A novel COL4A5 splicing mutation causes alport syndrome in a Chinese family.

BACKGROUND: Alport syndrome (AS) is characterised by haematuria, proteinuria, a gradual decline in kidney function, hearing loss, and eye abnormalities. The disease is caused by mutations in COL4An (n = 3, 4, 5) that encodes 3-5 chains of type IV collagen in the glomerular basement membrane. AS has three genetic models: X-linked, autosomal recessive, and autosomal dominant. The most common type of AS is X-linked AS, which is caused by COL4A5. METHODS: We enrolled children with renal insufficiency and a family history of kidney disorders. The proband was identified using whole-exome sequencing. Sanger sequencing was performed to verify the mutation site. Minigene technology was used to analyse the influence of mutant genes on pre-mRNA shearing, and the Iterative Threading ASSEmbly Refinement (I-TASSER) server was used to analyse the protein structure changes. RESULTS: The proband, together with her mother and younger brother, displayed microscopic haematuria and proteinuria, Pathological examination revealed mesangial hyperplasia and sclerosis. A novel mutation (NM_000495.5 c.4298-8G > A) in the intron of the COL4A5 gene in the proband was discovered, which was also present in the proband's mother, brother, and grandmother. In vitro minigene expression experiments verified that the c.4298-8G > A mutation caused abnormal splicing, leading to the retention of six base pairs at the end of intron 46. The I-TASSER software predicted that the mutation affected the hydrogen-bonding structure of COL4A5 and the electrostatic potential on the surface of the protein molecules. CONCLUSIONS: Based on the patient's clinical history and genetic traits, we conclude that the mutation at the splicing site c.4298-8G > A of the COL4A5 gene is highly probable to be the underlying cause within this particular family. This discovery expands the genetic spectrum and deepens our understanding of the molecular mechanisms underlying AS.

The spatially resolved transcriptome signatures of glomeruli in chronic kidney disease.

Here, we used digital spatial profiling (DSP) to describe the glomerular transcriptomic signatures that may characterize the complex molecular mechanisms underlying progressive kidney disease in Alport syndrome, focal segmental glomerulosclerosis, and membranous nephropathy. Our results revealed significant transcriptional heterogeneity among diseased glomeruli, and this analysis showed that histologically similar glomeruli manifested different transcriptional profiles. Using glomerular pathology scores to establish an axis of progression, we identified molecular pathways with progressively decreased expression in response to increasing pathology scores, including signal recognition particle-dependent cotranslational protein targeting to membrane and selenocysteine synthesis pathways. We also identified a distinct signature of upregulated and downregulated genes common to all the diseases investigated when compared with nondiseased tissue from nephrectomies. These analyses using DSP at the single-glomerulus level could help to increase insight into the pathophysiology of kidney disease and possibly the identification of biomarkers of disease progression in glomerulopathies.

Multidisciplinary management improves the genetic diagnosis of hereditary kidney diseases in the next generation sequencing (NGS) era.

