HNF1B-associated renal and extra-renal disease—an expanding clinical spectrum

Elucidating the Molecular Landscape of Cystic Kidney Disease: Old Friends, New Friends and Some Surprises

Cystic kidney diseases (CyKD) are a diverse group of disorders affecting more than 1 in 1000 individuals. Over 120 genes are implicated, primarily encoding components of the primary cilium, transcription factors, and morphogens. Prognosis varies greatly by molecular diagnosis. Causal variants are not identified in 10%-60% of individuals due to our limited understanding of CyKD. To elucidate the molecular landscape of CyKD, we queried the CAG Biobank using the ICD10 codes N28.1, Q61.1, Q61.11, Q61.19, Q61.2, Q61.3, and Q61.8 to identify individuals with CyKD. One hundred eight individuals met clinical criteria for CyKD and underwent proband-only exome sequencing. Causal variants were identified in 86/108 (80%) individuals. The most common molecular diagnoses were PKD1-related autosomal dominant polycystic kidney disease (32/108; 30%) and autosomal recessive polycystic kidney disease (21/108; 19%). Other common molecular diagnoses were ciliopathy syndromes (7/108; 6.5%) and Tuberous Sclerosis (6/108; 5.6%). Seven individuals had variants in genes not previously associated with CyKD (7/108; 6.5%). Candidate genes were identified in five individuals (5/108; 4.5%). Discordance between molecular and clinical diagnosis was present in two individuals. We demonstrate a high molecular diagnosis rate in individuals with CyKD that can result in diagnostic reclassification, supporting a role for genetic testing in CyKD.

Genitourinary defects, anxiety and aggressive-like behavior and glucose metabolism disorders in Zmym2 mutant mice with inserted piggyBac transposon

Mutations in ZMYM2 lead to syndromic congenital anomalies of the kidney and urinary tract (CAKUT) in humans. Tbx18 is co-expressed with Zmym2 in mesenchymal compartment of developing mouse ureter, indicating a potential in vivo relevance of the TBX18-ZMYM2 protein interaction in ureter development. The presence of multiple phenotypes beyond the urinary system in CAKUT patients carrying ZMYM2 mutations suggests that ZMYM2 has extensive roles in various developmental processes. This study aims to comprehensively examine the multi-phenotypic consequence of ZMYM2 mutations, with a particular focus on the roles of ZMYM2 in embryonic development, late metanephros formation, and the reproductive, nervous and endocrine systems, in addition to its role in urinary system. Using a new Zmym2 mutant mouse model with an inserted piggyBac transposon (PB), we found that homozygous Zmym2 mutations resulted in severe growth retardation of embryos by embryonic day 9.5 (E9.5D) and lethality from E10.5D. Heterozygous mutations caused morphogenetic issues in the genitourinary system, including duplex kidneys, vesicoureteral reflux (VUR), and cryptorchidism. And these heterozygous mutants exhibited anxiety and aggressive-like behaviors, and glucose metabolism disorders. Additionally, Zmym2 mutations induced duplicated ureteric bud (UB) eruption and abnormal nephrogenic zone extension, contributing to duplex kidney formation. Reduced apoptosis in the nephric duct might have contributed to abnormal ureter-bladder connections, which could explain the observed cases of VUR. Notably, Tbx18 is co-expressed with Zmym2 in mouse kidney, reduced Tbx18 expression in Zmym2 mutants further supports the hypothesis that Zmym2 interacts with Tbx18 during kidney development. Zmym2 PB mouse is the first model to demonstrate roles of Zmym2 in neuroethology and endocrinology, extending its significant beyond genitourinary defects and embryonic development. Further investigation of these phenotypes in CAKUT patients carrying ZMYM2 mutations will enhance our understanding of their phenotypes and improve strategies for early diagnosis, monitoring, and treatment.

Transcriptome analysis of multiple tissues and identification of tissue-specific genes in Lueyang black-bone chicken

Systematically constructing a gene expression atlas of poultry tissues is critically important for advancing poultry research and production. In this study, the gene expression profiles of 9 major tissues of Lueyang black-bone chicken were successfully constructed by transcriptome sequencing technology. Through in-depth analysis of transcriptome data, a total of 10 housekeeping genes (HKGs) and 87 marker genes (MGs) were identified. Furthermore, by applying weighted gene co-expression network analysis (WGCNA), we delineated nine tissue-specific modules and 90 hub genes, offering novel insights into the regulatory networks underlying tissue-specific gene expression. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that HKGs were predominantly involved in maintaining fundamental cellular functions, with significant enrichment in pathways related to oxidative phosphorylation, cell cycle regulation, and DNA replication. MGs were closely associated with tissue-specific physiological functions, providing valuable insights into the molecular mechanisms governing tissue functionality. Notably, through multidimensional validation, EEF1A1 and FTH1 were confirmed to exhibit cross-tissue expression stability, establishing them as ideal reference genes for multi-tissue qPCR experiments in chickens. Additionally, we successfully identified tissue marker genes, including TNNT2, PIT54, SFTPC, and PGM1, which are specific to the heart, liver, lung, and breast muscle, respectively. The results of this study have important scientific value in expanding reference gene selection and elucidating tissue-specific molecular mechanisms, and provide solid theoretical support and technical guidance for poultry breeding improvement and production practice optimization.

Case-based learning: a case of maturity-onset diabetes of the young 5 (MODY5) due to 17q12 microdeletion with a diminished plasma glucagon level

Maturity-onset diabetes of the young type 5 (MODY5), causally associated with loss-of-function of the HNF1B gene, is a rare form of monogenic diabetes that has been underdiagnosed in part because microdeletions of chromosome 17q12 encompassing the HNF1B gene cannot be detected by sequencing-based approaches, which accounts for about 50% of MODY5 cases. We herein describe a 37-year-old Japanese woman who manifested diabetic ketosis at the onset. The coexistence of features associated with MODY5, including abnormal renal function, impaired insulin secretion, pancreatic hypoplasia and hypomagnesemia, prompted us to decode her genomic information using whole-exome sequencing, where we were not able to identify any pathogenic HNF1B gene mutations. We further examined her genomic integrity using multiplex ligation probe amplification (MLPA) analysis, leading to identification of the 17q12 microdeletion which was further supported by array comparative genomic hybridization (array-CGH). Her insulin secretory capacity was insufficient, whereas her total daily dose of insulin was 11 U/day (0.25 U/Kg/day), indicating that she was relatively sensitive to insulin. As a possible explanation, we found that her plasma glucagon level was below the detection limit. Since inactivation of acetyl-CoA carboxylase 1 (ACACA), encoded in close proximity to the HNF1B gene, was reported to blunt glucagon secretion, the concurrent deletion of the ACACA gene may be in part responsible for this manifestation. In conclusion, the genetic analyses of MODY5 cases require the judicious use of appropriate genetic technologies. In addition, alpha-cell dysfunction may at least in part account for the variable clinical manifestations of MODY5.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13340-025-00804-2.

