.6% of individuals with kidney malformations had a molecular diagnosis attributable to a copy-number disorder, suggesting kidney malformations as a sentinel manifestation of pathogenic genomic imbalances. A search for pathogenic CNVs should be considered in this population for the diagnosis of their specific genomic disorders and for the evaluation of the potential for developmental delay.

Glomerular autoimmune multicomponents of human lupus nephritis in vivo: α-enolase and annexin AI.

Renal targets of autoimmunity in human lupus nephritis (LN) are unknown. We sought to identify autoantibodies and glomerular target antigens in renal biopsy samples from patients with LN and determine whether the same autoantibodies can be detected in circulation. Glomeruli were microdissected from biopsy samples of 20 patients with LN and characterized by proteomic techniques. Serum samples from large cohorts of patients with systemic lupus erythematosus (SLE) with and without LN and other glomerulonephritides were tested. Glomerular IgGs recognized 11 podocyte antigens, with reactivity varying by LN pathology. Notably, IgG2 autoantibodies against α-enolase and annexin AI were detected in 11 and 10 of the biopsy samples, respectively, and predominated over other autoantibodies. Immunohistochemistry revealed colocalization of α-enolase or annexin AI with IgG2 in glomeruli. High levels of serum anti-α-enolase (>15 mg/L) IgG2 and/or anti-annexin AI (>2.7 mg/L) IgG2 were detected in most patients with LN but not patients with other glomerulonephritides, and they identified two cohorts: patients with high anti-α-enolase/low anti-annexin AI IgG2 and patients with low anti-α-enolase/high anti-annexin AI IgG2. Serum levels of both autoantibodies decreased significantly after 12 months of therapy for LN. Anti-α-enolase IgG2 recognized specific epitopes of α-enolase and did not cross-react with dsDNA. Furthermore, nephritogenic monoclonal IgG2 (clone H147) derived from lupus-prone MRL-lpr/lpr mice recognized human α-enolase, suggesting homology between animal models and human LN. These data show a multiantibody composition in LN, where IgG2 autoantibodies against α-enolase and annexin AI predominate in the glomerulus and can be detected in serum.

Atypical haemolytic uraemic syndrome with underlying glomerulopathies. A case series and a review of the literature.

BACKGROUND: Primary or secondary glomerulonephritis has been anecdotally reported in association with atypical haemolytic uraemic syndrome (aHUS). We here report a series of six patients who developed aHUS and glomerulopathy, and review the literature on aHUS and glomerulonephritis. METHODS: Out of all patients diagnosed at our unit with biopsy-proven glomerular diseases between March 2007 and October 2011, selected cases developing aHUS during the follow-up are presented. The following tests were performed in all six patients: serum C3 and C4 levels, ADAMTS13 activity, CFH levels and anti-CFH autoantibodies and genetic screening for CFH, MCP, CFI, C3 and CFHR1-3 mutations and risk haplotypes associated with aHUS. RESULTS: Two hundred and forty-eight patients received a biopsy-proven diagnosis of glomerulopathy and were followed for a median of 31 months (range 2-58). Of these, six developed aHUS, within a median of 15 months (range 1-36) of their initial diagnosis of glomerulopathy. One of these patients had focal segmental glomerulosclerosis (FSGS), two membranoproliferative glomerulonephritis (MPGN) type I, one C3 glomerulonephritis and two systemic small vessel vasculitis [one granulomatosis with polyangiitis (Wegener's), one Henoch-Schoenlein purpura]. Five patients (one of them heterozygous for a CFH mutation) carried, in homo- or heterozygosity, the risk haplotype CFH-H3 (CFH tgtgt), previously described to be associated with aHUS, while another one patient was homozygous for the MCPggaac risk haplotype predisposing to aHUS when present on both alleles. CONCLUSIONS: Different types of glomerulopathies can be complicated by aHUS. Several mechanisms can contribute to this association, such as nephrotic-range proteinuria, mutations or aHUS-risk haplotypes involving genes encoding alternative complement regulatory proteins in some patients and inflammatory triggers associated with systemic immune-mediated diseases.