BACKGROUND AND OBJECTIVE: Hereditary kidney diseases (HKD) are a frequent cause of chronic kidney disease, and their diagnosis has increased since the introduction of next generation sequencing (NGS). In 2018, the Multidisciplinary Unit for Hereditary Kidney Diseases of the Region of Murcia (UMERH-RM) was founded based on the genetic study of HKD. The objective of this study is to analyze the results obtained in the first 3 years of operation, and to analyze the clinical factors associated to a final genetic diagnosis. MATERIALS AND METHODS: All the patients studied with the HKD gene panel were included. The characteristics between those who obtained a final genetic diagnosis and those who did not were compared. RESULTS: A total of 360 patients were studied, detecting genetic variants in 164 not related patients (45.6%). 45 of these were variants of uncertain significance requiring a family co-segregation study, which was facilitated by the multidisciplinary unit. Overall, considering the results obtained with the NGS panel and the extended genomic studies, a final diagnostic yield of HRD of 33.3% (120/360) was achieved, and including incidental findings 35.6% (128/360). Two hundred and twenty-three patients with suspected Alport syndrome were studied. Diagnosis was confirmed in 28.5% (COL4A4 most frequent gene), more frequently women with an obvious compatible family history. They also had frequently microhematuria, although 5 patients without microhematuria confirmed the diagnosis. There were no differences in age, proteinuria, renal function, hearing loss, or ophthalmologic abnormalities. The most frequent finding in the renal biopsy was mesangial proliferation. We estimate that 39 patients avoided renal biopsy. A total of 101 patients with suspected PKD were also studied, 49.5% had a conclusive genetic result (most frequent gene PKD1), more frequently women, with larger kidney sizes (although 9 patients with normal kidney size confirmed diagnosis). Again, the most predictive characteristic of genetic outcome was family history. CONCLUSIONS: The implementation of an NGS panel for HKD, together with the multidisciplinary approach to cases, has improved the diagnostic performance of HKD. In our sample, autosomal dominant Alport syndrome is of highest incidence. Ophthalmological and auditory examinations did not contribute to the diagnosis. We have seen a significant decrease in the indication of renal biopsies thanks to molecular diagnosis. The multidisciplinary approach, with the active participation of nephrologists, paediatricians, clinical and molecular geneticists, with insistence on adequate patient phenotyping and review of their family history, offers a better interpretation of genetic variants, allowing reclassification of the diagnosis of some nephropathies, thus improving their management and genetic advice.

In chronic kidney disease altered cardiac metabolism precedes cardiac hypertrophy.

Conduit arterial disease in chronic kidney disease (CKD) is an important cause of cardiac complications. Cardiac function in CKD has not been studied in the absence of arterial disease. In an Alport syndrome model bred not to have conduit arterial disease, mice at 225 days of life (dol) had CKD equivalent to humans with CKD stage 4-5. Parathyroid hormone (PTH) and FGF23 levels were one log order elevated, circulating sclerostin was elevated, and renal activin A was strongly induced. Aortic Ca levels were not increased, and vascular smooth muscle cell (VSMC) transdifferentiation was absent. The CKD mice were not hypertensive, and cardiac hypertrophy was absent. Freshly excised cardiac tissue respirometry (Oroboros) showed that ADP-stimulated O2 flux was diminished from 52 to 22 pmol/mg (P = 0.022). RNA-Seq of cardiac tissue from CKD mice revealed significantly decreased levels of cardiac mitochondrial oxidative phosphorylation genes. To examine the effect of activin A signaling, some Alport mice were treated with a monoclonal Ab to activin A or an isotype-matched IgG beginning at 75 days of life until euthanasia. Treatment with the activin A antibody (Ab) did not affect cardiac oxidative phosphorylation. However, the activin A antibody was active in the skeleton, disrupting the effect of CKD to stimulate osteoclast number, eroded surfaces, and the stimulation of osteoclast-driven remodeling. The data reported here show that cardiac mitochondrial respiration is impaired in CKD in the absence of conduit arterial disease. This is the first report of the direct effect of CKD on cardiac respiration.NEW & NOTEWORTHY Heart disease is an important morbidity of chronic kidney disease (CKD). Hypertension, vascular stiffness, and vascular calcification all contribute to cardiac pathophysiology. However, cardiac function in CKD devoid of vascular disease has not been studied. Here, in an animal model of human CKD without conduit arterial disease, we analyze cardiac respiration and discover that CKD directly impairs cardiac mitochondrial function by decreasing oxidative phosphorylation. Protection of cardiac oxidative phosphorylation may be a therapeutic target in CKD.

PDGF-D Is Dispensable for the Development and Progression of Murine Alport Syndrome.