Navigating Genetic Testing in Nephrology: Options and Decision-Making Strategies

Technological advances such as next-generation sequencing (NGS) have enabled high-throughput assessment of the human genome, supporting the usage of genetic testing as a first-line tool across clinical medicine. Although individually rare, genetic causes account for end-stage renal disease in 10% to 15% of adults and 70% of children, and in many of these individuals, genetic testing can identify a specific etiology and meaningfully impact management. However, with numerous options for genetic testing available, nephrologists may feel uncomfortable integrating genetics into their clinical practice. Here, we aim to demystify the process of genetic test selection and highlight the opportunities for interdisciplinary collaboration between nephrologists and genetics professionals, thereby supporting precision medicine for patients with kidney disease. We first detail the various clinical genetic testing modalities, highlighting their technical advantages and limitations, and then discuss indications for their usage. Next, we provide a generalized workflow for genetic test selection among individuals with kidney disease and illustrate how this workflow can be applied to genetic test selection across diverse clinical contexts. We then discuss key areas related to the usage of genetic testing in clinical nephrology that merit further research and approaches to investigate them.

Monogenic Diabetes: A Comprehensive Overview and Therapeutic Management of Subtypes of Mody

BACKGROUND

Monogenic diabetes often occurs as a result of single-gene mutations. The illness is minimally affected by environmental and behavioral factors, and it constitutes around one to five percent of all cases of diabetes.

METHODS

Newborn diabetes mellitus (NDM) and maturity-onset diabetes of the young (MODY) are the predominant causes of monogenic diabetes, accounting for a larger proportion of cases, while syndromic diabetes represents a smaller percentage. MODY, a group of inherited non-autoimmune diabetes mellitus disorders, is quite common. However, it remains frequently misdiagnosed despite increasing public awareness. The condition is characterized by insulin resistance, the development of diabetes at a young age (before 25 years), mild high blood sugar levels, inheritance in an autosomal dominant pattern, and the preservation of natural insulin production.

RESULTS

Currently, there are 14 distinct subtypes of MODY that have been identified. Each subtype possesses distinct characteristics in terms of their frequency, clinical symptoms, severity of diabetes, related complications, and response to medicinal interventions. Due to the clinical similarities, lack of awareness, and high expense of genetic testing, distinguishing between type I (T1D) and type II diabetes mellitus (T2D) can be challenging, resulting in misdiagnosis of this type of diabetes. As a consequence, a significant number of individuals are being deprived of adequate medical attention. Accurate diagnosis enables the utilization of novel therapeutic strategies and enhances the management of therapy in comparison to type II and type I diabetes.

CONCLUSION

This article offers a concise overview of the clinical subtypes and characteristics of monogenic diabetes. Furthermore, this article discusses the various subtypes of MODY, as well as the process of diagnosing, managing, and treating the condition. It also addresses the difficulties encountered in detecting and treating MODY.

The role of chromatin-related epigenetic modulations in CAKUT

Congenital anomalies of the kidney and urinary tract (CAKUT) represent a major health burden in humans. Phenotypes range from renal hypoplasia or renal agenesis, cystic renal dysplasia, duplicated or horseshoe kidneys to obstruction of the ureteropelvic junction, megaureters, duplicated ureters, urethral valves or bladder malformations. Over the past decade, next-generation sequencing has identified numerous causative genes; however, the genetic basis of most cases remains unexplained. It is assumed that environmental factors have a significant impact on the phenotype, but, overall, the pathogenesis has remained poorly understood. Interestingly however, CAKUT is a common phenotypic feature in two human syndromes, Kabuki and Koolen-de Vries syndrome, caused by dysfunction of genes encoding for KMT2D and KANSL1, both members of protein complexes playing an important role in histone modifications. In this chapter, we discuss current knowledge regarding epigenetic modulation in renal development and a putatively under-recognized role of epigenetics in CAKUT.

Characterization of T-bet expressing B cells in lupus patients indicates a putative prognostic and therapeutic value of these cells for the disease

OBJECTIVE

To investigate whether T-bet+ B cells, as well as age-associated B cells/ABCs (CD19 + CD21-CD11c + T-bet+) and double-negative B cells/DN (CD19 + IgD-CD27- CXCR5-T-bet+), serve as prognostic and/or therapeutic tools for systemic lupus erythematosus (SLE) in humans.

METHODS

Flow cytometry was used for enumerating T-bet+ B cells and ABCs/DN subsets, found in the peripheral blood of 10 healthy donors and 22 active SLE patients. Whole blood assay cultures, combined with in vitro pharmacological treatments, were performed to evaluate the effects of hydroxychloroquine, anifrolumab, and fasudil (a ROCK kinase inhibitor) on T-bet+ B cells' percentage. Moreover, previously published single-cell RNA sequencing (scRNA-seq) data were used in a meta-analysis to allow characterization of genes and pathways associated with the biology of T-bet in B cells.

RESULTS

T-bet+ B cells displayed an expansion in SLE patients [1.47 (1.9-0.7) vs 10.85 (37.4-3.6)]. Similarly, both ABCs and DN were found to be expanded. Interestingly, percentages of T-bet+ B cells positively correlated with patients' SLEDAI scores (rs = 0.55, P = 0.007). Cell culture experiments conducted revealed that all three agents tested can deplete T-bet + B cells (without affecting the cell viability of lymphocytes, T cells, and B cells). According to bioinformatics analyses, T-bet is highly expressed in two B-cell clusters with pathogenic characteristics for SLE (designated as atypical memory B cells and activated naïve B cells). These clusters can be targeted for therapeutic interventions.

CONCLUSIONS

T-bet+ B cells can serve as a putative prognostic biomarker of lupus severity. Circumstantial data suggest that these cells may promote disease pathogenesis and may represent a novel therapeutic target.

A Novel Heterozygous and Pathogenic Variant of the HNF1B Gene Associated with Autosomal Dominant Tubulointerstitial Kidney Disease with a Broad Spectrum of Extrarenal Phenotypes: A Case Report

We encountered a family with hereditary renal failure, renal medullary cysts, pancreatic hypoplasia, hypomagnesemia, liver enzyme abnormalities, and diabetes mellitus (DM). We identified a novel heterozygous variant of HNF1B (NM_000458.4:c.791dup, p.L264Ffs*30) using whole-exome sequencing of genomic DNA samples from this family. This variant is located in the DNA-binding domain of the HNF1B protein and produces a truncated protein with a de novo sequence, suggesting that this variant changes HNF1B binding to genomic DNA or causes nonsense-mediated mRNA decay. Based on the phenotypes and identified gene variants, this family suffers from autosomal dominant tubulointerstitial kidney disease caused by this HNF1B variant.

Urinary Dickkopf-3 Reflects Disease Severity and Predicts Short-Term Kidney Function Decline in Renal Ciliopathies

Introduction

Phenotypic heterogeneity and unpredictability of individual disease progression present enormous challenges in ultrarare renal ciliopathies. The tubular-derived glycoprotein, Dickkopf-related protein 3 (DKK3) is a promising biomarker for kidney fibrosis and prediction of kidney function decline. Here, we measured urinary DKK3 (uDKK3) levels in 195 pediatric patients with renal ciliopathy to assess its potential as a discriminative and prediction marker.

