Monogenic Disorders Research Articles

The most frequent febrile syndromes and autoinflammatory diseases in adulthood

Autoinflammatory diseases are characterized by inflammatory manifestations in various organ systems, whereby recurrent febrile episodes, musculoskeletal complaints, gastrointestinal and cutaneous symptoms frequently occur accompanied by serological signs of inflammation. Autoinflammatory diseases include rare monogenic entities and multifactorial or polygenic diseases, which can manifest as a variety of symptoms in the course of time. Examples of monogenic autoinflammatory diseases are familial Mediterranean fever (FMF), cryopyrin-associated periodic syndrome (CAPS), tumor necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS) and the recently described VEXAS (vacuoles, E1 enzyme, X‑linked, autoinflammatory and somatic) syndrome. For non-monogenically determined autoinflammatory diseases, the most important representatives in adulthood are adult-onset Still's disease (AOSD) and the Schnitzler syndrome, in which a polygenic susceptibility and epigenetic factors are more likely to play a role.

The Protective Role of KANK1 in Podocyte Injury.

Approximately 30% of steroid-resistant nephrotic syndromes are attributed to monogenic disorders that involve 27 genes. Mutations in KANK family members have also been linked to nephrotic syndrome; however, the precise mechanism remains elusive. To investigate this, podocyte-specific Kank1 knockout mice were generated to examine phenotypic changes. In the initial assessment under normal conditions, Kank1 knockout mice showed no significant differences in the urinary albumin-creatinine ratio, blood urea nitrogen, serum creatinine levels, or histological features compared to controls. However, following kidney injury with adriamycin, podocyte-specific Kank1 knockout mice exhibited a significantly higher albumin-creatinine ratio and a significantly greater sclerotic index than control mice. Electron microscopy revealed more extensive foot process effacement in the knockout mice than in control mice. In addition, KANK1-deficient human podocytes showed increased detachment and apoptosis following adriamycin exposure. These findings suggest that KANK1 may play a protective role in mitigating podocyte damage under pathological conditions.

Focused Ultrasound-Mediated Disruption of the Blood-Brain Barrier for AAV9 Delivery in a Mouse Model of Huntington's Disease.

Huntington's disease (HD) is a monogenic neurodegenerative disorder caused by a cytosine-adenine-guanine (CAG) trinucleotide repeat expansion in the HTT gene. There are no cures for HD, but the genetic basis of this disorder makes gene therapy a viable approach. Adeno-associated virus (AAV)-miRNA-based therapies have been demonstrated to be effective in lowering HTT mRNA; however, the blood-brain barrier (BBB) poses a significant challenge for gene delivery to the brain. Delivery strategies include direct injections into the central nervous system, which are invasive and can result in poor diffusion of viral particles through the brain parenchyma. Focused ultrasound (FUS) is an alternative approach that can be used to non-invasively deliver AAVs by temporarily disrupting the BBB. Here, we investigate FUS-mediated delivery of a single-stranded AAV9 bearing a cDNA for GFP in 2-month-old wild-type mice and the zQ175 HD mouse model at 2-, 6-, and 12-months. FUS treatment improved AAV9 delivery for all mouse groups. The delivery efficacy was similar for all WT and HD groups, with the exception of the zQ175 12-month cohort, where we observed decreased GFP expression. Astrocytosis did not increase after FUS treatment, even within the zQ175 12-month group exhibiting higher baseline levels of GFAP expression. These findings demonstrate that FUS can be used to non-invasively deliver an AAV9-based gene therapy to targeted brain regions in a mouse model of Huntington's disease.

Objectivizing issues in the diagnosis of complex rare diseases: lessons learned from testing existing diagnosis support systems on ciliopathies

BackgroundThere are approximately 8,000 different rare diseases that affect roughly 400 million people worldwide. Many of them suffer from delayed diagnosis. Ciliopathies are rare monogenic disorders characterized by a significant phenotypic and genetic heterogeneity that raises an important challenge for clinical diagnosis. Diagnosis support systems (DSS) applied to electronic health record (EHR) data may help identify undiagnosed patients, which is of paramount importance to improve patients’ care. Our objective was to evaluate three online-accessible rare disease DSSs using phenotypes derived from EHRs for the diagnosis of ciliopathies.MethodsTwo datasets of ciliopathy cases, either proven or suspected, and two datasets of controls were used to evaluate the DSSs. Patient phenotypes were automatically extracted from their EHRs and converted to Human Phenotype Ontology terms. We tested the ability of the DSSs to diagnose cases in contrast to controls based on Orphanet ontology.ResultsA total of 79 cases and 38 controls were selected. Performances of the DSSs on ciliopathy real world data (best DSS with area under the ROC curve = 0.72) were not as good as published performances on the test set used in the DSS development phase. None of these systems obtained results which could be described as “expert-level”. Patients with multisystemic symptoms were generally easier to diagnose than patients with isolated symptoms. Diseases easily confused with ciliopathy generally affected multiple organs and had overlapping phenotypes. Four challenges need to be considered to improve the performances: to make the DSSs interoperable with EHR systems, to validate the performances in real-life settings, to deal with data quality, and to leverage methods and resources for rare and complex diseases.ConclusionOur study provides insights into the complexities of diagnosing highly heterogenous rare diseases and offers lessons derived from evaluation existing DSSs in real-world settings. These insights are not only beneficial for ciliopathy diagnosis but also hold relevance for the enhancement of DSS for various complex rare disorders, by guiding the development of more clinically relevant rare disease DSSs, that could support early diagnosis and finally make more patients eligible for treatment.