NGAL (Lcn2) monomer is associated with tubulointerstitial damage in chronic kidney disease.

The type and the extent of tissue damage inform the prognosis of chronic kidney disease (CKD), but kidney biopsy is not a routine test. Urinary tests that correlate with specific histological findings might serve as surrogates for the kidney biopsy. We used immunoblots and ARCHITECT-NGAL assays to define the immunoreactivity of urinary neutrophil gelatinase-associated lipocalin (NGAL) in CKD, and we used mass spectroscopy to identify associated proteins. We analyzed kidney biopsies to determine whether specific pathological characteristics associated with the monomeric NGAL species. Advanced CKD urine contained the NGAL monomer as well as novel complexes of NGAL. When these species were separated, we found a significant correlation between the NGAL monomer and glomerular filtration rate (r=-0.53, P<0.001), interstitial fibrosis (mild vs. severe disease; mean 54 vs. 167 µg uNGAL/g Cr, P<0.01), and tubular atrophy (mild vs. severe disease; mean 54 vs. 164 µg uNGAL/g Cr, P<0.01). Monospecific assays of the NGAL monomer demonstrated a correlation with histology that typifies progressive, severe CKD.

Membrano-proliferative glomerulonephritis, atypical hemolytic uremic syndrome, and a new complement factor H mutation: report of a case.

BACKGROUND: Complement protein factor H (CFH) is a regulatory protein of the alternative complement pathway (AP); CFH mutations lead to a spectrum of different phenotypical manifestations of renal disease. CASE-DIAGNOSIS/TREATMENT: We report the case of a boy with a novel CFH gene mutation who presented with a membranoproliferative (MPGN) pattern of glomerular injury and developed 2 years later atypical hemolytic uremic syndrome (aHUS); this description shows that CFH alteration leads to two different renal diseases in the same patient. CONCLUSIONS: Our case suggests the possibility that complement dysregulation could determine different renal conditions, which may be part of the same disease spectrum. Early recognition of an evolution of glomerulopathies into aHUS may allow appropriate management and prevention of life-threatening consequences.

Exome sequencing identified MYO1E and NEIL1 as candidate genes for human autosomal recessive steroid-resistant nephrotic syndrome.

To identify gene loci associated with steroid-resistant nephrotic syndrome (SRNS), we utilized homozygosity mapping and exome sequencing in a consanguineous pedigree with three affected siblings. High-density genotyping identified three segments of homozygosity spanning 33.6 Mb on chromosomes 5, 10, and 15 containing 296 candidate genes. Exome sequencing identified two homozygous missense variants within the chromosome 15 segment; an A159P substitution in myosin 1E (MYO1E), encoding a podocyte cytoskeletal protein; and an E181K substitution in nei endonuclease VIII-like 1 (NEIL1), encoding a base-excision DNA repair enzyme. Both variants disrupt highly conserved protein sequences and were absent in public databases, 247 healthy controls, and 286 patients with nephrotic syndrome. The MYO1E A159P variant is noteworthy, as it is expected to impair ligand binding and actin interaction in the MYO1E motor domain. The predicted loss of function is consistent with the previous demonstration that Myo1e inactivation produces nephrotic syndrome in mice. Screening 71 additional patients with SRNS, however, did not identify independent NEIL1 or MYO1E mutations, suggesting larger sequencing efforts are needed to uncover which mutation is responsible for the phenotype. Our findings demonstrate the utility of exome sequencing for rapidly identifying candidate genes for human SRNS.

Addition of azathioprine to corticosteroids does not benefit patients with IgA nephropathy.