Alport syndrome is an inherited kidney disease, which can lead to glomerulosclerosis and fibrosis, as well as end-stage kidney disease in children and adults. Platelet-derived growth factor-D (PDGF-D) mediates glomerulosclerosis and interstitial fibrosis in various models of kidney disease, prompting investigation of its role in a murine model of Alport syndrome. In vitro, PDGF-D induced proliferation and profibrotic activation of conditionally immortalized human parietal epithelial cells. In Col4a3-/- mice, a model of Alport syndrome, PDGF-D mRNA and protein were significantly up-regulated compared with non-diseased wild-type mice. To analyze the therapeutic potential of PDGF-D inhibition, Col4a3-/- mice were treated with a PDGF-D neutralizing antibody. Surprisingly, PDGF-D antibody treatment had no effect on renal function, glomerulosclerosis, fibrosis, or other indices of kidney injury compared with control treatment with unspecific IgG. To characterize the role of PDGF-D in disease development, Col4a3-/- mice with a constitutive genetic deletion of Pdgfd were generated and analyzed. No difference in pathologic features or kidney function was observed in Col4a3-/-Pdgfd-/- mice compared with Col4a3-/-Pdgfd+/+ littermates, confirming the antibody treatment data. Mechanistically, lack of proteolytic PDGF-D activation in Col4a3-/- mice might explain the lack of effects in vivo. In conclusion, despite its established role in kidney fibrosis, PDGF-D, without further activation, does not mediate the development and progression of Alport syndrome in mice.

Quantitative assessment of glomerular basement membrane collagen IV α chains in paraffin sections from patients with focal segmental glomerulosclerosis and Alport gene variants.

Focal segmental glomerulosclerosis (FSGS) lesions have been linked to variants in COL4A3/A4/A5 genes, which are also mutated in Alport syndrome. Although it could be useful for diagnosis, quantitative evaluation of glomerular basement membrane (GBM) type IV collagen (colIV) networks is not widely used to assess these patients. To do so, we developed immunofluorescence imaging for collagen α5(IV) and α1/2(IV) on kidney paraffin sections with Airyscan confocal microscopy that clearly distinguishes GBM collagen α3α4α5(IV) and α1α1α2(IV) as two distinct layers, allowing quantitative assessment of both colIV networks. The ratios of collagen α5(IV):α1/2(IV) mean fluorescence intensities (α5:α1/2 intensity ratios) and thicknesses (α5:α1/2 thickness ratios) were calculated to represent the levels of collagen α3α4α5(IV) relative to α1α1α2(IV). The α5:α1/2 intensity and thickness ratios were comparable across all 11 control samples, while both ratios were significantly and markedly decreased in all patients with pathogenic or likely pathogenic Alport COL4A variants, supporting validity of this approach. Thus, with further validation of this technique, quantitative measurement of GBM colIV subtype abundance by immunofluorescence, may potentially serve to identify the subgroup of patients with FSGS lesions likely to harbor pathogenic COL4A variants who could benefit from genetic testing.

[Long-term auditory monitoring in children with Alport syndrome based on different degrees of renal injury].

Objective:To investigate long-term auditory changes and characteristics of Alport syndrome（AS） patients with different degrees of renal injury. Methods:Retrospectively analyzing clinical data of patients diagnosed AS from January 2007 to September 2022, including renal pathology, genetic detection and hearing examination. A long-term follow-up focusing on hearing and renal function was conducted. Results:This study included 70 AS patients, of which 33（25 males, 8 females, aged 3.4-27.8 years） were followed up, resulting in a loss rate of 52.9%.The follow-up period ranged from 1.1to 15.8 years, with 16 patients followed-up for over 10 years. During the follow-up, 10 patients presenting with hearing abnormalities at the time of diagnosis of AS had progressive hearing loss, and 3 patients with new hearing abnormalities were followed up, which appeared at 5-6 years of disease course. All of which were sensorineural deafness. While only 3 patients with hearing abnormalities among 13 patients received hearing aid intervention. Of these patients,7 developed end-stage renal disease（ESRD）, predominantly males （6/7）. The rate of long-term hearing loss was significantly different between ESRD group and non-ESRD group（P=0.013）. There was no correlation between the progression of renal disease and long-term hearing level（P>0.05）. kidney biopsies from 28 patients revealed varying degrees of podocyte lesion and uneven thickness of basement membrane. The severity of podocyte lesion was correlated with the rate of long-term hearing loss（P=0.048）, and there was no correlation with the severity of hearing loss（P>0.05）. Among 11 cases, theCOL4A5mutationwas most common （8 out of 11）, but there was no significant correlation between the mutation type and hearing phenotype（P>0.05）. Conclusion:AS patients exhibit progressive hearing loss with significant heterogeneity over the long-term.. THearing loss is more likely to occur 5-6 years into the disease course. Hearing abnormalities are closely related to renal disease status, kidney tissue pathology, and gene mutations, emphasizing the need for vigilant long-term hearing follow-up and early intervention.