#2045 Epigenetic data can predict initial treatment response in nephrotic syndrome

Abstract Background and Aims The majority of children with idiopathic nephrotic syndrome (INS) and adults with Focal Segmental Glomerulosclerosis (FSGS) and Minimal Change Disease (MCD) receive glucocorticoid treatment at diagnosis. Only those with a high likelihood of having monogenic disease or a contraindication to steroids might avoid this treatment. About 10% overall will not respond to steroids and we have no reliable way of prospectively identifying these patients. Therefore, some patients will receive a futile treatment which is accompanied by significant side effects. DNA methylation (DNAm) is an epigenetic mechanism meaning that it can induce stable but reversible changes in gene expression without any change in underlying DNA sequence. DNAm has shown great potential as a treatment stratification tool, for example, DNAm data is used in oncology to identify which patients are likely to benefit from alkylating chemotherapy. We investigated whether DNAm can predict initial response to steroids in children and young adults with nephrotic syndrome. Method Three hundred and seventeen patients with INS were selected from the NephroS and NURTuRE cohorts. All patients were diagnosed with INS ≤ 30 years of age and those who underwent a renal biopsy had a histological diagnosis of either FSGS or MCD. Peripheral blood DNAm measurements were generated using the Illumina MethylationEPIC Beadchip (>850, 000 CpG sites). Clinical data was used to label patients by their initial response to steroids (sensitive, n = 156, or resistant, n = 161). Machine learning models were created to predict steroid response from the DNAm data. Models were generated using elastic net following feature filtering, and model hyperparameters were tuned and performance measured within the context of cross validation. To exclude whether cumulative steroid exposure prior to sample collection had impacted our results, the CpG sites in the final model were compared to those identified in a published study examining steroid exposure and DNAm (4). Results The 317 INS patients had a median age at diagnosis of 5 years (IQR 2-10) and a median time between diagnosis and DNAm sample collection of 4 years (IQR 1-10). The steroid resistant group were made up of patients with known monogenic disease (n = 75, 24%) and those without pathogenic variants (n = 86, 27%). Initial response to steroid treatment could be predicted with 65% accuracy and an area under the curve (AUC) of 0.75, (sensitivity 0.65, specificity of 0.66, see Fig. 1) using DNAm levels at 14 CpG sites. There was no overlap between the 14 CpG sites in our prediction model and those that are known to alter with steroid treatment. Conclusion We have demonstrated that peripheral blood cell DNAm profiles are a promising predictor of steroid response in INS. Further work to incorporate genetic data into the prediction models is underway and external validation of the results in a separate cohort of patients is required.