The optimal treatment for IgA nephropathy (IgAN) remains unknown. Some patients respond to corticosteroids, suggesting that more aggressive treatment may provide additional benefit. We performed a randomized, multicenter, controlled trial to determine whether adding azathioprine to steroids improves renal outcome. We randomly assigned 207 IgAN patients with creatinine ≤2.0 mg/dl and proteinuria ≥1.0 g/d to either (1) a 3-day pulse of methylprednisolone in months 1, 3, and 5 in addition to both oral prednisone 0.5 mg/kg every other day and azathioprine 1.5 mg/kg per day for 6 months (n = 101, group 1) or (2) steroids alone on the same schedule (n = 106, group 2). The primary outcome was renal survival (time to 50% increase in plasma creatinine from baseline); secondary outcomes were changes in proteinuria over time and safety. After a median follow-up of 4.9 years, the primary endpoint occurred in 13 patients in group 1 (12.9%, 95% CI 7.5 to 20.9%) and 12 patients in group 2 (11.3%, CI 6.5 to 18.9%) (P = 0.83). Five-year cumulative renal survival was similar between groups (88 versus 89%; P = 0.83). Multivariate Cox regression analysis revealed that female gender, systolic BP, number of antihypertensive drugs, ACE inhibitor use, and proteinuria during follow-up predicted the risk of reaching the primary endpoint. Treatment significantly decreased proteinuria from 2.00 to 1.07 g/d during follow-up (P < 0.001) on average, with no difference between groups. Treatment-related adverse events were more frequent among those receiving azathioprine. In summary, adding low-dose azathioprine to corticosteroids for 6 months does not provide additional benefit to patients with IgAN and may increase the risk for adverse events.

Autoimmunity in membranous nephropathy targets aldose reductase and SOD2.

Glomerular targets of autoimmunity in human membranous nephropathy are poorly understood. Here, we used a combined proteomic approach to identify specific antibodies against podocyte proteins in both serum and glomeruli of patients with membranous nephropathy (MN). We detected specific anti-aldose reductase (AR) and anti-manganese superoxide dismutase (SOD2) IgG(4) in sera of patients with MN. We also eluted high titers of anti-AR and anti-SOD2 IgG(4) from microdissected glomeruli of three biopsies of MN kidneys but not from biopsies of other glomerulonephritides characterized by IgG deposition (five lupus nephritis and two membranoproliferative glomerulonephritis). We identified both antigens in MN biopsies but not in other renal pathologies or normal kidney. Confocal and immunoelectron microscopy (IEM) showed co-localization of anti-AR and anti-SOD2 with IgG(4) and C5b-9 in electron-dense podocyte immune deposits. Preliminary in vitro experiments showed an increase of SOD2 expression on podocyte plasma membrane after treatment with hydrogen peroxide. In conclusion, our data support AR and SOD2 as renal antigens of human MN and suggest that oxidative stress may drive glomerular SOD2 expression.

Urinary NGAL marks cystic disease in HIV-associated nephropathy.

Nephrosis and a rapid decline in kidney function characterize HIV-associated nephropathy (HIVAN). Histologically, HIVAN is a collapsing focal segmental glomerulosclerosis with prominent tubular damage. We explored the expression of neutrophil gelatinase-associated lipocalin (NGAL), a marker of tubular injury, to determine whether this protein has the potential to aid in the noninvasive diagnosis of HIVAN. We found that expression of urinary NGAL was much higher in patients with biopsy-proven HIVAN than in HIV-positive and HIV-negative patients with other forms of chronic kidney disease. In the HIV-transgenic mouse model of HIVAN, NGAL mRNA was abundant in dilated, microcystic segments of the nephron. In contrast, urinary NGAL did not correlate with proteinuria in human or in mouse models. These data show that marked upregulation of NGAL accompanies HIVAN and support further study of uNGAL levels in large cohorts to aid in the noninvasive diagnosis of HIVAN and screen for HIVAN-related tubular damage.

Neutrophil Extracellular Traps Profiles in Patients with Incident Systemic Lupus Erythematosus and Lupus Nephritis.