Methods

uDKK3 concentration was measured in 357 spot urine samples from 247 individuals, including 52 healthy age-matched controls. Disease entities comprised nephronophthisis (NPH) (n = 37), autosomal recessive polycystic kidney disease (ARPKD) (n = 61), Bardet Biedl syndrome (BBS) (n = 57), and hepatocyte nuclear factor 1 beta (HNF1B)-nephropathy (n = 40). The results were correlated with chronic kidney disease (CKD) stage and annual estimated glomerular filtration rate (eGFR) decline.

Results

Median uDKK3-to-creatinine ratios (uDKK3/crea) in all disease entities were significantly higher compared with healthy controls (11pg/mg uDKK3/crea, P < 0.001): NPH, 1.219 pg/mg; HNF1B, 731 pg/mg; BBS, 541 pg/mg; and ARPKD, 437 pg/mg. A significant correlation of CKD stage with uDKK3 levels was observed for all disease entities (P < 0.0001) with no other clinical parameter having a relevant impact. In our cohort, uDKK3 values >4.700 pg/mg were associated with a significantly greater annual eGFR loss independently of diagnosis and eGFR (P = 0.0029). Although we observed a trend toward lower uDKK3 levels in glomerulopathies compared to renal ciliopathies, there was no discriminative difference between individual ciliopathy entities (P = 0.2637).

Conclusion

In renal ciliopathies, uDKK3 is a marker to assess disease severity and estimate short-term kidney function decline.

A novel mutation in HNF1B promotes ferroptosis-mediated renal mesangial cells fibrosis

Maturity onset diabetes of the young type 5(MODY5) is typically attributed to mutations in the HNF1B gene, which encodes transcription factors that play a significant role in kidney development and function maintenance. In this study, we identified a novel HNF1B gene mutation (c.445C > A) in a young male MODY5 patient exhibiting elevated serum creatinine levels and albuminuria. Through transfection of wild type and mutant HNF1B plasmids into mouse mesangial cells (MMCs), we investigated the impact on molecular indicators related to proliferation, fibrosis and oxidative stress. The results revealed that the HNF1B novel mutation promoted the expression of fibronectin, type 1 collagen, and CyclinD1, as well as increasing cellular oxidative stress and susceptibility to ferroptosis in MMCs. Our findings established a novel association between HNF1B mutant diseases and mesangial cell proliferation and fibrosis, suggesting that mutations of HNF1B may contribute to the progression of renal function in MODY5 patients. Additionally, our results implicate potential therapeutic targets for restraining fibrosis.

Approach to simple kidney cysts in children

The finding of a simple kidney cyst in a child can pose a diagnostic and management challenge for pediatric nephrologists, urologists, and primary care providers. The reported prevalence varies from 0.22 to 1% in large ultrasonography-based series of more than 10,000 children each. The true prevalence, however, may be higher or lower, as factors such as variations in referral patterns, indications for ultrasonography, or technical considerations could impact prevalence rates. For many patients, simple kidney cysts may be found incidentally when imaging is performed for another indication. Although simple cysts can occur in children, they may also represent the first sign of autosomal dominant polycystic kidney disease (ADPKD) or other less common cystic kidney diseases. Definitive guidelines regarding the evaluation and monitoring of children with simple kidney cysts have not been established. The desire on the part of the practitioner and/or parents to establish a definitive diagnosis should be balanced with the cost and inconvenience of repeated imaging and visits with specialists. The goals of this review are to (1) outline the definition, epidemiology, clinical presentation, and natural history of simple kidney cysts in childhood; (2) describe clinical features that could suggest a diagnosis other than a simple kidney cyst; and (3) present a suggested framework for evaluating and monitoring of children with one or more simple kidney cysts.

A framework for target discovery in rare cancers

While large-scale functional genetic screens have uncovered numerous cancer dependencies, rare cancers are poorly represented in such efforts and the landscape of dependencies in many rare cancers remains obscure. We performed genome-scale CRISPR knockout screens in an exemplar rare cancer, TFE3-translocation renal cell carcinoma (tRCC), revealing previously unknown tRCC-selective dependencies in pathways related to mitochondrial biogenesis, oxidative metabolism, and kidney lineage specification. To generalize to other rare cancers in which experimental models may not be readily available, we employed machine learning to infer gene dependencies in a tumor or cell line based on its transcriptional profile. By applying dependency prediction to alveolar soft part sarcoma (ASPS), a distinct rare cancer also driven by TFE3 translocations, we discovered and validated that MCL1 represents a dependency in ASPS but not tRCC. Finally, we applied our model to predict gene dependencies in tumors from the TCGA (11,373 tumors; 28 lineages) and multiple additional rare cancers (958 tumors across 16 types, including 13 distinct subtypes of kidney cancer), nominating potentially actionable vulnerabilities in several poorly-characterized cancer types. Our results couple unbiased functional genetic screening with a predictive model to establish a landscape of candidate vulnerabilities across cancers, including several rare cancers currently lacking in potential targets.

HNF1β bookmarking involves Topoisomerase 1 activation and DNA topology relaxation in mitotic chromatin

HNF1β (HNF1B) is a transcription factor frequently mutated in patients with developmental renal disease. It binds to mitotic chromatin and reactivates gene expression after mitosis, a phenomenon referred to as bookmarking. Using a crosslinking method that circumvents the artifacts of formaldehyde, we demonstrate that HNF1β remains associated with chromatin in a sequence-specific way in both interphase and mitosis. We identify an HNF1β-interacting protein, BTBD2, that enables the interaction and activation of Topoisomerase 1 (TOP1) exclusively during mitosis. Our study identifies a shared microhomology domain between HNF1β and TOP1, where a mutation, found in "maturity onset diabetes of the young" patients, disrupts their interaction. Importantly, HNF1β recruits TOP1 and induces DNA relaxation around HNF1β mitotic chromatin sites, elucidating its crucial role in chromatin remodeling and gene reactivation after mitotic exit. These findings shed light on how HNF1β reactivates target gene expression after mitosis, providing insights into its crucial role in maintenance of cellular identity.

HNF1B Transcription Factor: Key Regulator in Renal Physiology and Pathogenesis

The HNF1B gene, located on chromosome 17q12, encodes a transcription factor essential for the development of several organs. It regulates the expression of multiple genes in renal, pancreatic, hepatic, neurological, and genitourinary tissues during prenatal and postnatal development, influencing processes such as nephrogenesis, cellular polarity, tight junction formation, cilia development, ion transport in the renal tubule, and renal metabolism. Mutations that alter the function of Hnf1b deregulate those processes, leading to various pathologies characterized by both renal and extrarenal manifestations. The main renal diseases that develop are polycystic kidney disease, hypoplastic or dysplastic kidneys, structural abnormalities, Congenital Anomalies of the Kidney and Urinary Tract (CAKUT), and electrolyte imbalances such as hyperuricemia and hypomagnesemia. Extrarenal manifestations include Maturity-Onset Diabetes of the Young (MODY), hypertransaminasemia, genital and urinary tract malformations, Autism Spectrum Disorder (ASD), and other neurodevelopmental disorders. Patients with HNF1B alterations typically carry either punctual mutations or a monoallelic microdeletion in the 17q12 region. Future research on the molecular mechanisms and genotype-phenotype correlations in HNF1B-related conditions will enhance our understanding, leading to improved clinical management, genetic counseling, monitoring, and patient care.

