Clinical and Functional Assessment of Digenicity in Renal Phosphate Wasting

Apart from increased fluid intake, patients with kidney stone disease (KSD) due to renal phosphate wasting require specific metaphylaxis. NaPi2a, NaPi2c, and NHERF1 regulate plasma phosphate concentration by reabsorbing phosphate in proximal kidney tubules and have been found altered in monogenic hypophosphatemia with a risk of KSD. In this study, we aimed at assessing the combined genetic alterations impacting NaPi2a, NaPi2c, and NHERF1. Therefore, we screened our hereditary KSD registry for cases of oligo- and digenicity, conducted reverse phenotyping, and undertook functional studies. As a result, we identified three patients from two families with digenic alterations in NaPi2a, NaPi2c, and NHERF1. In family 1, the index patient, who presented with severe renal calcifications and a bone mineralization disorder, carried digenic alterations affecting both NaPi transporter 2a and 2c. Functional analysis confirmed an additive genetic effect. In family 2, the index patient presented with kidney function decline, distinct musculature-related symptoms, and intracellular ATP depletion. Genetically, this individual was found to harbor variants in both NaPi2c and NHERF1 pointing towards genetic interaction. In summary, digenicity and gene dosage are likely to impact the severity of renal phosphate wasting and should be taken into account in terms of metaphylaxis through phosphate substitution

Challenging Disease Ontology by Instances of Atypical PKHD1 and PKD1 Genetics

Background: Autosomal polycystic kidney disease is distinguished into dominant (ADPKD) and recessive (ARPKD) inheritance usually caused by either monoallelic (PKD1/PKD2) or biallelic (PKHD1) germline variation. Clinical presentations are genotype-dependent ranging from fetal demise to mild chronic kidney disease (CKD) in adults. Additionally, exemptions from dominant and recessive inheritance have been reported in both disorders resulting in respective phenocopies. Here, we comparatively report three young adults with microcystic-hyperechogenic kidney morphology based on unexpected genetic alterations beyond typical inheritance. Methods: Next-generation sequencing (NGS)-based gene panel analysis and multiplex ligation-dependent probe amplification (MLPA) of PKD-associated genes, familial segregation analysis, and reverse phenotyping. Results: Three unrelated individuals presented in late adolescence for differential diagnosis of incidental microcystic-hyperechogenic kidneys with preserved kidney and liver function. Upon genetic analysis, we identified a homozygous hypomorphic PKHD1 missense variant causing pseudodominant inheritance in a family, a large monoallelic PKDH1-deletion with atypical transmission, and biallelic PKD1 missense hypomorphs with recessive inheritance. Conclusion: By this report, we illustrate clinical presentations associated with atypical PKD-gene alterations beyond traditional modes of inheritance. Large monoallelic PKHD1-alterations as well as biallelic hypomorphs of both PKD1 and PKHD1 may lead to mild CKD in the absence of prominent macrocyst formation and functional liver impairment. The long-term renal prognosis throughout life, however, remains undetermined. Increased detection of atypical inheritance challenges our current thinking of disease ontology not only in PKD but also in Mendelian disorders in general

Delta weight loss unlike genetic variation associates with hyperoxaluria after malabsorptive bariatric surgery

The risk of enteric hyperoxaluria is significantly increased after malabsorptive bariatric surgery (MBS). However, its underlying determinants are only poorly characterized. In this case-control study, we aimed at identifying clinical and genetic factors to dissect their individual contributions to the development of post-surgical hyperoxaluria. We determined the prevalence of hyperoxaluria and nephrolithiasis after MBS by 24-h urine samples and clinical questionnaires at our obesity center. Both hyperoxaluric and non-hyperoxaluric patients were screened for sequence variations in known and candidate genes implicated in hyperoxaluria (AGXT, GRHPR, HOGA1, SLC26A1, SLC26A6, SLC26A7) by targeted next generation sequencing (tNGS). The cohort comprised 67 patients, 49 females (73%) and 18 males (27%). While hyperoxaluria was found in 29 patients (43%), only one patient reported postprocedural nephrolithiasis within 41 months of follow-up. Upon tNGS, we did not find a difference regarding the burden of (rare) variants between hyperoxaluric and non-hyperoxaluric patients. However, patients with hyperoxaluria showed significantly greater weight loss accompanied by markers of intestinal malabsorption compared to non-hyperoxaluric controls. While enteric hyperoxaluria is very common after MBS, genetic variation of known hyperoxaluria genes contributes little to its pathogenesis. In contrast, the degree of postsurgical weight loss and levels of malabsorption parameters may allow for predicting the risk of enteric hyperoxaluria and consecutive kidney stone formation