Long-term auditory monitoring in children with Alport syndrome based on different degrees of renal injury / 临床耳鼻咽喉头颈外科杂志

Objective:To investigate long-term auditory changes and characteristics of Alport syndrome（AS） patients with different degrees of renal injury. Methods:Retrospectively analyzing clinical data of patients diagnosed AS from January 2007 to September 2022, including renal pathology, genetic detection and hearing examination. A long-term follow-up focusing on hearing and renal function was conducted. Results:This study included 70 AS patients, of which 33（25 males, 8 females, aged 3.4-27.8 years） were followed up, resulting in a loss rate of 52.9%.The follow-up period ranged from 1.1to 15.8 years, with 16 patients followed-up for over 10 years. During the follow-up, 10 patients presenting with hearing abnormalities at the time of diagnosis of AS had progressive hearing loss, and 3 patients with new hearing abnormalities were followed up, which appeared at 5-6 years of disease course. All of which were sensorineural deafness. While only 3 patients with hearing abnormalities among 13 patients received hearing aid intervention. Of these patients,7 developed end-stage renal disease（ESRD）, predominantly males （6/7）. The rate of long-term hearing loss was significantly different between ESRD group and non-ESRD group（P=0.013）. There was no correlation between the progression of renal disease and long-term hearing level（P>0.05）. kidney biopsies from 28 patients revealed varying degrees of podocyte lesion and uneven thickness of basement membrane. The severity of podocyte lesion was correlated with the rate of long-term hearing loss（P=0.048）, and there was no correlation with the severity of hearing loss（P>0.05）. Among 11 cases, theCOL4A5mutationwas most common （8 out of 11）, but there was no significant correlation between the mutation type and hearing phenotype（P>0.05）. Conclusion:AS patients exhibit progressive hearing loss with significant heterogeneity over the long-term.. THearing loss is more likely to occur 5-6 years into the disease course. Hearing abnormalities are closely related to renal disease status, kidney tissue pathology, and gene mutations, emphasizing the need for vigilant long-term hearing follow-up and early intervention.

Pregnancy in women with autosomal recessive Alport syndrome caused by novel compound heterozygous mutations of COL4A3 gene: Two cases reports.

RATIONALE: Autosomal recessive Alport syndrome (ARAS) is an hereditary heterogeneous disease that poses a serious risk to pregnant women. PATIENT CONCERNS: We reported 2 cases of pregnancy with progressive proteinuria. The case 1 was a 21-year-old woman with 24-h proteinuria increased from 2.03 to 11.72 g at 13 to 35 weeks of gestation, and the case 2 was a 28-year-old woman with 24-h proteinuria increased from 2.10 to 9.32 g at 8 to 36 weeks of gestation. In advanced stage of pregnancy, the fetal development was smaller than the gestational age. DIAGNOSES: Sanger sequencing showed that novel compound heterozygous mutations [c.1315 G>T (p.G439C) and c.4847 G>A (p.C1616Y)] of the collagen type IV alpha 3 chain (COL4A3) gene were found in the 2 cases. Renal puncture pathology confirmed the diagnosis of ARAS. INTERVENTIONS: The 2 cases were treated with albumin, compounded amino acids, calcium, vitamin D, and low molecular weight heparin in addition to conventional treatment during pregnancy. Pregnancy was terminated by cesarean section at 36 to 37 weeks of gestation. After delivery, the patients were treated with Losartan for anti-proteinuric therapy for 1 year. OUTCOMES: The neonatal weights and Apgar scores were normal. The patients recovered well and 24-h proteinuria decreased to pre-pregnancy level. LESSONS: When pregnant women present with a persistent increasing proteinuria, ARAS needs to be considered. Sanger sequencing is useful to assist in the diagnosis of ARAS. Multidisciplinary treatments from nephrologists and gynecologists are needed to ensure the safety of pregnancy and the fetus.