Monogenic Defects of Beta Cell Function: From Clinical Suspicion to Genetic Diagnosis and Management of Rare Types of Diabetes

Monogenic defects of beta cell function refer to a group of rare disorders that are characterized by early-onset diabetes mellitus due to a single gene mutation affecting insulin secretion. It accounts for up to 5% of all pediatric diabetes cases and includes transient or permanent neonatal diabetes, maturity-onset diabetes of the young (MODY), and various syndromes associated with diabetes. Causative mutations have been identified in genes regulating the development or function of the pancreatic beta cells responsible for normal insulin production and/or release. To date, more than 40 monogenic diabetes subtypes have been described, with those caused by mutations in HNF1A and GCK genes being the most prevalent. Despite being caused by a single gene mutation, each type of monogenic diabetes, especially MODY, can appear with various clinical phenotypes, even among members of the same family. This clinical heterogeneity, its rarity, and the fact that it shares some features with more common types of diabetes, can make the clinical diagnosis of monogenic diabetes rather challenging. Indeed, several cases of MODY or syndromic diabetes are accurately diagnosed in adulthood, after having been mislabeled as type 1 or type 2 diabetes. The recent widespread use of more reliable sequencing techniques has improved monogenic diabetes diagnosis, which is important to guide appropriate treatment and genetic counselling. The current review aims to summarize the latest knowledge on the clinical presentation, genetic confirmation, and therapeutic approach of the various forms of monogenic defects of beta cell function, using three imaginary clinical scenarios and highlighting clinical and laboratory features that can guide the clinician in reaching the correct diagnosis.

A Korean Family Presenting with Renal Cysts and Maturity-Onset Diabetes of the Young Caused by a Novel In-Frame Deletion of HNF1B

Maturity-onset diabetes of the young (MODY; OMIM # 606391) comprises a cluster of inherited disorders within non-autoimmune diabetes mellitus (DM), typically emerging during adolescence or young adulthood. We report a novel in-frame deletion of HNF1B in a family with renal cysts and MODY, furthering our understanding of HNF1B-related phenotypes. We conducted sequential genetic testing to investigate the glucose intolerance, renal cysts, hepatic cysts, and agenesis of the dorsal pancreas observed in the proband. A comprehensive clinical exome sequencing approach using a Celemics G-Mendeliome Clinical Exome Sequencing Panel was employed. Considering the clinical manifestations observed in the proband, gene panel sequencing identified a heterozygous HNF1B variant, c.36_38delCCT/p.(Leu13del) (reference transcript ID: NM_000458.4), as the most likely cause of MODY in the proband. The patient's clinical presentation was consistent with MODY caused by the HNF1B variant, showing signs of glucose intolerance, renal cysts, hepatic cysts, and agenesis of the dorsal pancreas. Sanger sequencing confirmed the same HNF1B variant and established the paternally inherited autosomal dominant status of the heterozygous variant in the patient, as well as in his father and sister. The presence of early-onset diabetes, renal cysts, a family history of the condition, and nephropathy appearing before or after the diagnosis of diabetes mellitus (DM) suggests a diagnosis of HNF1B-MODY5. Early diagnosis is crucial for preventing complications of DM, enabling family screening, providing pre-conceptional genetic counseling, and monitoring kidney function decline.

Practical Approach to Congenital Anomalies of the Kidneys: Focus on Anomalies With Insufficient or Abnormal Nephron Development: Renal Dysplasia, Renal Hypoplasia, and Renal Tubular Dysgenesis

Congenital anomalies of the kidney and urinary tract (CAKUT) accounts for up to 30% of antenatal congenital anomalies and is the main cause of kidney failure in children worldwide. This review focuses on practical approaches to CAKUT, particularly those with insufficient or abnormal nephron development, such as renal dysplasia, renal hypoplasia, and renal tubular dysgenesis. The review provides insights into the histological features, pathogenesis, mechanisms, etiologies, antenatal and postnatal presentation, management, and prognosis of these anomalies. Differential diagnoses are discussed as several syndromes may include CAKUT as a phenotypic component and renal dysplasia may occur in some ciliopathies, tumor predisposition syndromes, and inborn errors of metabolism. Diagnosis and genetic counseling for CAKUT are challenging, due to the extensive variability in presentation, genetic and phenotypic heterogeneity, and difficulties to assess postnatal lung and renal function on prenatal imaging. The review highlights the importance of perinatal autopsy and pathological findings in surgical specimens to establish the diagnosis and prognosis of CAKUT. The indications and the type of genetic testing are discussed. The aim is to provide essential insights into the practical approaches, diagnostic processes, and genetic considerations offering valuable guidance for pediatric and perinatal pathologists.

High prevalence of copy number variations in the Japanese participants with suspected MODY

Maturity-Onset Diabetes of the Young (MODY) is a diabetes mellitus subtype caused by a single gene. The detection rate of the responsible gene is 27% in the United Kingdom, indicating that the causative gene remains unknown in the majority of clinically diagnosed MODY cases. To improve the detection rate, we applied comprehensive genetic testing using whole exome sequencing (WES) followed by Multiplex Ligation-dependent Probe Amplification (MLPA) and functional analyses. Twenty-one unrelated Japanese participants with MODY were enrolled in the study. To detect copy number variations (CNVs), WES was performed first, followed by MLPA analysis for participants who were negative on the basis of WES. Undetermined variants were analyzed according to their functional properties. WES identified 7 pathogenic and 3 novel likely pathogenic variants in the 21 participants. Functional analyses revealed that 1 in 3 variants was pathogenic. MLPA analysis applied to the remaining 13 undetermined samples identified 4 cases with pathogenic CNVs: 3 in HNF4A and 1 in HNF1B. Pathogenic variants were identified in 12 participants (12/21, 57.1%) - relatively high rate reported to date. Notably, one-third of the participants had CNVs in HNF4A or HNF1B, indicating a limitation of WES-only screening.

Challenges in the management of patients with HNF1B MODY and multisystem manifestations: the cases of two adolescent boys

INTRODUCTION

Hepatocyte nuclear factor-1 beta (HNF1B) encodes a homeodomain-containing transcription factor, which is expressed early in embryogenesis and is involved in the development of multiple tissues and organs. HNF1B mutations cause complex multisystem disorders, with renal developmental disease and maturity onset diabetes of the young (HNF1B MODY), a rare cause of diabetes mellitus, being representative features.

METHODS

We present two adolescent boys from different socioeconomic backgrounds who were diagnosed with genetically confirmed HNF1B MODY following hospitalization for diabetic ketoacidosis in the first case and after diagnostic work-up due to impaired glucose tolerance in the second case. Multisystem manifestations, including pancreatic hypoplasia and early-onset diabetes mellitus (DM), renal cysts, hypomagnesemia, hyperuricemia, liver and biliary impairment, genital tract malformations, and primary hyperparathyroidism were also present, strongly suggesting HNF1B MODY.

RESULTS

The first patient was treated with subcutaneous insulin but was lost to follow-up due to social reasons. Conversely, early diagnosis in the second patient allowed the management of multisystem defects by a multidisciplinary team of experts. Moreover, manifestation of HNF1B MODY in the form of diabetic ketoacidosis was prevented and a structured diabetes training program has proven successful in regulating glycemic control, postponing the necessity for insulin treatment.