Deleterious Impact of a Novel CFH Splice Site Variant in Atypical Hemolytic Uremic Syndrome

Atypical hemolytic uremic syndrome (aHUS) is a heterogeneous disorder characterized by microangiopathic hemolytic anemia (MAHA), thrombocytopenia, and acute kidney injury (AKI). In about 50% of cases, pathogenic variants in genes involved in the innate immune response including complement factors complement factor H (CFH), CFI, CFB, C3, and membrane co-factor protein (MCP/CD46) put patients at risk for uncontrolled activation of the alternative complement pathway. As aHUS is characterized by incomplete penetrance and presence of additional triggers for disease manifestation, genetic variant interpretation is challenging and streamlined functional variant evaluation is urgently needed. Here, we report the case of a 27-year-old female without previous medical and family history who presented with confusion, petechial bleeding, and anuric AKI. Kidney biopsy revealed glomerular thrombotic microangiopathy (TMA). Targeted next generation sequencing identified a paternally transmitted novel heterozygous splice site variant in the CFH gene [c.3134-2A>G; p.Asp1045_Thr1053del] which resulted in a partial in-frame deletion of exon 20 transcript as determined by cDNA analysis. On the protein level, the concomitant loss of 9 amino acids in the short consensus repeat (SCR) domains 17 and 18 of CFH includes a highly conserved cysteine residue, which is assumed to be essential for proper structural folding and protein function. Treatment with steroids, plasmapheresis, and the complement inhibitor eculizumab led to complete hematological and clinical remission after several months and stable renal function up to 6 years later. In conclusion, genetic investigation for pathogenic variants and evaluation of their functional impact, in particular in the case of splice site variants, is clinically relevant and enables not only better molecular understanding but helps to guide therapy with complement inhibitors

Magneto-optical assessment of Plasmodium parasite growth via hemozoin crystal size

Hemozoin is a natural biomarker formed during the hemoglobin metabolism of Plasmodium parasites, the causative agents of malaria. The rotating-crystal magneto-optical detection (RMOD) has been developed for its rapid and sensitive detection both in cell cultures and patient samples. In the current article we demonstrate that, besides quantifying the overall concentration of hemozoin produced by the parasites, RMOD can also track the size distribution of the hemozoin crystals. We establish the relations between the magneto-optical signal, the mean parasite age and the median crystal size throughout one erythrocytic cycle of Plasmodium falciparum parasites, where the latter two are determined by optical and scanning electron microscopy, respectively. The significant correlation between the magneto-optical signal and the stage distribution of the parasites indicates that the RMOD method can be utilized for species-specific malaria diagnosis and for the quick assessment of drug efficacy

Extended genomic HLA typing identifies previously unrecognized mismatches in living kidney transplantation