Ascending aortic aneurysm and histopathology in Alport syndrome: a case report.

BACKGROUND: Alport syndrome (AS) is caused by mutations in type IV collagen genes that typically target and compromise the integrity of basement membranes in kidney, ocular, and sensorineural cochlear tissues. Type IV and V collagens are also integral components of arterial walls, and whereas collagenopathies including AS are implicated in aortic disease, the incidence of aortic aneurysm in AS is unknown probably because of underreporting. Consequently, AS is not presently considered an independent risk factor for aortic aneurysm and more detailed case studies including histological evidence of basement membrane abnormalities are needed to determine such a possible linkage. CASE PRESENTATION: Here, we present unique histopathological findings of an ascending aortic aneurysm collected at the time of surgery from an AS patient wherein hypertension was the only other known risk factor. CONCLUSIONS: The studies reveal classical histological features of aortic aneurysm, including atheroma, lymphocytic infiltration, elastin disruption, and myxoid degeneration with probable AS association.

[COL4A5 genotypes and clinical characteristics of children with Alport syndrome]. / 儿童Alport综合征COL4A5åŸºå› åž‹åŠä¸´åºŠç‰¹ç‚¹åˆ†æž.

OBJECTIVES: To investigate the genotypes of the pathogenic gene COL4A5 and the characteristics of clinical phenotypes in children with Alport syndrome (AS). METHODS: A retrospective analysis was performed for the genetic testing results and clinical data of 19 AS children with COL4A5 gene mutations. RESULTS: Among the 19 children with AS caused by COL4A5 gene mutations, 1 (5%) carried a new mutation of the COL4A5 gene, i.e., c.3372A>G(p.P1124=) and presented with AS coexisting with IgA vasculitis nephritis; 3 children (16%) had large fragment deletion of the COL4A5 gene, among whom 2 children (case 7 had a new mutation site of loss51-53) had gross hematuria and albuminuria at the onset, and 1 child (case 13 had a new mutation site of loss3-53) only had microscopic hematuria, while the other 15 children (79%) had common clinical phenotypes of AS, among whom 7 carried new mutations of the COL4A5 gene. Among all 19 children, 3 children (16%) who carried COL4A5 gene mutations also had COL4A4 gene mutations, and 1 child (5%) had COL4A3 gene mutations. Among these children with double gene mutations, 2 had gross hematuria and proteinuria at the onset. CONCLUSIONS: This study expands the genotype and phenotype spectrums of the pathogenic gene COL4A5 for AS. Children with large fragment deletion of the COL4A5 gene or double gene mutations of COL4A5 with COL4A3 or COL4A4 tend to have more serious clinical manifestations.

X-linked Alport Syndrome with Type IV Collagen α5 Chain Staining Revealing Normal Expression in the Glomerular Basement Membrane and Negative on Bowman's Capsule and Distal Tubular Basement Membrane: A Case Report.