CONCLUSION

Early genetic work-up of patients with dysglycemia associated with a specific phenotype suggestive of HNF1B MODY is extremely important in the care of children and adolescents with diabetes since it ensures that early and optimal management is initiated, thereby preventing the onset of life-threatening diabetic ketoacidosis and other multisystem complications and/or comorbidities.

HNF1β, LHX1, and GGNBP2 deletion contributed to kidney and reproductive dysfunction in 17q12 deletion syndrome: evidence from a case report

17q12 deletion syndrome is a chromosomal abnormality, where there is a small missing piece (deletion) of genetic material on the long arm (q) of chromosome 17. Sign and symptoms can vary widely among different patients. Recently, a patient was diagnosed with 17q12 deletion syndrome in our hospital, and the clinical characteristics presented as absence of the right kidney, compensatory hypertrophy of the left kidney, multiple small cysts in the left kidney, pancreatic atrophy, hypomagnesemia, bowed uterus, multiple follicular cysts in both lobes of the thyroid gland, and maturity-onset diabetes of the young type 5 (MODY-5). A 1.5-Mb deletion with haploinsufficiency for 20 genes within the 17q12 region was found through copy number variation (CNV) analysis based on metagenomic next-generation sequencing (mNGS) technology. In addition to HNF1B absence, the LIM-class homeobox 1 transcription factor (LHX1) and GGNBP2 absence was also involved in regulation of kidney development and the reproductive system through bioinformatics analysis. The inheriting risk of 17q12 deletion syndrome is about 50%, and it is recommended to provide genetic counseling to all patients who are suspected or diagnosed with the syndrome.

The Impact of Autosomal Dominant Polycystic Kidney Disease in Children: A Nephrological, Nutritional, and Psychological Point of View

Autosomal dominant polycystic kidney disease (ADPKD) is a hereditary disorder characterized by the formation of numerous fluid-filled cysts in the kidneys, leading to progressive renal failure and various extrarenal complications, including hypertension. This review explores the genetic basis of ADPKD, including emerging evidence of epigenetic mechanisms in modulating gene expression and disease progression in ADPKD. Furthermore, it proposes to examine the pathological characteristics of this condition at the nephrological, cardiovascular, nutritional, and psychological levels, emphasizing that the follow-up of patients with ADPKD should be multidisciplinary from a young pediatric age.

The Role of Genetic Testing in Adult CKD

Mounting evidence indicates that monogenic disorders are the underlying cause in a significant proportion of patients with CKD. In recent years, the diagnostic yield of genetic testing in these patients has increased significantly as a result of revolutionary developments in genetic sequencing techniques and sequencing data analysis. Identification of disease-causing genetic variant(s) in patients with CKD may facilitate prognostication and personalized management, including nephroprotection and decisions around kidney transplantation, and is crucial for genetic counseling and reproductive family planning. A genetic diagnosis in a patient with CKD allows for screening of at-risk family members, which is also important for determining their eligibility as kidney transplant donors. Despite evidence for clinical utility, increased availability, and data supporting the cost-effectiveness of genetic testing in CKD, especially when applied early in the diagnostic process, many nephrologists do not use genetic testing to its full potential because of multiple perceived barriers. Our aim in this article was to empower nephrologists to (further) implement genetic testing as a diagnostic means in their clinical practice, on the basis of the most recent insights and exemplified by patient vignettes. We stress why genetic testing is of significant clinical benefit to many patients with CKD, provide recommendations for which patients to test and which test(s) to order, give guidance about interpretation of genetic testing results, and highlight the necessity for and essential components of pretest and post-test genetic counseling.

Renal and Extrarenal Phenotypes in Patients With HNF1B Variants and Chromosome 17q12 Microdeletions

Introduction

Hepatocyte nuclear factor 1-beta (HNF1B) gene variants or the chromosome 17q12 deletion (17q12del) represent the most common monogenic cause of developmental kidney disease. Although neurodevelopmental disorders have been associated with the 17q12del, specific genotype-phenotype associations with respect to kidney function evolution have not yet been fully defined. Here, we aimed to determine whether 17q12del or specific HNF1B variants were associated with kidney survival in a large patient population with HNF1B disease.

Methods

This was a retrospective observational study involving 521 patients with HNF1B disease from 14 countries using the European Reference Network for rare kidney diseases with detailed information on the HNF1B genotype (HNF1B variants or the 17q12del). Median follow-up time was 11 years with 6 visits per patient. The primary end point was progression to chronic kidney disease (CKD) stage 3 (estimated glomerular filtration rate [eGFR] < 60 ml/min per 1.73 m2). Secondary end points were the development of hypomagnesemia or extrarenal disorders, including hyperuricemia and hyperglycemia.

Results

Progression toward CKD stage 3 was significantly delayed in patients with the 17q12del compared to patients with HNF1B variants (hazard ratio [HR]: 0.29, 95% confidence interval [CI]: 0.19-0.44, P < 0.001). Progression toward CKD stage 3 was also significantly delayed when HNF1B variants involved the HNF1B Pit-1, Oct-1, and Unc-86 homeodomain (POUh) DNA-binding and transactivation domains rather than the POU-specific domain (POUs) DNA-binding domain (HR: 0.15 [95% CI: 0.06-0.37), P < 0.001 and HR: 0.25 (95% CI: 0.11-0.57), P = 0.001, respectively). Finally, the 17q12del was positively associated with hypomagnesemia and negatively associated with hyperuricemia, but not with hyperglycemia.

Conclusion

Patients with the 17q12del display a significantly better kidney survival than patients with other HNF1B variants; and for the latter, variants in the POUs DNA-binding domain lead to the poorest kidney survival. These are clinically relevant HNF1B kidney genotype-phenotype correlations that inform genetic counseling.

A Case of 17q12 Microdeletion Syndrome in a MODY5 Type Diabetes with HNF-1β Gene Mutation Accompanied

Maturity Onset Diabetes of the Young (MODY) is an autosomal dominant inherited disorder prevalent among adolescents. Typically, it manifests with hyperglycemia before the age of 25. MODY5 is attributed to a mutation in the Hepatocyte Nuclear Factor-1β (HNF-1β) gene. A complete absence of HNF-1β is observed in 50% of those with MODY5. The 17q12 microdeletion syndrome closely linked with MODY5. Its incidence in the general population is around 1 in 14,500 and is linked with facial deformities, diabetes, polycystic kidneys, pancreatic hypertrophy, liver anomalies, and neuropsychological impairments. The most primary clinical signs are predominantly associated with the HNF-1β gene deletion. We chronicle the case of a male of 19 years of age diagnosed with diabetes, who, alongside persistent liver damage and polycystic kidneys, was referred from a community hospital to the Xuzhou Central Hospital. His clinical presentation included diabetes, liver dysfunction, polycystic kidneys, lipid irregularities, insulin resistance, and fatty atrophy. Subsequent genetic screening unveiled a 17q12 chromosomal deletion and an absence of the Hepatocyte Nuclear Factor-1β (HNF-1β) gene. Hence, for adolescent patients lacking a familial diabetes history but exhibiting symptoms like polycystic kidneys, liver damage, lipid irregularities, and fatty atrophy, a thorough assessment for the 17q12 microdeletion syndrome becomes imperative.