IntroductionAntibody mediated rejection (ABMR) is the most common cause of long-term allograft loss in kidney transplantation (KT). Therefore, a low human leukocyte antigen (HLA) mismatch (MM) load is favorable for KT outcomes. Hitherto, serological or low-resolution molecular HLA typing have been adapted in parallel. Here, we aimed to identify previously missed HLA mismatches and corresponding antibodies by high resolution HLA genotyping in a living-donor KT cohort.Methods103 donor/recipient pairs transplanted at the University of Leipzig Medical Center between 1998 and 2018 were re-typed using next generation sequencing (NGS) of the HLA loci -A, -B, -C, -DRB1, -DRB345, -DQA1, -DQB1, -DPA1, and -DPB1. Based on these data, we compiled HLA MM counts for each pair and comparatively evaluated genomic HLA-typing with pre-transplant obtained serological/low-resolution HLA (=one-field) typing results. NGS HLA typing (=two-field) data was further used for reclassification of de novo HLA antibodies as “donor-specific”.ResultsBy two-field HLA re-typing, we were able to identify additional MM in 64.1% (n=66) of cases for HLA loci -A, -B, -C, -DRB1 and -DQB1 that were not observed by one-field HLA typing. In patients with biopsy proven ABMR, two-field calculated MM count was significantly higher than by one-field HLA typing. For additional typed HLA loci -DRB345, -DQA1, -DPA1, and -DPB1 we observed 2, 26, 3, and 23 MM, respectively. In total, 37.3% (69/185) of de novo donor specific antibodies (DSA) formation was directed against these loci (DRB345 ➔ n=33, DQA1 ➔ n=33, DPA1 ➔ n=1, DPB1 ➔ n=10).ConclusionOur results indicate that two-field HLA typing is feasible and provides significantly more sensitive HLA MM recognition in living-donor KT. Furthermore, accurate HLA typing plays an important role in graft management as it can improve discrimination between donor and non-donor HLA directed cellular and humoral alloreactivity in the long range. The inclusion of additional HLA loci against which antibodies can be readily detected, HLA-DRB345, -DQA1, -DQB1, -DPA1, and -DPB1, will allow a more precise virtual crossmatch and better prediction of potential DSA. Furthermore, in living KT, two-field HLA typing could contribute to the selection of the immunologically most suitable donors

A non-oxidizing fabrication method for lithographic break junctions of sensitive metals

Electrochemically active metals offer advanced functionalities with respect to the well-established gold electrode arrangements in various electronic transport experiments on atomic scale objects. Such functionalities can arise from stronger interactions with the leads which provide better coupling to specific molecules and may also facilitate metallic filament formation in atomic switches. However, the higher reactivity of the electrode metal also imposes challenges in the fabrication and reliability of nanometer scale platforms, limiting the number of reported applications. Here we present a high-yield lithographic fabrication procedure suitable to extend the experimental toolkit with mechanically controllable break junctions of oxygen sensitive metallic electrodes. We fabricate and characterize silver break junctions exhibiting single-atomic conductance and superior mechanical and electrical stability at room temperature. As a proof-of-principle application, we demonstrate resistive switching between metastable few-atom configurations at finite voltage bias

Risks and benefits of ChatGPT in informing patients and families with rare kidney diseases:an explorative assessment by the European Rare Kidney Disease Reference Network (ERKNet)

Background: Rare diseases affect fewer than 1 in 2000 individuals, but approximately 150 rare kidney diseases account for about 10% of the chronic kidney disease (CKD) population, impacting millions across Europe and globally. The scarcity of medical experts for these conditions results in an unmet need for accurate and helpful patient information. Large language models like ChatGPT may offer a technological solution to assist medical professionals in educating patients and improving doctor-patient communication. We hypothesized that ChatGPT could provide accurate responses to frequently asked basic questions from patients with rare kidney diseases. Methods: Medical professionals and members of European Patient Advocacy Groups (ePAGs) affiliated with the European Rare Kidney Disease Reference Network (ERKNet) simulated patient-ChatGPT interactions using a Microsoft forms questionnaire and ChatGPT 3.5 and 4.0. Participants selected any rare kidney disease for a structured conversation with ChatGPT 3.5 or 4.0. Responses were evaluated for accuracy and helpfulness. Results: Forty-six ERKNet experts and 12 ePAGs from 13 European countries participated in this study. ChatGPT provided scientifically accurate and helpful information on 28 randomly selected rare kidney diseases, including prognostic information and genetic testing guidance. Participants expressed neutral positions regarding ChatGPT’s recommendations on alternative treatments, second opinions, and other information sources. While ChatGPT generally was perceived as helpful and empathetic, concerns about patient safety persisted. Conclusions: ChatGPT exhibited substantial potential in addressing patient inquiries regarding rare kidney diseases in a real-world context. While it demonstrated resilience against misinformation in this application, careful human oversight remains essential and indispensable.</p