#2259 Preimplantation genetic testing in inherited kidney diseases

Abstract Background and Aims Identifying the underlying genetic cause in individuals with monogenic kidney disease allow counselling to provide prognosis and therapeutic options. In addition, discussions may extend to assessing the risk of having affected children and exploring family planning alternatives. Pre-conception counselling covers a wide range of considerations, including the expected pregnancy outcome for both mother and child, the risk of recurrence, invasive prenatal diagnosis, and the option of pre-implantation genetic testing (PGT). In this study we provide a clinical overview of PGT for monogenic kidney disease in our centre. Methods This is a retrospective cohort study of individuals with monogenic kidney disease counselled on our fertility clinic for PGT, in the Fundació Puigvert—Hospital de Sant Pau, Barcelona-Spain from January 2016 to 2023. Results During the study period, 751 visits were made to the fertility clinic, of which 8.3% (63/751) had a monogenic inherited kidney disease (IKD). Regarding the baseline characteristics of individuals with monogenic conditions, most were females (70%; 44/63). The mean age of the women was 33 years, most had no history of pregnancy prior to the first visit (73%). The mean anti-Mullerian hormone (AMH) level was 2.67 ng/ml, with 22% having levels below 1.1 ng/ml. Most cases (84%; 53/63) showed an autosomal dominant pattern of inheritance, with autosomal dominant polycystic kidney disease (ADPKD) being the primary cause in 66% of cases (42/63), followed by tuberous sclerosis complex in 8% (5/63). Autosomal recessive and X-linked disorders were each present in 8% (5/63). Table 1 shows the complete list of genetic kidney disease cases that consulted the fertility clinic. In terms of renal function, affected women had a mean renal function measured by estimated glomerular filtration rate (eGFR) of 90 mil/min/1.73 m2, with 74% having chronic kidney disease (CKD) category G1. Affected male had mean eGFR of 65 mL/min/1.73 m2, with only 38% (6/19 patients) having CKD-G1. Two (13%; 2/19) of the affected men had received a kidney transplant. Of the 63 couples who were counseled, 51% (32/63) agreed to proceed with PGT; 81% (26/32) underwent at least one cycle of ovarian stimulation, in vitro fertilization, and PGT. Fifty per cent (13/26) had a live birth child and 19% (5/26) are currently pregnant. Six couples (10%; 6/32) have pending tests. Among patients who decided not to proceed with PGT (31/63), the main reason for not doing so was that they had a spontaneous pregnancy before the first PGT cycle (35%; 11/31). Low ovarian reserve and couple´s refusal to proceed with PGT were the second most common reasons, each accounting for 22.5% of cases. In 10% (3/31) of cases, the indication for PGT was not yet approved in Spain (mainly because these patients already had a healthy living child). Maternal age over 40 years and the age of the prospective father were the reasons for not performing PGT in 6% and 3% respectively. Of note, a patient with ADPKD presented with a ruptured hepatic cyst after ovarian hormone stimulation. Therefore, PGT was discontinued after two cycles. Conclusion Women with IKD are most likely to request PGT than affected males. The most frequent condition is, by far, ADPKD. Once the technique is explained less than 50% of couples keep wishing to undergo PGT. Low ovarian reserve (which correlates quite well with age) is an important reason that impedes to go through PGT. Larger international studies are needed to understand the patient's uptake of PGT for IKD as well as the access to this technique depending on the country.

#1049 Genetic characteristics of autosomal dominant polycystic kidney disease in a Greek population

Abstract Background and Aims Autosomal dominant polycystic kidney disease (ADPKD) is the predominant monogenic renal genetic disorder, and the fourth leading cause of end stage kidney disease. Confirmatory genetic testing defines the disease, provides prognostic information and may support therapeutic management. This study aims to investigate the genetic characteristics of a substantial cohort of ADPKD patients from a single Greek center. Method Ninety-three patients (46 females, 47 males with a mean age of 34 ± 15 years) were enrolled from 59 distinct families attending the outpatient ADPKD clinic at the Nephrology Department of the General Hospital of Athens “G. Gennimatas.” Genetic analysis included targeted next-generation sequencing (tNGS) of over 600 clinically relevant genes, Sanger sequencing, and Multiplex ligation-dependent probe amplification (MLPA). Whole exome and whole genome sequencing (WES and WGS) studies were conducted in 3 patients with negative results. Magnetic Resonance Imaging (MRI) was performed in 74 out of 93 patients, revealing more than 10 renal cysts in all but one patient. Children with a positive family history (FH) displayed at least one cyst in echography, while two without FH had multiple renal cysts. Results Genetic diagnosis was established in 88 of 93 patients (94.5%). Seventy patients (75%), demonstrated single nucleotide variants (SNVs) and large deletions (4 patients) in the PKD1 gene, whereas SNVs and large deletions (5 patients) in the PKD2 gene were identified in 15 (16%) patients. Additionally, mutations in genes other than PKD1 and PKD2 were identified in 3 patients (3.5%). Two cases, involving a father and son, revealed the presence of a SEC61B variant; the father exhibited more than 10 renal cysts and liver cysts in the MRI, while the son displayed only liver cysts. Additionally, a third patient, a woman with nephrolithiasis and over 10 renal cysts in the MRI, exhibited a SLC3A1 variant. Notably, 5 patients (5.5%) with ADPKD phenotype had negative genetic analyses, despite the application of both WES and WGS in three of these patients. Truncating mutations in PKD1 were observed in 43 of 70 cases, (61%), while the rest (39%) had non-truncating mutations. Detected variants were classified as Pathogenic (45.5%), Likely Pathogenic (36%), and Variants of Uncertain Significance (VUS-13.5%, 12 cases), according to the guidelines of the American College of Medical Genetics and Genomics. Reclassification to Likely Pathogenic could be proposed for 6 out of 12 cases with VUS variants for which family segregation was noted. Finally, 52% and 82% of the detected variants have not been previously reported in ClinVar and gnomAD databases, respectively. Conclusion In this ethnically homogenous population, truncating mutations in the PKD1 gene were the predominant genetic cause of ADPKD, followed by PKD1 non-truncating mutations, PKD2 gene variants and other rare or undefined genetic etiologies.