OBJECTIVE: Neutrophil extracellular traps (NET) expose modified antigens for autoantibodies in vasculitis. Little is known about levels and removal pathways of NET in systemic lupus erythematosus (SLE), especially in lupus nephritis (LN). We determined circulating levels and defined NET removal in large subsets of patients with incident SLE (iSLE), some of whom had new-onset nephritis. METHODS: Serum levels of NET (ELISA), DNase1/DNase1L3 (ELISA), and DNase activity (functional assay) were determined in 216 patients with iSLE [103 had incident LN (iLN)], in 50 patients with other primary glomerulonephritis, and in healthy controls. Ex vivo NET production by neutrophils purified from a random selection of patients was quantified as elastase/DNA release and by immunofluorescence techniques. RESULTS: Serum NET levels were very high in iSLE/iLN compared to all groups of controls and correlated with anti-dsDNA, C3-C4, and proteinuria; iLN had the highest levels. DNase activity was decreased in iLN compared to SLE (20% had one-half DNase activity) despite similar serum levels of DNase1/DNase1L3. In these cases, pretreatment of serum with protein A restored DNase efficiency; 1 patient was homozygous for a c.289_290delAC variant of DNASE1L3. Ex vivo NET production by neutrophils purified from LN, SLE, and normal controls was similar in all cases. CONCLUSION: Patients with iLN have increased circulating NET and reduced DNase activity, the latter being explained by the presence of inhibitory substances in circulation and/or by rare DNase1L3 mutations. Accumulation of NET derives from a multifactorial mechanism, and is associated and may contribute to disease severity in SLE, in particular to renal lesions. (Clinical trial registration: The Zeus study was registered at ClinicalTrials.gov, study number NCT02403115).

Renal outcome in patients with congenital anomalies of the kidney and urinary tract.

Congenital Anomalies of the Kidney and Urinary Tract (CAKUT) are a major cause of morbidity in children. We measured the risk of progression to end-stage renal disease in 312 patients with CAKUT preselected for the presence of anomalies in kidney number or size. A model of dialysis-free survival from birth was established as a function of the renal CAKUT categories of solitary kidney; unilateral and bilateral hypodysplasia; renal hypodysplasia associated with posterior urethral valves; and multicystic and horseshoe kidney. Cox regression analysis took into account the concomitant presence of vesicoureteral reflux, year of diagnosis, and time-varying values of serum creatinine, proteinuria, and hypertension. By 30 years of age, 58 patients had started dialysis, giving a yearly incidence of 0.023 over a combined 2474 patient risk years. The risk for dialysis was significantly higher for patients with a solitary kidney or with renal hypodysplasia associated with posterior urethral valves (hazard ratios of 2.43 and 5.1, respectively) compared to patients with unilateral or bilateral renal hypodysplasia, or multicystic or horseshoe kidney, and was independent of other prognostic factors. Our study shows that sub-clinical defects of the solitary kidney may be responsible for a poorer prognosis compared to more benign forms of CAKUT. Prospective studies are needed to validate these results.

Alterations of type IV collagen alpha chains in patients with chronic acquired glomerulopathies: mRNA levels, protein expression and urinary loss.

BACKGROUND: Type IV collagen is a major structural component of the normal kidney glomerulus. However, its role in chronic acquired glomerulopathies has been only partially elucidated. METHODS: Urinary levels of col(IV)alpha1, col(IV)alpha3 and col(IV)alpha5 collagen chains were analyzed in 107 patients with chronic acquired glomerulopathies. In a subgroup of 33 patients, tissue mRNA levels, protein expression and urinary excretion were evaluated for all col(IV)alpha chains, from col(IV)alpha1 to col(IV)alpha5. The renal specimens were examined to get a semiquantitative score of the acute and chronic activity of the histological lesions. Urines obtained from 13 healthy subjects and 10 normal renal tissue samples were used as controls. RESULTS: Urinary levels of col(IV)alpha1, col(IV)alpha3, col(IV)alpha5 chains were significantly higher in patients than in controls [p < 0.01 for all], while only col(IV)alpha1 and col(IV)alpha3 urinary excretion correlated with the degree of chronic histological damage [col(IV)alpha1 R = 0.44, p < 0.001; col(IV)alpha3: R = 0.47, p < 0.001]. Compared with controls, patients showed a renal expression of mRNA for col(IV)alpha5 chain significantly higher [p = 0.001], while having a significantly lower protein expression of col(IV)alpha3, col(IV)alpha4 and col(IV)alpha5 chains [p < 0.01 for all]. CONCLUSION: Patients with chronic acquired glomerulopathies show important alterations in the col(IV)alpha chain network mimicking some molecular features of the X-linked Alport's syndrome. Further studies are needed to show whether urinary levels of the col(IV)alpha chains may be used as markers for monitoring renal injury.