Stepwise developmental mimicry generates proximal-biased kidney organoids

The kidney maintains body fluid homeostasis by reabsorbing essential compounds and excreting waste. Proximal tubule cells, crucial for renal reabsorption of a range of sugars, ions, and amino acids, are highly susceptible to damage, leading to pathologies necessitating dialysis and kidney transplants. While human pluripotent stem cell-derived kidney organoids are used for modeling renal development, disease, and injury, the formation of proximal nephron cells in these 3D structures is incomplete. Here, we describe how to drive the development of proximal tubule precursors in kidney organoids by following a blueprint of in vivo human nephrogenesis. Transient manipulation of the PI3K signaling pathway activates Notch signaling in the early nephron and drives nephrons toward a proximal precursor state. These "proximal-biased" (PB) organoid nephrons proceed to generate proximal nephron precursor cells. Single-cell transcriptional analyses across the organoid nephron differentiation, comparing control and PB types, confirm the requirement of transient Notch signaling for proximal development. Indicative of functional maturity, PB organoids demonstrate dextran and albumin uptake, akin to in vivo proximal tubules. Moreover, PB organoids are highly sensitive to nephrotoxic agents, display an injury response, and drive expression of HAVCR1 / KIM1 , an early proximal-specific marker of kidney injury. Injured PB organoids show evidence of collapsed tubules, DNA damage, and upregulate the injury-response marker SOX9 . The PB organoid model therefore has functional relevance and potential for modeling mechanisms underpinning nephron injury. These advances improve the use of iPSC-derived kidney organoids as tools to understand developmental nephrology, model disease, test novel therapeutics, and for understanding human renal physiology.

Navigating the multifaceted intricacies of the Na+-Cl- cotransporter, a highly regulated key effector in the control of hydromineral homeostasis

The Na+-Cl- cotransporter (NCC; SLC12A3) is a highly regulated integral membrane protein that is known to exist as three splice variants in primates. Its primary role in the kidney is to mediate the cosymport of Na+ and Cl- across the apical membrane of the distal convoluted tubule. Through this role and the involvement of other ion transport systems, NCC allows the systemic circulation to reclaim a fraction of the ultrafiltered Na+, K+, Cl-, and Mg+ loads in exchange for Ca2+ and [Formula: see text]. The physiological relevance of the Na+-Cl- cotransport mechanism in humans is illustrated by several abnormalities that result from NCC inactivation through the administration of thiazides or in the setting of hereditary disorders. The purpose of the present review is to discuss the molecular mechanisms and overall roles of Na+-Cl- cotransport as the main topics of interest. On reading the narrative proposed, one will realize that the knowledge gained in regard to these themes will continue to progress unrelentingly no matter how refined it has now become.

Variants in tubule epithelial regulatory elements mediate most heritable differences in human kidney function

Kidney disease is highly heritable; however, the causal genetic variants, the cell types in which these variants function, and the molecular mechanisms underlying kidney disease remain largely unknown. To identify genetic loci affecting kidney function, we performed a GWAS using multiple kidney function biomarkers and identified 462 loci. To begin to investigate how these loci affect kidney function, we generated single-cell chromatin accessibility (scATAC-seq) maps of the human kidney and identified candidate cis-regulatory elements (cCREs) for kidney podocytes, tubule epithelial cells, and kidney endothelial, stromal, and immune cells. Kidney tubule epithelial cCREs explained 58% of kidney function SNP-heritability and kidney podocyte cCREs explained an additional 6.5% of SNP-heritability. In contrast, little kidney function heritability was explained by kidney endothelial, stromal, or immune cell-specific cCREs. Through functionally informed fine-mapping, we identified putative causal kidney function variants and their corresponding cCREs. Using kidney scATAC-seq data, we created a deep learning model (which we named ChromKid) to predict kidney cell type-specific chromatin accessibility from sequence. ChromKid and allele specific kidney scATAC-seq revealed that many fine-mapped kidney function variants locally change chromatin accessibility in tubule epithelial cells. Enhancer assays confirmed that fine-mapped kidney function variants alter tubule epithelial regulatory element function. To map the genes which these regulatory elements control, we used CRISPR interference (CRISPRi) to target these regulatory elements in tubule epithelial cells and assessed changes in gene expression. CRISPRi of enhancers harboring kidney function variants regulated NDRG1 and RBPMS expression. Thus, inherited differences in tubule epithelial NDRG1 and RBPMS expression may predispose to kidney disease in humans. We conclude that genetic variants affecting tubule epithelial regulatory element function account for most SNP-heritability of human kidney function. This work provides an experimental approach to identify the variants, regulatory elements, and genes involved in polygenic disease.

Human pluripotent stem cell-derived kidney organoids reveal tubular epithelial pathobiology of heterozygous HNF1B-associated dysplastic kidney malformations

Hepatocyte nuclear factor 1B (HNF1B) encodes a transcription factor expressed in developing human kidney epithelia. Heterozygous HNF1B mutations are the commonest monogenic cause of dysplastic kidney malformations (DKMs). To understand their pathobiology, we generated heterozygous HNF1B mutant kidney organoids from CRISPR-Cas9 gene-edited human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) reprogrammed from a family with HNF1B-associated DKMs. Mutant organoids contained enlarged malformed tubules displaying deregulated cell turnover. Numerous genes implicated in Mendelian kidney tubulopathies were downregulated, and mutant tubules resisted the cyclic AMP (cAMP)-mediated dilatation seen in controls. Bulk and single-cell RNA sequencing (scRNA-seq) analyses indicated abnormal Wingless/Integrated (WNT), calcium, and glutamatergic pathways, the latter hitherto unstudied in developing kidneys. Glutamate ionotropic receptor kainate type subunit 3 (GRIK3) was upregulated in malformed mutant nephron tubules and prominent in HNF1B mutant fetal human dysplastic kidney epithelia. These results reveal morphological, molecular, and physiological roles for HNF1B in human kidney tubule differentiation and morphogenesis illuminating the developmental origin of mutant-HNF1B-causing kidney disease.

The Phenotypic Variability Associated with Hepatocyte Nuclear Factor 1B Genetic Defects Poses Challenges in Both Diagnosis and Therapy

The evolving landscape of clinical genetics is becoming increasingly relevant in the field of nephrology. HNF1B-associated renal disease presents with a diverse array of renal and extrarenal manifestations, prominently featuring cystic kidney disease and diabetes mellitus. For the genetic analyses, whole exome sequencing (WES) and multiplex ligation-dependent probe amplification (MLPA) were performed. Bioinformatics analysis was performed with Ingenuity Clinical Insights software (Qiagen). The patient's electronic record was utilized after receiving informed consent. In this report, we present seven cases of HNF1B-associated kidney disease, each featuring distinct genetic abnormalities and displaying diverse extrarenal manifestations. Over 12 years, the mean decline in eGFR averaged -2.22 ± 0.7 mL/min/1.73 m2. Diabetes mellitus was present in five patients, kidney dysplastic lesions in six patients, pancreatic dysplasia, hypomagnesemia and abnormal liver function tests in three patients each. This case series emphasizes the phenotypic variability and the fast decline in kidney function associated with HNF-1B-related disease. Additionally, it underscores that complex clinical presentations may have a retrospectively straightforward explanation through the use of diverse genetic analytical tools.