#787 Kidney genetics—a reproducible and curated database of kidney-disease associated genes

Abstract Background and Aims Genetic insights are becoming increasingly influential in the understanding and treatment of various kidney diseases (KD). Hundreds of genes associated with monogenic kidney disease have been identified, providing valuable insights into their diagnosis, management, and monitoring. However, the lack of a unified and standardized database of genes assigned to kidney diseases has led to diagnostic blind spots and comparability issues among current studies of kidney genetics. To address this gap, we created “Kidney-Genetics”, a regularly updated, automated and publicly accessible database, which aims to provide a comprehensive list of all relevant genes associated with kidney disease. Methods Kidney disease-associated gene information was compiled from various sources, including: (1) Genomics England and Australia PanelApp [1], (2) a comprehensive literature review of published gene lists, (3) clinical diagnostic panels for kidney disease, (4) a Human Phenotype Ontology (HPO)-based [2] search in rare disease databases (OMIM, Orphanet), and (5) a PubTator [3] API-based automated literature extraction from PubMed. An evidence-scoring system was developed to distinguish high- evidence genes from low evidence genes and candidate genes. High-evidence genes were defined as those present in two or more of the five resources and were manually curated based on predetermined criteria or, in the case of existing ClinGen [4] curation, their data and scores were used. Genes with a score of one or less were accordingly classified as candidate genes. Additionally, genes were grouped into different categories for later genotype-phenotype correlation matching (see Fig. 1). Results The Kidney-Genetics database currently contains detailed information on 3025 kidney-associated genes with detailed annotations on gene expression, kidney phenotype, inheritance mode, disease onset, possible syndromic disease mode and genetic variation. The number of genes extracted from the five analyzed sources of information are as follows: (1) 534, (2) 822, (3) 956, (4) 789, and (5) 2158 (see Fig. 2). Notably, 598 genes (19.8%) of the total 3025 genes are present in two or more of the analyzed information sources, thus meeting our evidence criteria, indicating high confidence and their potential for diagnostic use. Of these high-evidence genes, 526 (88.0%) are present in at least one, and 56 (9.4%) are present in all 10 comprehensive diagnostic laboratory panels. To ensure currency, Kidney-Genetics will be updated regularly and automatically on a monthly basis. We will also provide phenotypic and functional clustering results to facilitate gene grouping. Conclusion By utilizing Kidney-Genetics, clinicians, geneticists, and researchers can examine genomic data and improve their understanding of the genetic components of diverse KDs. The code and results are freely available on GitHub (kidney-genetics.org) [5]. A standardized pipeline and automated system keep our database on the cutting edge of kidney research and diagnostics. Screening efforts toward manual curation (such as through the ClinGen initiative) and assignment of diagnostic genes to kidney disease groups (e.g., syndromic vs. isolated; adult vs. pediatric; cystic, nephrotic, etc.) are currently under development.

#1012 Lifetime risk of autosomal recessive kidney diseases calculated from genetic databases

Abstract Background and Aims Genetic kidney diseases represent an often rare and clinically diverse group. Their distinct clinical and genetic variations and biases in patient referrals and identification pose challenges in phenotype-based estimated prevalences. This study aimed to determine the calculated lifetime risk of autosomal recessive kidney diseases. Method We conducted a thorough literature review to compile a list of 149 genes linked to these diseases. Disease-causing variants were collected from ClinVar, HGMD, LOVD, and our database and reevaluated according to current guidelines. Minor allele frequencies were obtained from gnomAD and our database. We estimated the lifetime risk of autosomal recessive kidney diseases in a dataset of 12,800 disease-causing variants across 149 disease-associated genes (31 glomerulopathy, 16 tubulopathy, 87 ciliopathy, and 15 CAKUT genes). Results The combined estimated lifetime risk is 10.68 per 100,000 (95% confidence interval 6.29-18.40) based on our data and 22.77 per 100,000 (15.86-33.77) using the European gnomAD dataset. Notably, the three disorders with the highest lifetime risk (≥1.2 per 100,000), collectively accounting for 28% of the overall lifetime risk, were caused by PKHD1 (autosomal recessive polycystic kidney disease), SLC12A3 (Gitelman syndrome), and COL4A3 (Alport syndrome) variants (Fig. 1). Extrapolation to all modes of inheritance, the overall lifetime risk for monogenic kidney disease in adults ranged from 1 in 602 to 1 in 1,283 (Fig. 2). Conclusion This study provides a population-genetic estimate of lifetime risk for autosomal recessive kidney diseases across different populations, addressing underestimated prevalences and diagnostic probabilities. The data, therefore, informs resource allocation for therapy development, public health management, and biomedical research.

#276 ADTKD genetic diagnostics in Europe: where do we stand and what is needed?

