Genetic Markers Among the Israeli Druze Minority Population With End-Stage Kidney Disease.

RATIONALE & OBJECTIVE: Genetic etiologies have been identified among approximately 10% of adults with chronic kidney disease (CKD). However, data are lacking regarding the prevalence of monogenic etiologies especially among members of minority groups. This study characterized the genetic markers among members of an Israeli minority group with end-stage kidney disease (ESKD). STUDY DESIGN: A national-multicenter cross-sectional study of Israeli Druze patients (an Arabic-speaking Near-Eastern transnational population isolate) who are receiving maintenance dialysis for ESKD. All study participants underwent exome sequencing. SETTING & PARTICIPANTS: We recruited 94 adults with ESKD, comprising 97% of the total 97 Druze individuals throughout Israel being treated with dialysis during the study period. PREDICTORS: Demographics and clinical characteristics of kidney disease. OUTCOME: Genetic markers. ANALYTICAL APPROACH: Whole-exome sequencing and the relationship of markers to clinical phenotypes. RESULTS: We identified genetic etiologies in 17 of 94 participants (18%). None had a previous molecular diagnosis. A novel, population-specific, WDR19 homozygous pathogenic variant (p.Cys293Tyr) was the most common genetic finding. Other monogenic etiologies included PKD1, PKD2, type IV collagen mutations, and monogenic forms of noncommunicable diseases. The pre-exome clinical diagnosis corresponded to the final molecular diagnosis in fewer than half of the participants. LIMITATIONS: This study was limited to Druze individuals, so its generalizability may be limited. CONCLUSIONS: Exome sequencing identified a genetic diagnosis in approximately 18% of Druze individuals with ESKD. These results support conducting genetic analyses in minority populations with high rates of CKD and for whom phenotypic disease specificity may be low. PLAIN-LANGUAGE SUMMARY: Chronic kidney disease (CKD) affects many people worldwide and has multiple genetic causes. However, there is limited information on the prevalence of genetic etiologies, especially among minority populations. Our national-multicenter study focused on Israeli Druze patients. Using exome-sequencing, we identified previously undetected genetic causes in nearly 20% of patients, including a new and population-specific WDR19 homozygous pathogenic variant. This mutation has not been previously described; it is extremely rare globally but is common among the Druze, which highlights the importance of studying minority populations with high rates of CKD. Our findings provide insights into the genetic basis of end-stage kidney disease in the Israeli Druze, expand the WDR19 phenotypic spectrum, and emphasize the potential value of genetic testing in such populations.

Diagnostic Utility of Exome Sequencing Among Israeli Children With Kidney Failure.

Introduction: Genetic etiologies are estimated to account for a large portion of chronic kidney diseases (CKD) in children. However, data are lacking regarding the true prevalence of monogenic etiologies stemming from an unselected population screen of children with advanced CKD. Methods: We conducted a national multicenter prospective study of all Israeli pediatric dialysis units to provide comprehensive "real-world" evidence for the genetic basis of childhood kidney failure in Israel. We performed exome sequencing and assessed the genetic diagnostic yield. Results: Between 2019 and 2022, we recruited approximately 88% (n = 79) of the children on dialysis from all 6 Israeli pediatric dialysis units. We identified genetic etiologies in 36 of 79 (45%) participants. The most common subgroup of diagnostic variants was in congenital anomalies of the kidney and urinary tract causing genes (e.g., EYA1, HNF1B, PAX2, COL4A1, and NFIA) which together explain 28% of all monogenic etiologies. This was followed by mutations in genes causing renal cystic ciliopathies (e.g., NPHP1, NPHP4, PKHD1, and BBS9), steroid-resistant nephrotic syndrome (e.g., LAGE3, NPHS1, NPHS2, LMX1B, and SMARCAL1) and tubulopathies (e.g., CTNS and AQP2). The genetic diagnostic yield was higher among Arabs compared to Jewish individuals (55% vs. 29%) and in children from consanguineous compared to nonconsanguineous families (63% vs. 29%). In 5 participants (14%) with genetic diagnoses, the molecular diagnosis did not correspond with the pre-exome diagnosis. Genetic diagnosis has a potential influence on clinical management in 27 of 36 participants (75%). Conclusion: Exome sequencing in an unbiased Israeli nationwide dialysis-treated kidney failure pediatric cohort resulted in a genetic diagnostic yield of 45% and can often affect clinical decision making.