Genetic and Epigenetic Associations with Post-Transplant Diabetes Mellitus

Post-transplant diabetes mellitus (PTDM) is a common complication of solid organ transplantation. PTDM prevalence varies due to different diabetes definitions. Consensus guidelines for the diagnosis of PTDM have been published based on random blood glucose levels, glycated hemoglobin (HbA1c), and oral glucose tolerance test (OGTT). The task of diagnosing PTDM continues to pose challenges, given the potential for diabetes to manifest at different time points after transplantation, thus demanding constant clinical vigilance and repeated testing. Interpreting HbA1c levels can be challenging after renal transplantation. Pre-transplant risk factors for PTDM include obesity, sedentary lifestyle, family history of diabetes, ethnicity (e.g., African-Caribbean or South Asian ancestry), and genetic risk factors. Risk factors for PTDM include immunosuppressive drugs, weight gain, hepatitis C, and cytomegalovirus infection. There is also emerging evidence that genetic and epigenetic variation in the organ transplant recipient may influence the risk of developing PTDM. This review outlines many known risk factors for PTDM and details some of the pathways, genetic variants, and epigenetic features associated with PTDM. Improved understanding of established and emerging risk factors may help identify people at risk of developing PTDM and may reduce the risk of developing PTDM or improve the management of this complication of organ transplantation.

A Case of Chromosome 17q12 Deletion Syndrome with Type 2 Mayer-Rokitansky-Küster-Hauser Syndrome and Maturity-Onset Diabetes of the Young Type 5

Chromosome 17q12 deletion syndrome (OMIM #614527) is a rare genetic disorder associated with a heterozygous 1.4-1.5 Mb deletion at chromosome 17q12, leading to a spectrum of clinical manifestations, including kidney abnormalities, neurodevelopmental delay, maturity-onset diabetes of the young type 5 (MODY5), and Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome. We present the case of a 14-year-old Korean female diagnosed with chromosome 17q12 deletion syndrome, confirmed by chromosomal microarray analysis. The patient exhibited MODY5 with pancreatic agenesis, MRKH syndrome, dysmorphic facial features, developmental delay, kidney rotation anomaly, portal vein thrombosis with liver hypoplasia, short stature, and scoliosis. Management involved the initiation of multiple daily insulin injections for diabetes control, gynecological evaluation for MRKH syndrome, and multidisciplinary care for associated complications. This case highlights the complexity and varied organ involvement in chromosome 17q12 deletion syndrome. A comprehensive and multidisciplinary approach is crucial for the management of affected individuals, including regular monitoring, tailored interventions across various medical specialties, and providing psychosocial support.

Late-onset Cholestasis with Paucity of Portal Area Secondary to HNF1β Deficiency in Adulthood: A Case Report

Hepatocyte nuclear factor 1β (HNF1β) is essential for biliary development, while its genetic defect triggers the dysplasia of interlobular bile ducts, leading to life-threatening hepatitis and cholestasis. To date, this disorder has mainly been documented in neonates. Here, we report a case of cholestasis in an adult patient caused by a de novo HNF1β mutation. A liver biopsy revealed remarkable shrinkage of the portal area accompanied by a decrease or absence of interlobular bile ducts, veins, and arteries in the portal area. Our case showed that an HNF1β defect could induce late-onset cholestasis with paucity of the portal area in adulthood.

Semaglutide as a potential therapeutic alternative for HNF1B-MODY: a case study

Maturity-onset diabetes of the young (MODY) is a grouping of monogenic disorders. It is characterized by dominantly inherited, non-insulin-dependent diabetes. MODY is relatively rare, encompassing up to 3.5% in those diagnosed under 30 years of age. Specific types are most commonly treated with sulfonylurea, particularly those identified as HNF4A-MODY and HNF1A-MODY. HNF1B-MODY is another type that is most frequently managed with insulin therapy but lacks a defined precision treatment. We present an 18-year-old, non-obese female patient diagnosed with HNF1B-MODY. She displays complete gene deletion, a renal cyst, and hypomagnesemia. Her treatment plan includes both long- and short-acting insulin, though she frequently encountered hypoglycemia and hyperglycemia. Semaglutide, a GLP-1RA, was administered weekly over 4 months. The patient's glucose level was continuously tracked using Dexcom's Continuous Glucose Monitoring system. The data suggested a notable improvement in her condition: time-in-range (TIR) increased from 70% to 88%, with some days achieving 100%, and the frequency of hypoglycemic episodes, indicated by time-below-range values, fell from 5% to 1%. The time-above-range values also dropped from 25% to 10%, and her HbA1c levels declined from 7% to 5.6%. During the semaglutide therapy, we were able to discontinue her insulin treatment. Additionally, her body mass index (BMI) was reduced from 24.1 to 20.1 kg/m2. However, the semaglutide treatment was halted after 4 months due to side effects such as nausea, vomiting, and reduced appetite. Other contributing factors included exam stress and a COVID-19 infection, which forced a switch back to insulin. Her last recorded HbA1c level under exclusive insulin therapy rose to 7.1%, and her BMI increased to 24.9 kg/m2. In conclusion, semaglutide could potentially replace insulin to improve glucose variability, TIR, and HbA1c in patients with HNF1B-MODY. However, more extensive studies are required to confirm its long-term safety and efficacy.

Large Kidney Cysts in HNF1B Nephropathy Mimicking Autosomal Dominant Polycystic Kidney Disease

Rationale

Hepatocyte nuclear factor 1 beta (HNF1B) nephropathy is a rare autosomal dominant monogenic kidney disease. We present a case mimicking autosomal dominant polycystic kidney disease (ADPKD), highlighting the phenotypic heterogeneity of HNF1B-related disease.

Presenting concerns of the patient

A 37-year-old man presented with hypertensive urgency, accompanied by flank pain and abdominal distension. Despite the absence of familial kidney disease, imaging revealed large bilateral kidney cysts resembling ADPKD.

Diagnosis

We initially suspected de novo ADPKD. However, negative genetic testing results for PKD1 and PKD2 led to a 43-gene cystic kidney sequencing panel which identified a deletion encompassing the entire HNF1B gene.

Intervention

To alleviate discomfort caused by the kidney cysts, ultrasound-guided aspiration and foam sclerotherapy were performed. Tolvaptan, used for treating high-risk ADPKD, was not prescribed after confirming the diagnosis was HNF1B nephropathy.

Outcomes

A diagnosis of HNF1B nephropathy was reached following gene panel testing. Abdominal symptoms improved following cyst aspiration and foam sclerotherapy.

Novel findings

HNF1B nephropathy has a variable presentation but can lead to cysts appearing like ADPKD. A 43-gene cystic kidney sequencing panel identified the diagnosis in this uncertain case.