Abstract Background and Aims We are the first European patient organization to pursue the goal of raising awareness of the monogenic kidney disease ADTKD (autosomal dominant tubulointerstitial kidney disease) and supporting its research (www.adtkd.de/en-gb). To date, causative mutations are known in at least five disease genes (UMOD, MUC1, REN, HNF1B, SEC61A1) [1] and one can expect that even more disease genes exist. There are already strong international collaborations to define the clinical course of ADTKD [2] and to evaluate a targeted therapy in clinical trials [3]. Clinical registries form the basis for the inclusion of patients, preferably at an early stage of the disease. Such a registry already exists in the USA and is currently being established in Europe (ADTKD-Net) as part of the European Joint Program on Rare Diseases (EJP RD). Due to its non-specific and variable clinical characteristics, ADTKD is often misdiagnosed or not diagnosed at all. Experts therefore suspect a high number of unreported cases. There are also challenges in genetic diagnostics. While next generation sequencing (NGS) panels have been established for ADTKD, they are usually unable to detect pathogenic MUC1 variants due to their specific location in the genome. This is the insertion of an additional cytosine (dupC) in a VNTR (Variable Number of Tandem Repeats) domain of the MUC1 gene, which cannot be detected by NGS and therefore requires special procedures such as SnaPshot Minisequencing [4] or VNtyper [5]. For instance, there are only two laboratories that can perform this specific MUC1 testing in Germany to date. The aim of this study is to assess the status quo of ADTKD diagnostics in Europe. We hypothesize that there is a lack of appropriate structures to adequately and reliably diagnose ADTKD, notably ADTKD-MUC1. The study is intended to help identify deficits and obstacles in order to address these in a targeted manner. Methods We used Survey Monkey to create a digital survey, which we sent by email to around 50 European ADTKD experts. They were asked to answer 7 key questions (Fig. 1). For the selection of suitable ADTKD experts, we use various sources such as publications on ADTKD in PubMed, the Expert Finder and the European Patient Advocacy Groups (ePAG) in the European Reference Network for Rare Kidney Diseases (ERKNet) and our own network. Our aim is to cover at least the 30 largest countries in Europe in terms of population. Results Results will be presented at the ERA conference. Conclusion With our survey we would like to substantiate the hypothesis that the possibilities of molecular diagnostics of ADTKD in Europe are currently insufficient. Based on our results, short and long-term measures should be taken to remedy potential deficits so that as many patients as possible can be identified and have access to therapeutic options in the future. Another interesting aspect is the awareness of ADTKD among European nephrologists. This could be a future activity of our patient organization.

Large-scale mutational analysis identifies UNC93B1 variants that drive TLR-mediated autoimmunity in mice and humans.

Nucleic acid-sensing Toll-like receptors (TLR) 3, 7/8, and 9 are key innate immune sensors whose activities must be tightly regulated to prevent systemic autoimmune or autoinflammatory disease or virus-associated immunopathology. Here, we report a systematic scanning-alanine mutagenesis screen of all cytosolic and luminal residues of the TLR chaperone protein UNC93B1, which identified both negative and positive regulatory regions affecting TLR3, TLR7, and TLR9 responses. We subsequently identified two families harboring heterozygous coding mutations in UNC93B1, UNC93B1+/T93I and UNC93B1+/R336C, both in key negative regulatory regions identified in our screen. These patients presented with cutaneous tumid lupus and juvenile idiopathic arthritis plus neuroinflammatory disease, respectively. Disruption of UNC93B1-mediated regulation by these mutations led to enhanced TLR7/8 responses, and both variants resulted in systemic autoimmune or inflammatory disease when introduced into mice via genome editing. Altogether, our results implicate the UNC93B1-TLR7/8 axis in human monogenic autoimmune diseases and provide a functional resource to assess the impact of yet-to-be-reported UNC93B1 mutations.

#1790 Metformin versus standard of care in slowing progression of autosomal dominant polycystic kidney disease and correlation with total kidney volume