X-linked Alport syndrome is a hereditary progressive renal disease resulting from the disruption of collagen α3α4α5 (IV) heterotrimerization caused by pathogenic variants in the COL4A5 gene. This study aimed to report a male case of X-linked Alport syndrome with a mild phenotype accompanied by an atypical expression pattern of type IV collagen α5 [α5 (IV)] chain in glomerulus. A 38-year-old male presented with proteinuria (2.3 g/day) and hematuria. He has been detected urinary protein and occult blood since childhood. A renal biopsy was performed at the age of 29 years; however, a diagnosis of Alport syndrome was not considered. A renal biopsy 9 years later revealed diffuse thinning and lamellation of the glomerular basement membrane. Α staining for α5 (IV) revealed a normal expression pattern in the glomerular basement membrane and a complete negative expression in Bowman's capsule and distal tubular basement membrane. Using next-generation sequencing, we detected a COL4A5 missense variant within exon 35 (NM_000495.5: c.3088G>A, p. G1030S). The possibility of X-linked Alport syndrome should be considered when negative expression of α5 (IV) staining on Bowman's capsule was observed.

Finerenone Added to RAS/SGLT2 Blockade for CKD in Alport Syndrome. Results of a Randomized Controlled Trial with Col4a3-/- Mice.

SIGNIFICANCE STATEMENT: We hypothesized that triple therapy with inhibitors of the renin-angiotensin system (RAS), sodium-glucose transporter (SGLT)-2, and the mineralocorticoid receptor (MR) would be superior to dual RAS/SGLT2 blockade in attenuating CKD progression in Col4a3 -deficient mice, a model of Alport syndrome. Late-onset ramipril monotherapy or dual ramipril/empagliflozin therapy attenuated CKD and prolonged overall survival by 2 weeks. Adding the nonsteroidal MR antagonist finerenone extended survival by 4 weeks. Pathomics and RNA sequencing revealed significant protective effects on the tubulointerstitium when adding finerenone to RAS/SGLT2 inhibition. Thus, triple RAS/SGLT2/MR blockade has synergistic effects and might attenuate CKD progression in patients with Alport syndrome and possibly other progressive chronic kidney disorders. BACKGROUND: Dual inhibition of the renin-angiotensin system (RAS) plus sodium-glucose transporter (SGLT)-2 or the mineralocorticoid receptor (MR) demonstrated additive renoprotective effects in large clinical trials. We hypothesized that triple therapy with RAS/SGLT2/MR inhibitors would be superior to dual RAS/SGLT2 blockade in attenuating CKD progression. METHODS: We performed a preclinical randomized controlled trial (PCTE0000266) in Col4a3 -deficient mice with established Alport nephropathy. Treatment was initiated late (age 6 weeks) in mice with elevated serum creatinine and albuminuria and with glomerulosclerosis, interstitial fibrosis, and tubular atrophy. We block-randomized 40 male and 40 female mice to either nil (vehicle) or late-onset food admixes of ramipril monotherapy (10 mg/kg), ramipril plus empagliflozin (30 mg/kg), or ramipril plus empagliflozin plus finerenone (10 mg/kg). Primary end point was mean survival. RESULTS: Mean survival was 63.7±10.0 days (vehicle), 77.3±5.3 days (ramipril), 80.3±11.0 days (dual), and 103.1±20.3 days (triple). Sex did not affect outcome. Histopathology, pathomics, and RNA sequencing revealed that finerenone mainly suppressed the residual interstitial inflammation and fibrosis despite dual RAS/SGLT2 inhibition. CONCLUSION: Experiments in mice suggest that triple RAS/SGLT2/MR blockade may substantially improve renal outcomes in Alport syndrome and possibly other progressive CKDs because of synergistic effects on the glomerular and tubulointerstitial compartments.

A wave of deep intronic mutations in X-linked Alport syndrome.

X-linked Alport syndrome (XLAS) is an inherited kidney disease caused exclusively by pathogenic variants in the COL4A5 gene. In 10-20% of cases, DNA sequencing of COL4A5 exons or flanking regions cannot identify molecular causes. Here, our objective was to use a transcriptomic approach to identify causative events in a group of 19 patients with XLAS without identified mutation by Alport gene panel sequencing. Bulk RNAseq and/or targeted RNAseq using a capture panel of kidney genes was performed. Alternative splicing events were compared to those of 15 controls by a developed bioinformatic score. When using targeted RNAseq, COL4A5 coverage was found to be 23-fold higher than with bulk RNASeq and revealed 30 significant alternative splicing events in 17 of the 19 patients. After computational scoring, a pathogenic transcript was found in all patients. A causative variant affecting COL4A5 splicing and absent in the general population was identified in all cases. Altogether, we developed a simple and robust method for identification of aberrant transcripts due to pathogenic deep-intronic COL4A5 variants. Thus, these variants, potentially targetable by specific antisense oligonucleotide therapies, were found in a high percentage of patients with XLAS in whom pathogenic variants were missed by conventional DNA sequencing.