Genetic Variants in ARHGEF6 Cause Congenital Anomalies of the Kidneys and Urinary Tract in Humans, Mice, and Frogs.

BACKGROUND: About 40 disease genes have been described to date for isolated CAKUT, the most common cause of childhood CKD. However, these genes account for only 20% of cases. ARHGEF6, a guanine nucleotide exchange factor that is implicated in biologic processes such as cell migration and focal adhesion, acts downstream of integrin-linked kinase (ILK) and parvin proteins. A genetic variant of ILK that causes murine renal agenesis abrogates the interaction of ILK with a murine focal adhesion protein encoded by Parva , leading to CAKUT in mice with this variant. METHODS: To identify novel genes that, when mutated, result in CAKUT, we performed exome sequencing in an international cohort of 1265 families with CAKUT. We also assessed the effects in vitro of wild-type and mutant ARHGEF6 proteins, and the effects of Arhgef6 deficiency in mouse and frog models. RESULTS: We detected six different hemizygous variants in the gene ARHGEF6 (which is located on the X chromosome in humans) in eight individuals from six families with CAKUT. In kidney cells, overexpression of wild-type ARHGEF6 -but not proband-derived mutant ARHGEF6 -increased active levels of CDC42/RAC1, induced lamellipodia formation, and stimulated PARVA-dependent cell spreading. ARHGEF6-mutant proteins showed loss of interaction with PARVA. Three-dimensional Madin-Darby canine kidney cell cultures expressing ARHGEF6-mutant proteins exhibited reduced lumen formation and polarity defects. Arhgef6 deficiency in mouse and frog models recapitulated features of human CAKUT. CONCLUSIONS: Deleterious variants in ARHGEF6 may cause dysregulation of integrin-parvin-RAC1/CDC42 signaling, thereby leading to X-linked CAKUT.

Poststreptococcal Myalgia and Protracted Febrile Myalgia Syndrome: Similar Yet Different.

We compare cases of familial Mediterranean fever-related protracted febrile myalgia and poststreptococcal myalgia, both rare disorders presenting with fever, myalgia, and inflammatory biomarkers. Although clinical symptoms may be undistinguishable, steroids are usually required in protracted febrile myalgia syndrome and poststreptococcal myalgia most often respond to nonsteroidal anti-inflammatory drugs. Awareness of poststreptococcal myalgia and preceding history may prevent unnecessary tests or overtreatment.

Mammalian target of rapamycin inhibitors for the treatment of astrocytic hamartoma in tuberous sclerosis complex (TSC).

PURPOSE: Tuberous sclerosis complex (TSC) is an inherited neurocutaneous disorder. Fifty percent of patients with TSC will develop retinal astrocytic hamartoma (RAH). The mammalian target of rapamycin (mTOR) inhibitors interferes with the pathological mechanisms of TSC. Treatment of RAH with mTOR inhibitors has been described in only a few isolated case reports. The purpose of this study was to assess the effect of mTOR inhibitors on RAH in a small cohort of patients. METHODS: The medical records of all consecutive patients with ocular manifestations of TSC that were treated with mTOR inhibitors at the Sheba Medical Center from January 2014 to December 2018 were retrospectively reviewed. Data collection included demographics, medical history, ocular presentation, ocular treatment, and treatment outcome. Tumor size was assessed by a masked observer, before and after treatment. Lesion measurements were made with Heidelberg SD-OCT (HRA + OCT SPECTRALIS), and fundus photos were taken with RetCam3® (Natus, USA) and analyzed by "ImageJ" software. RESULTS: Eleven patients with tuberous sclerosis and astrocytic hamartoma were treated with mTOR inhibitors in the study period. Of them, 6 children (11 eyes, 20 tumors) had proper imaging of tumor size before and after treatment. The analysis included these 11 eyes. All six patients had non-ocular manifestations of TSC, including dermatologic (n = 5), neurologic (n = 5), and renal (n = 3) involvement. Ocular involvement included in five eyes (45%) tumors near the optic disc and in four eyes (37%) foveal tumors. The mean follow-up duration was 2.15 ± 1.4 years (range 10 months to 4.5 years). The average tumor base reduction in the treated group was 17.8% ± 15.9. The average maximal thickness at baseline was 414 ± 174 µm (range 152-686 µm). There was a 14% ± 7.1 reduction after treatment. None of the tumors showed evidence of growth at the final follow-up. CONCLUSION: The findings of this study suggest that mTOR inhibitors can reduce tumor size and that they can be considered as an optional treatment in certain conditions. This preliminary report is the first to quantitatively assess pre- and posttreatment tumor size, in young patients.