Abstract Background and Aims Autosomal dominant kidney disease (ADPKD) is the most common monogenic disorder leading to renal failure with very limited therapeutic options. Apart from lifestyle modifications and control of hypertension, tolvaptan is the only Food and Drug Administration (FDA) approved disease modifying drug. Although, it has proven therapeutic benefit in slowing disease progression in high risk Mayo Class (Mayo Class 1C-E), the aquaretic potential, potential hepatotoxicity and the cost limits its widespread use especially in resource constrained country. Metformin has been shown to be effective in ADPKD in preclinical studies and is also well tolerated by the general population. We planned this study to assess the efficacy and safety of metformin in non diabetic ADPKD patients. Method Our study is a prospective, randomized controlled, open labelled clinical trial of 52 non diabetic adults 18 to 60 years of age with typical ADPKD, estimated glomerular filtration rate (eGFR) > 45 ml/min/m2 and no risk factors of rapid progression. Participants were randomized in a 1:1 ratio by a computer-generated random number table into Metformin + standard of care group (Metformin arm) and standard of care group (Placebo arm). Primary outcome of the study was to evaluate the effects of metformin versus placebo arm on the percentage and absolute change in eGFR over 6-month period. Secondary outcomes were to study the effect of metformin versus placebo arm on the percentage and absolute change in height adjusted total kidney volume (htTKV ml/m) at 6 months, to evaluate the effect of baseline plasma copeptin levels with percentage change in htTKV and eGFR over 6 months, to evaluate metformin tolerability, to evaluate the effects of metformin versus placebo on the changes in body weight, BMI, blood pressure and urine protein excretion at 6 months period. Results Mean (SD) age of the cohort was 37.15 (10.16) years with half of them being females. The mean (SD) baseline htTKV and eGFR was 335.67 (153.3) ml/m and 100.23 (25.95) ml/min/m2. Clinical exome sequencing was available in 9 (17.3%) patients of which two third had PKD1 mutation. Baseline characteristics were distributed equally across randomized groups. Baseline proteinuria was significantly higher in the Metformin arm (p = 0.014). The eGFR difference and percentage change in eGFR was not different between the groups at 6 months (p = 0.535, 0.483). There was no statistically significant difference in htTKV difference and percentage change in htTKV at 6 months between the groups although increase in htTKV was numerically smaller in the metformin group (p = 0.769, 0.805). Blood pressure, weight, body mass index (BMI) and proteinuria also did not differ between two groups. Half of the cohort tolerated the maximum dose of metformin. Around 2/3rd patients reported adverse effects most commonly asthenia. There was no lactic acidosis or significant gastrointestinal side effects as assessed by gastrointestinal rating scale (GSRS) scale. Baseline copeptin levels did not correlate with eGFR or htTKV difference at 6 months. Conclusion Metformin appears to be safe and tolerable in non diabetic ADPKD patients over 6 months. However larger clinical trials are needed to conclude regarding the efficacy in terms of eGFR decline or htTKV progression.

#1315 Management and long-term outcome of recurrent idiopathic FSGS in pediatric renal transplant recipients

Abstract Background and Aims Focal segmental glomerulosclerosis (FSGS) is a leading cause of pediatric end-stage renal disease (ESRD). While approximately 30% of pediatric FSGS is attributed to monogenic disorders, most cases are idiopathic, carrying a high risk of post-transplantation recurrence and graft loss. Commonly used protocols for recurrent FSGS (rFSGS) include plasmapheresis or immunoadsorption, and/or immunomodulatory therapy. We retrospectively evaluated the efficacy and safety of early plasmapheresis followed by rituximab therapy for induction of remission in rFSGS. Method Between 2014-2023, 8/65 pediatric renal transplant recipients at our center were diagnosed with idiopathic FSGS. Five patients underwent preventive plasmapheresis initiated between day 7 pre-transplantation to day 1 post-transplantation, depending on donor source (living/deceased). rFSGS, was diagnosed based on nephrotic range proteinuria of no other cause, and managed with daily plasmapheresis, followed by frequency tapering. Failure to achieve complete remission while on prolonged plasmapheresis was managed with Rituximab therapy. Results 6/8 patients (75%) experienced rFSGS. All achieved partial or complete remission with plasmapheresis therapy. Nevertheless, 5/6 patients exhibited plasmapheresis-dependence, thereby necessitating rituximab therapy. Of these, 3/5 patients achieved sustained remission enabling plasmapheresis cessation, while in 2/5 showed markedly improved proteinuria, enabling reduction of plasmapheresis frequency to once weekly. Adverse effects included rituximab-induced serum sickness in one patient, requiring therapy discontinuation. While one patient suffered from graft loss due to humoral rejection, no graft was lost to rFSGS, and all other grafts remained functional over an average follow-up period of 50 months. Conclusion We suggest that early introduction of plasmapheresis and rituximab therapy effectively induces remission in most post-transplantation rFSGS, is well tolerated, and prevents graft loss. Additional, large scale studies are needed to establish our observation.

Prenatal Diagnosis of Cystic Fibrosis by Celocentesis.

Celocentesis is a new sampling tool for prenatal diagnosis available from 7 weeks in case of couples at risk for genetic diseases. In this study, we reported the feasibility of earlier prenatal diagnosis by celocentesis in four cases of cystic fibrosis and one case of cystic fibrosis and β-thalassemia co-inherited in the same fetus. Celomic fluids were aspired from the celomic cavity between 8+2 and 9+3 weeks of gestation and fetal cells were picked up by micromanipulator. Maternal DNA contamination was tested and target regions of fetal DNA containing parental pathogenetic variants of CFTR and HBB genes were amplified and sequenced. Four of the five fetuses resulted as being affected by cystic fibrosis and, in all cases, the women decided to interrupt the pregnancy. In the other case, the fetus presented a healthy carrier of cystic fibrosis. The results were confirmed in three cases on placental tissue. In one case, no abortive tissue was obtained. In the last case, the woman refused the prenatal diagnosis to confirm the celocentesis data; the pregnancy is ongoing without complications. This procedure provides prenatal diagnosis of monogenic diseases at least four weeks earlier than traditional procedures, reducing the anxiety of patients and providing the option for medical termination of the affected fetus at 8-10 weeks of gestation, which is less traumatic and safer than surgical termination in the second trimester.