HCV-related cryoglobulinemic glomerulonephritis: implications of antiviral and immunosuppressive therapies.

The most frequent renal involvement in patients with chronic hepatitis C virus (HCV) infection is cryoglobulinemic glomerulonephritis, with type I membranoproliferative glomerulonephritis (MPGN) being the predominant histological pattern. The pathogenesis of HCV-related cryoglobulinemic MPGN is unknown, but the glomerular damage may be due to the deposition of immune complexes of HCV, IgG, and IgM rheumatoid factors. Clinically, cryoglobulinemic MPGN may range from isolated proteinuria to overt nephritic or nephrotic syndrome, with variable progression to chronic renal insufficiency. The management of cryoglobulinemic MPGN is difficult; the eradication of HCV by means of antiviral therapy (peginterferon plus ribavirin) leads to clinical remission in a proportion of patients, but severe renal disease may be resistant to antiviral therapy. In such cases, corticosteroids and immunosuppressive agents have been used to decrease cryoglobulin production and improve the vasculitic manifestations, but long-lasting remission of the renal disease is uncommon. Here we describe four patients with HCV-related cryoglobulinemic MPGN and the strategies used for their management. The principal message provided by these illustrative cases is that antiviral therapy alone can be the first-line treatment for patients with mild-to-moderate kidney involvement, whereas a short-term course of corticosteroids and cytotoxic agents followed by antiviral therapy may be a reasonable therapeutic strategy for patients with severe/active renal disease.

Rare functional variants of podocin (NPHS2) promoter in patients with nephrotic syndrome.

Podocin (NPHS2) is a component of the glomerular slit-diaphragm, with major regulatory functions in renal permeability of proteins. Loss of podocin and decrease in resynthesis may influence the outcome of proteinuric renal disease such as segmental glomerulosclerosis (FSGS), and promoter functionality plays a key role in this process. NPHS2 promoter variants with functional activity may be a part of the problem of podocin resynthesis. We sequenced NPHS2 promoter region from -628 to ATG in a large cohort of 260 nephrotic patients (161 with FSGS) who were presenting proteinuria from moderate to severe and were receiving or had received modular therapies according to their sensitivity to steroids and other immune modulators. Three sequence variants (-236C>T, -52C>G, -26C>G) were identified in our study population that gave an allele frequency below 1% (5 patients out of 520 alleles). Functional implications were shown for each variants that were most evident for -52C>G and -26C>G (-50% of luciferase expression compared to the wild-type sequence, p < 0.01). Consensus analysis for homology of the -52 region with regulatory factors revealed homology for USF1 and the sum of experiments with gel retardation and with cells silenced for USF1 confirmed that this factor regulates NPHS2 expression at this site. In conclusion, three functional variants in NPHS2 promoter have been identified in a large cohort of patients with nephrotic syndrome and FSGS that have a frequency <1%. One of these (i.e., -52C>G) is associated with a poor clinical outcome and evolution to end-stage renal failure. USF1 was identified as the transcriptional factor regulating NPHS2 at this site. Even if not sufficient to cause FSGS per se, these variants could represent modifiers for severity and/or progression of the disease.