A multidisciplinary nephrogenetic referral clinic for children and adults-diagnostic achievements and insights.

BACKGROUND: Genetic kidney diseases contribute a significant portion of kidney diseases in children and young adults. Nephrogenetics is a rapidly evolving subspecialty; however, in the clinical setting, increased use of genetic testing poses implementation challenges. Consequently, we established a national nephrogenetics clinic to apply a multidisciplinary model. METHODS: Patients were referred from different pediatric or adult nephrology units across the country if their primary nephrologist suspected an undiagnosed genetic kidney disease. We determined the diagnostic rate and observed the effect of diagnosis on medical care. We also discuss the requirements of a nephrogenetics clinic in terms of logistics, recommended indications for referral, and building a multidisciplinary team. RESULTS: Over 24 months, genetic evaluation was completed for a total of 74 unrelated probands, with an age range of 10 days to 72 years. The most common phenotypes included congenital anomalies of the kidneys and urinary tract, nephrotic syndrome or unexplained proteinuria, nephrocalcinosis/nephrolithiasis, tubulopathies, and unexplained kidney failure. Over 80% of patients were referred due to clinical suspicion of an undetermined underlying genetic diagnosis. A molecular diagnosis was reached in 42/74 probands, yielding a diagnostic rate of 57%. Of these, over 71% of diagnoses were made via next generation sequencing (gene panel or exome sequencing). CONCLUSIONS: We identified a substantial fraction of genetic kidney etiologies among previously undiagnosed individuals which influenced subsequent clinical management. Our results support that nephrogenetics, a rapidly evolving field, may benefit from well-defined multidisciplinary co-management administered by a designated team of nephrologist, geneticist, and bioinformatician. A higher resolution version of the Graphical abstract is available as Supplementary information.

Prediction of tuberous sclerosis-associated neurocognitive disorders and seizures via machine learning of structural magnetic resonance imaging.

PURPOSE: Tuberous sclerosis complex (TSC) is a genetic disorder characterized by multiorgan hamartomas, including cerebral lesions, with seizures as a common presentation. Most TSC patients will also experience neurocognitive comorbidities. Our objective was to use machine learning techniques incorporating clinical and imaging data to predict the occurrence of major neurocognitive disorders and seizures in TSC patients. METHODS: A cohort of TSC patients were enrolled in this retrospective study. Clinical data included genetic, demographic, and seizure characteristics. Imaging parameters included the number, characteristics, and location of cortical tubers and the presence of subependymal nodules, SEGAs, and cerebellar tubers. A random forest machine learning scheme was used to predict seizures and neurodevelopmental delay or intellectual developmental disability. Prediction ability was assessed by the area-under-the-curve of receiver-operating-characteristics (AUC-ROC) of ten-fold cross-validation training set and an independent validation set. RESULTS: The study population included 77 patients, 55% male (17.1 ± 11.7 years old). The model achieved AUC-ROC of 0.72 ± 0.1 and 0.68 in the training and internal validation datasets, respectively, for predicting neurocognitive comorbidity. Performance was limited in predicting seizures (AUC-ROC of 0.54 ± 0.19 and 0.71 in the training and internal validation datasets, respectively). The integration of seizure characteristics into the model improved the prediction of neurocognitive comorbidity with AUC-ROC of 0.84 ± 0.07 and 0.75 in the training and internal validation datasets, respectively. CONCLUSIONS: This proof of concept study shows that it is possible to achieve a reasonable prediction of major neurocognitive morbidity in TSC patients using structural brain imaging and machine learning techniques. These tools can help clinicians identify subgroups of TSC patients with an increased risk of developing neurocognitive comorbidities.

Whole-exome sequencing reveals a monogenic cause in 56% of individuals with laterality disorders and associated congenital heart defects.