#2160 Ketosis moderates the effect on kidney volume in dietary interventions for ADPKD—more insights on the KETO ADPKD trial

Abstract Background and Aims Autosomal-dominant polycystic kidney disease (ADPKD) is the most common monogenic disease leading to kidney failure. Tolvaptan, the only approved targeted treatment strategy, comes with adverse events such as hepatotoxicity and massive polyuria, limiting its use. Novel treatment strategies are urgently needed. Cyst-lining epithelial cells are glucose-dependent and metabolically inflexible. Evidence from polycystic kidney disease (PKD) animal models show that ketogenic dietary interventions (KDI) can ameliorate cyst growth and loss of kidney function. To enable clinical translation of these findings, our group set up a series of trials—from small cohorts and proof of principle studies to our most recent trial KETO-ADPKD, showing that KDIs are feasible and can work as a treatment for ADPKD [1]. This has received a lot of attention. With this post-hoc analyses, we aim to share further in-depth analyses of the factors moderating the effects we see on ADPKD. Method KETO-ADPKD is an exploratory randomized and controlled clinical trial (NCT04680780). Sixty-six patients were randomized to 3 months dietary intervention (ketogenic diet [KD] or water fasting [WF]) or the control group. Here, we explore correlations between biochemical readout parameters of ketosis and markers of disease progression. Results The KD group shows a promising, yet statistically not significant decline in height-adjusted total kidney volume (htTKV). Patients reaching high biochemical thresholds of ketosis however significantly reduced their htTKV in comparison with the control group (KD −16.3 ml/m, CG + 14.8 ml/m, p-value 0.049). This becomes even clearer when higher thresholds for adherence are administered: In a smaller group requiring not only beta-hydroxybutyrate (BHB) levels ≥0.5 mmol/l but breath acetone ≥5 ppm on 75% of daily measurements, htTKV could be reduced by −17.6 ml/m (KD) vs +14.8 ml/m (CG), p-value 0.026. The significant reduction of liver volume upon KD is not influenced by the level of ketosis. Beneficial effects on estimated glomerular filtration rate (eGFR) can be equally observed in all subsets. Weight loss ≥5% was nor associated with a more significant loss of kidney nor liver volume. Conclusion Subgroup analyses of the KETO-ADPKD trial show stronger impact of the dietary intervention with higher ketone body levels. In particular, ketogenesis as a marker of metabolic reprogramming strongly moderates the effects we see on kidney volume. The assessment of renal cyst fractions could further enlighten the effects on cyst burden. This is in line with preclinical data showing that ketosis rather than caloric intake is responsible for the amelioration of disease progression [2].

Comprehensive analysis of thalassemia alleles (CATSA) based on third-generation sequencing is a comprehensive and accurate approach for neonatal thalassemia screening

Thalassemia is one of the most common and damaging monogenic diseases in the world. It is caused by pathogenic variants of α- and/or β-globin genes, which disrupt the balance of these two protein chains and leads to α-thalassemia or β-thalassemia, respectively. Patients with α-thalassemia or β-thalassemia could exhibit a severe phenotype, with no simple and effective treatment. A three-tiered strategy of carrier screening, prenatal diagnosis and newborn screening has been established in China for the prevention and control of thalassemia, of which the first two parts have been studied thoroughly. The implementation of neonatal thalassemia screening is lagging, and the effectiveness of various screening programs has not yet been demonstrated. In this study, hemoglobin capillary electrophoresis (CE), hotspot testing method, and third-generation sequencing (TGS) were used in the variant detection of 2000 newborn samples, to assess the efficacy of these methods in neonatal thalassemia screening. Compared with CE (249, 12.45 %) and hotspot analysis (424, 21.2 %), CATSA detected the largest number of thalassemia variants (535, 26.75 %), which included 24 hotspot variants, increased copy number of α-globin gene, rare pathogenic variants, and three unreported potentially disease-causing variants. More importantly, CATSA directly determined the cis–trans relationship of variants in three newborns, which greatly shortens the clinical diagnosis time of thalassemia. CATSA showed a great advantage over other genetic tests and could become the most powerful technical support for the three-tiered prevention and control strategy of thalassemia.

Mechanisms of synapse-to-nucleus calcium signalling in striatal neurons and impairments in Huntington's disease.