Genetic features and kidney morphological changes in women with X-linked Alport syndrome.

BACKGROUND: X-linked Alport syndrome (XLAS) caused by COL4A5 pathogenic variants usually has heterogeneous phenotypes in female patients. The genetic characteristics and glomerular basement membrane (GBM) morphological changes in women with XLAS need to been further investigated. METHODS: A total of 83 women and 187 men with causative COL4A5 variants were enrolled for comparative analysis. RESULTS: Women were more frequently carrying de novo COL4A5 variants compared with men (47% vs 8%, p=0.001). The clinical manifestations in women were variable, and no genotype-phenotype correlation was observed. Coinherited podocyte-related genes, including TRPC6, TBC1D8B, INF2 and MYH9, were identified in two women and five men, and the modifying effects of coinherited genes contributed to the heterogeneous phenotypes in these patients. X-chromosome inactivation (XCI) analysis of 16 women showed that 25% were skewed XCI. One patient preferentially expressing the mutant COL4A5 gene developed moderate proteinuria, and two patients preferentially expressing the wild-type COL4A5 gene presented with haematuria only. GBM ultrastructural evaluation demonstrated that the degree of GBM lesions was associated with the decline in kidney function for both genders, but more severe GBM changes were found in men compared with women. CONCLUSIONS: The high frequency of de novo variants carried by women indicates that the lack of family history tends to make them susceptible to be underdiagnosed. Coinherited podocyte-related genes are potential contributors to the heterogeneous phenotype of some women. Furthermore, the association between the degree of GBM lesions and decline in kidney function is valuable in evaluating the prognosis for patients with XLAS.

Molecular MR Imaging of Renal Fibrogenesis in Mice.

BACKGROUND: In most CKDs, lysyl oxidase oxidation of collagen forms allysine side chains, which then form stable crosslinks. We hypothesized that MRI with the allysine-targeted probe Gd-oxyamine (OA) could be used to measure this process and noninvasively detect renal fibrosis. METHODS: Two mouse models were used: hereditary nephritis in Col4a3-deficient mice (Alport model) and a glomerulonephritis model, nephrotoxic nephritis (NTN). MRI measured the difference in kidney relaxation rate, ΔR1, after intravenous Gd-OA administration. Renal tissue was collected for biochemical and histological analysis. RESULTS: ΔR1 was increased in the renal cortex of NTN mice and in both the cortex and the medulla of Alport mice. Ex vivo tissue analyses showed increased collagen and Gd-OA levels in fibrotic renal tissues and a high correlation between tissue collagen and ΔR1. CONCLUSIONS: Magnetic resonance imaging using Gd-OA is potentially a valuable tool for detecting and staging renal fibrogenesis.

COL4A5 genotypes and clinical characteristics of children with Alport syndrome / 中国当代儿科杂志