BACKGROUND: The molecular basis of heterotaxy and congenital heart malformations associated with disruption of left-right asymmetry is broad and heterogenous, with over 25 genes implicated in its pathogenesis thus far. OBJECTIVE: We sought to elucidate the molecular basis of laterality disorders and associated congenital heart defects in a cohort of 30 unrelated probands of Arab-Muslim descent, using next-generation sequencing techniques. METHODS: Detailed clinical phenotyping followed by whole-exome sequencing (WES) was pursued for each of the probands and their parents (when available). Sanger sequencing was used for segregation analysis of disease-causing mutations in the families. RESULTS: Using WES, we reached a molecular diagnosis for 17 of the 30 probands (56.7%). Genes known to be associated with heterotaxy and/or primary ciliary dyskinesia, in which homozygous pathogenic or likely pathogenic variants were detected, included CFAP53 (CCDC11), CFAP298 (C21orf59), CFAP300, LRRC6, GDF1, DNAAF1, DNAH5, CCDC39, CCDC40, PKD1L1 and TTC25. Additionally, we detected a homozygous disease causing mutation in DAND5, as a novel recessive monogenic cause for heterotaxy in humans. Three additional probands were found to harbour variants of uncertain significance. These included variants in DNAH6, HYDIN, CELSR1 and CFAP46. CONCLUSIONS: Our findings contribute to the current knowledge regarding monogenic causes of heterotaxy and its associated congenital heart defects and underscore the role of next-generation sequencing techniques in the diagnostic workup of such patients, and especially among consanguineous families.

Clinical impact of exome sequencing in the setting of a general pediatric ward for hospitalized children with suspected genetic disorders.

Background: Genetic conditions contribute a significant portion of disease etiologies in children admitted to general pediatric wards worldwide. While exome sequencing (ES) has improved clinical diagnosis and management over a variety of pediatric subspecialties, it is not yet routinely used by general pediatric hospitalists. We aim to investigate the impact of exome sequencing in sequencing-naive children suspected of having monogenic disorders while receiving inpatient care. Methods: We prospectively employed exome sequencing in children admitted to the general pediatric inpatient service at a large tertiary medical center in Israel. Genetic analysis was triggered by general and/or subspecialist pediatricians who were part of the primary inpatient team. We determined the diagnostic yield among children who were referred for exome sequencing and observed the effects of genetic diagnosis on medical care. Results: A total of fifty probands were evaluated and exome sequenced during the study period. The most common phenotypes included were neurodevelopmental (56%), gastrointestinal (34%), and congenital cardiac anomalies (24%). A molecular diagnosis was reached in 38% of patients. Among seven patients (37%), the molecular genetic diagnosis influenced subsequent clinical management already during admission or shortly following discharge. Conclusion: We identified a significant fraction of genetic etiologies among undiagnosed children admitted to the general pediatric ward. Our results support that early application of exome sequencing may be maximized by pediatric hospitalists' high index of suspicion for an underlying genetic etiology, prompting an in-house genetic evaluation. This framework should include a multidisciplinary co-management approach of the primary care team working alongside with subspecialties, geneticists and bioinformaticians.

An Israeli tuberous sclerosis cohort: the efficacy of different anti-epileptic strategies.

AIM: We aimed to describe the experience of a large single-center cohort for the clinical, radiological, and genetic characteristics, as well as to determine the efficacy of different anti-epileptic strategies in children and adults with tuberous sclerosis complex (TSC). METHODS: We carried out a historical cohort study on 91 TSC patients treated in a single center between 2008 and 2018. RESULTS: Our cohort comprised 46 males and 45 females, with a median age of 15.6 years at the last follow-up. Mean follow-up time was 2.5 ± 0.75-5.5 years (range 0-9.5 years). Of those tested, a disease-causing mutation was identified in 90% of patients, 53% in TSC2, and 37% in TSC1. Epilepsy prevalence was similar among TSC1 and TSC2 mutated patients. The most common radiological finding were cortical tubers in 95% of patients, while subependymal giant cell astrocytoma (SEGA) were detected in 36% of patients. Notably, infantile spasms (IS) were diagnosed in 29%, with SEGA representing the only finding significantly different in prevalence between those with and without IS (62% vs. 28%, respectively, p = 0.009). Lastly, we did not find any difference in efficacy between three anti-epileptic treatments: Vagus nerve stimulation (VNS), CBD-based products, and the ketogenic diet, all showing approximately 30%-40% response rates. SIGNIFICANCE: Altogether, we provide a comprehensive description of our experience in treating TSC, which could serve to expand current knowledge of the disease and its treatments.