Huntington's disease (HD) is a monogenic disorder with autosomal dominant inheritance. In HD patients, neurons in the striatum and cortex degenerate, leading to motor, psychiatric and cognitive disorders. Dysregulated synaptic function and calcium handling are common in many neurodegenerative diseases, including HD. N-methyl-D-aspartate (NMDA) receptor function is enhanced in HD at extrasynaptic sites, altering the balance of calcium-dependent neuronal survival versus death signalling pathways. Endoplasmic reticulum (ER) calcium handling is also abnormal in HD. The ER, which is continuous with the nuclear envelope, is purportedly involved in nuclear calcium signalling; based on this, we hypothesised that nuclear calcium signalling is altered in HD. We explored this hypothesis with calcium imaging techniques, including simultaneous epifluorescent imaging of cytosolic and nuclear calcium using jRCaMP1b and GCaMP3 sensors, respectively, in striatal spiny projection neurons in cortical-striatal co-cultures from the YAC128 mouse model of HD. Our data show contributions from a variety of calcium channels to nuclear calcium signalling. NMDA receptors (NMDARs) play an essential role in initiating action potential-dependent calcium signalling to the nucleus, and ryanodine receptors (RyR) contribute to both cytosolic and nuclear calcium signals. Unlike previous reports in glutamatergic hippocampal and cortical neurons, we found that in GABAergic striatal neurons, L-type voltage-gated calcium channels (CaV) contribute to cytosolic, but not nuclear calcium signalling. Calcium imaging also suggests impairments in nuclear calcium signalling in HD striatal neurons, where spontaneous action potential-dependent calcium transients in the nucleus were smaller in YAC128 striatal neurons compared to those of wild-type (WT). Our results elucidate mechanisms involved in action potential-dependent nuclear calcium signalling in GABAergic striatal neurons, and have revealed a clear deficit in this signalling in HD.

Gene Therapy for Neurofibromatosis Type2-Related Schwannomatosis: Recent Progress, Challenges, and Future Directions.

Neurofibromatosis type2 (NF2)-related schwannomatosis is a rare autosomal dominant monogenic disorder caused by mutations in the NF2 gene. The hallmarks of NF2-related schwannomatosis are bilateral vestibular schwannomas (VS). The current treatment options for NF2-related schwannomatosis, such as observation with serial imaging, surgery, radiotherapy, and pharmacotherapies, have shown limited effectiveness and serious complications. Therefore, there is a critical demand for novel effective treatments. Gene therapy, which has made significant advancements in treating genetic diseases, holds promise for the treatment of this disease. This review covers the genetic pathogenesis of NF2-related schwannomatosis, the latest progress in gene therapy strategies, current challenges, and future directions of gene therapy for NF2-related schwannomatosis.

A heatmap for expected cumulative live birth rate in preimplantation genetic testing for monogenic disorders and chromosomal structural rearrangements

PurposeOur objective is to predict the cumulative live birth rate (CLBR) and identify the specific subset within the population undergoing preimplantation genetic testing for monogenic disorders (PGT-M) and chromosomal structural rearrangements (PGT-SR) which is likely to exhibit a diminished expected CLBR based on various patient demographics.MethodsWe performed a single-centre retrospective cohort study including 1522 women undergoing 3130 PGT cycles at a referral centre for PGT. A logistic regression analysis was performed to predict the CLBR per ovarian stimulation in women undergoing PGT-M by polymerase chain reaction (PCR) or single-nucleotide polymorphism (SNP) array, and in women undergoing PGT-SR by SNP array, array comparative genomic hybridization (CGH) or next-generation sequencing (NGS).ResultsThe mean age of women was 32.6 years, with a mean AMH of 2.75 µg/L. Female age and AMH significantly affected the expected CLBR irrespective of the inheritance mode or PGT technology. An expected CLBR < 10% was reached above the age of 42 years and AMH ≤ 1.25 µg/L. We found no significant difference in outcome per ovarian stimulation between the different PGT technologies, i.e. PCR, SNP array, array CGH and NGS. Whereas per embryo transfer, we noticed a significantly higher probability of live birth when SNP array, array CGH and NGS were used as compared to PCR.ConclusionIn a PGT-setting, couples with an unfavourable female age and AMH should be informed of the prognosis to allow other reproductive choices. The heatmap produced in this study can be used as a visual tool for PGT couples.

Familial communication and cascade testing following elective genomic testing.

Familial communication of results and cascade genetic testing (CGT) can extend the benefits of genetic screening beyond the patient to their at-risk relatives. While an increasing number of health systems are offering genetic screening as an elective clinical service, data are limited about how often results are shared and how often results lead to CGT. From 2018 to 2022, the Sanford Health system offered the Sanford Chip, an elective genomic test that included screening for medically actionable predispositions for disease recommended by the American College of Medical Genetics and Genomics for secondary findings disclosure, to its adult primary care patients. We analyzed patient-reported data about familial sharing of results and CGT among patients who received Sanford Chip results at least 1 year previously. Among the patients identified with medically actionable predispositions, 94.6% (53/56) reported disclosing their result to at least one family member, compared with 46.7% (423/906) of patients with uninformative findings (p < 0.001). Of the patients with actionable predispositions, 52.2% (12/23) with a monogenic disease risk and 12.1% (4/33) with a carrier status reported that their relatives underwent CGT. Results suggest that while the identification of monogenic risk during elective genomic testing motivates CGT in many at-risk relatives, there remain untested at-risk relatives who may benefit from future CGT. Findings identify an area that may benefit from increased genetic counseling and the development of tools and resources to encourage CGT for family members.