OBJECTIVES@#To investigate the genotypes of the pathogenic gene COL4A5 and the characteristics of clinical phenotypes in children with Alport syndrome (AS).@*METHODS@#A retrospective analysis was performed for the genetic testing results and clinical data of 19 AS children with COL4A5 gene mutations.@*RESULTS@#Among the 19 children with AS caused by COL4A5 gene mutations, 1 (5%) carried a new mutation of the COL4A5 gene, i.e., c.3372A>G(p.P1124=) and presented with AS coexisting with IgA vasculitis nephritis; 3 children (16%) had large fragment deletion of the COL4A5 gene, among whom 2 children (case 7 had a new mutation site of loss51-53) had gross hematuria and albuminuria at the onset, and 1 child (case 13 had a new mutation site of loss3-53) only had microscopic hematuria, while the other 15 children (79%) had common clinical phenotypes of AS, among whom 7 carried new mutations of the COL4A5 gene. Among all 19 children, 3 children (16%) who carried COL4A5 gene mutations also had COL4A4 gene mutations, and 1 child (5%) had COL4A3 gene mutations. Among these children with double gene mutations, 2 had gross hematuria and proteinuria at the onset.@*CONCLUSIONS@#This study expands the genotype and phenotype spectrums of the pathogenic gene COL4A5 for AS. Children with large fragment deletion of the COL4A5 gene or double gene mutations of COL4A5 with COL4A3 or COL4A4 tend to have more serious clinical manifestations.

Spectrum and Distribution of Biopsy-proven Kidney Diseases: A 12-year Survey of a Single Center in Iran.

Data about the prevalence of biopsy-proven kidney diseases in Iran are rare, and none of the previous studies used electron microscopy for diagnosis. This study aimed to analyze the prevalence of biopsy-proven kidney diseases in Iran's primary referral center. To the best of our knowledge, this is the most extensive study carried out in Iran. Reports of kidney biopsy samples from patients referred to our center in 2007-2018 were reviewed for demographic data, clinical presentation, and final diagnosis. Statistical analyses were performed. Among the 3455 samples received, 2975 were analyzed. Nephrotic syndrome (39%) was the most common cause of biopsy, followed by subnephrotic proteinuria (18%), hematuria in association with proteinuria (15%), renal failure (9%), isolated hematuria (6%), and lupus nephritis (LN) (4%). The most common diagnoses were membranous glomerulonephritis (17.9%), focal segmental glomerulosclerosis (FSGS) (15.9%), LN (13.7%), minimal histopathological findings (unsampled FSGS vs. minimal change disease, 12.1%), Immunoglobin A nephropathy (IgAN) (6.5%) and Alport syndrome (6.1%). NS and proteinuria were the most common indications for a kidney biopsy. IgAN and LN were the most common causes of primary and secondary glomerulonephritis, presenting with hematuria and proteinuria, respectively. Although membranous glomerulonephritis was the most common disease, it has been replaced by FSGS in recent years.

Genetic diagnosis and renal biopsy findings in the setting of a renal genetics clinic.

As genetic testing becomes more available, its utilization as an early diagnostic tool in nephrology is more common. The objective of the study is to examine diagnostic agreement between the renal biopsy findings and genetic diagnoses. A retrospective study was conducted in February 2022. A total of 28 patients had both genetic diagnosis and histologic results (n = 1 nephrectomy, n = 27 biopsy). We collected clinical, renal biopsy findings, and genetic information. The relationship between the histologic findings and the genetic diagnoses was classified as: concordant, nonspecific, and discordant. A total of 15 males and 13 females were included (mean age = 9.6 years). Clinical suspicion of Alport syndrome was the most common reason for referral (n = 11, 39.3%), followed by nephrotic syndrome (n = 8, 28.5%), "other" (n = 6, 21.4%), cystic kidney disease (n = 1, 3.6%), isolated hematuria (n = 1, 3.6%), and non-nephrotic proteinuria (n = 1, 3.6%). The overall concordance rate between renal histologic and genetic diagnoses was 71.4% (20/28), nonspecific biopsy results were observed in 17.9% (5/28), and discordant results were observed in 10.7% (3/28). All patients referred for suspected Alport Syndrome had pathogenic/likely pathogenic variants in one of the COL4A genes. Two cases of Lowe syndrome and one of PAX2-associated nephropathy had discordant histology findings. Agreement between renal histologic findings and genetic results varies based on the reason for referral. There was a complete agreement for patients referred for Alport Syndrome; However, there were examples that renal biopsy showed secondary findings that were not specifically associated with the underlying genetic results.