Renal and extra-renal phenotypes in a fetus with a de novo pathogenic variant in the HNF1B gene

We report a fetus with prenatal ultrasound at 21 gestational weeks showing left cystic renal dysplasia with subcapsular cysts and echogenic parenchyma, right echogenic kidney with absent corticomedullary differentiation, and left congenital diaphragmatic hernia (CDH) with bowel herniation, with intestinal atresia (IA) found on postmortem examination. Whole genome sequencing of fetal blood DNA revealed a heterozygous pathogenic variant c.344 + 2 T>G in the HNF1B gene (NM_000458). Sanger sequencing of the parental samples suggested that it arose de novo in the fetus. HNF1B-associated disorders affect multiple organs with significant phenotypic heterogeneity. In pediatric and adult patients, renal cystic disease and cystic dysplasia are the dominant phenotypes. In prenatal settings, renal anomaly is also the most common presentation, typically with bilateral hyperechogenic kidneys. Our case presented with two uncommon extra-renal phenotypes of CDH and IA besides the typical bilateral cystic renal dysplasia. This association has been reported in fetuses with 17q12 microdeletion but not with HNF1B point mutation. Our case is the first prenatal report of such an association and highlights the possible causal relationship of HNF1B defects with CDH and IA in addition to the typical renal anomalies.

Reversed cortico-medullary differentiation in the fetal and neonatal kidneys: an indicator of poor prognosis?

BACKGROUND

Bilateral reversed cortico-medullary differentiation is rarely observed on fetal or neonatal renal ultrasound and is therefore a diagnostic challenge.

OBJECTIVE

Our purpose was to widen the differential diagnoses of fetal and neonatal nephropathies introducing reversed cortico-medullary differentiation as a clue either on obstetric US or during follow-up of hyperechoic kidneys in order to improve the management of such rare clinical situations.

MATERIALS AND METHODS

We retrospectively reviewed the US images of 11 patients showing bilateral reversed cortico-medullary differentiation on prenatal examination or in which this pattern developed postnatally in the follow-up of fetal hyperechoic kidneys. For each patient, a precise diagnosis was established either on clinical assessment or, when available, on histological or genetic findings.

RESULTS

Six fetuses displayed bilateral reversed cortico-medullary differentiation on obstetric examination, and the pattern persisted throughout pregnancy. In the five other fetuses, the kidneys appeared initially homogeneously hyperechoic; this evolved into reversed cortico-medullary differentiation during the third trimester in two cases and shortly after birth in three cases. Two pregnancies were terminated because of estimated poor prognosis. In the nine surviving neonates, four died of renal failure in the post-natal period. The clinical evolution was more favorable in the remaining five newborns.

CONCLUSIONS

Six different diagnoses were established in patients presenting with a reversed cortico-medullary differentiation renal pattern. This finding was associated with poor outcome in six cases. An acute prenatal diagnosis of reversed cortico-medullary differentiation improves pre- and postnatal work-up and guides counseling and genetic testing.

Mosaic loss of Y chromosome is associated with aging and epithelial injury in chronic kidney disease

BACKGROUND

Mosaic loss of Y chromosome (LOY) is the most common chromosomal alteration in aging men. Here, we use single-cell RNA and ATAC sequencing to show that LOY is present in the kidney and increases with age and chronic kidney disease.

RESULTS

The likelihood of a cell having LOY varies depending on its location in the nephron. Cortical epithelial cell types have a greater proportion of LOY than medullary or glomerular cell types, which may reflect their proliferative history. Proximal tubule cells are the most abundant cell type in the cortex and are susceptible to hypoxic injury. A subset of these cells acquires a pro-inflammatory transcription and chromatin accessibility profile associated with expression of HAVCR1, VCAM1, and PROM1. These injured epithelial cells have the greatest proportion of LOY and their presence predicts future kidney function decline. Moreover, proximal tubule cells with LOY are more likely to harbor additional large chromosomal gains and express pro-survival pathways. Spatial transcriptomics localizes injured proximal tubule cells to a pro-fibrotic microenvironment where they adopt a secretory phenotype and likely communicate with infiltrating immune cells.

CONCLUSIONS

We hypothesize that LOY is an indicator of increased DNA damage and potential marker of cellular senescence that can be applied to single-cell datasets in other tissues.

Japanese 17q12 Deletion Syndrome with Complex Clinical Manifestations

17q12 deletion syndrome is a rare chromosomal anomaly with variable phenotypes, caused by the heterozygous deletion of chromosome 17q12. We herein report a 35-year-old Japanese patient with chromosomal 17q12 deletion syndrome identified by de novo deletion of the 1.46 Mb segment at the 17q12 band by genetic analyses. He exhibited a wide range of phenotypes, such as maturity-onset diabetes of the young (MODY) type 5, structural or functional abnormalities of the kidney, liver, and pancreas; facial dysmorphic features, electrolyte disorders; keratoconus, and acquired perforating dermatosis. This case report provides valuable resources concerning the clinical spectrum of rare 17q12 deletion syndrome.

Genetic perspectives on childhood monogenic diabetes: Diagnosis, management, and future directions

Monogenic diabetes is caused by one or even more genetic variations, which may be uncommon yet have a significant influence and cause diabetes at an early age. Monogenic diabetes affects 1 to 5% of children, and early detection and gene-tically focused treatment of neonatal diabetes and maturity-onset diabetes of the young can significantly improve long-term health and well-being. The etiology of monogenic diabetes in childhood is primarily attributed to genetic variations affecting the regulatory genes responsible for beta-cell activity. In rare instances, mutations leading to severe insulin resistance can also result in the development of diabetes. Individuals diagnosed with specific types of monogenic diabetes, which are commonly found, can transition from insulin therapy to sulfonylureas, provided they maintain consistent regulation of their blood glucose levels. Scientists have successfully devised materials and methodologies to distinguish individuals with type 1 or 2 diabetes from those more prone to monogenic diabetes. Genetic screening with appropriate findings and interpretations is essential to establish a prognosis and to guide the choice of therapies and management of these interrelated ailments. This review aims to design a comprehensive literature summarizing genetic insights into monogenetic diabetes in children and adolescents as well as summarizing their diagnosis and mana-gement.

Diagnostic Yield and Benefits of Whole Exome Sequencing in CAKUT Patients Diagnosed in the First Thousand Days of Life

Introduction

Congenital anomalies of the kidney and urinary tract (CAKUT) are the predominant cause of chronic kidney disease (CKD) and the need for kidney replacement therapy (KRT) in children. Although more than 60 genes are known to cause CAKUT if mutated, genetic etiology is detected, on average, in only 16% of unselected CAKUT cases, making genetic testing unproductive.

Methods

Whole exome sequencing (WES) was performed in 100 patients with CAKUT diagnosed in the first 1000 days of life with CKD stages 1 to 5D/T. Variants in 58 established CAKUT-associated genes were extracted, classified according to the American College of Medical Genetics and Genomics guidelines, and their translational value was assessed.

Results

In 25% of these mostly sporadic patients with CAKUT, a rare likely pathogenic or pathogenic variant was identified in 1 or 2 of 15 CAKUT-associated genes, including GATA3, HNF1B, LIFR, PAX2, SALL1, and TBC1D1. Of the 27 variants detected, 52% were loss-of-function and 18.5% de novo variants. The diagnostic yield was significantly higher in patients requiring KRT before 3 years of age (43%, odds ratio 2.95) and in patients with extrarenal features (41%, odds ratio 3.5) compared with patients lacking these criteria. Considering that all affected genes were previously associated with extrarenal complications, including treatable conditions, such as diabetes, hyperuricemia, hypomagnesemia, and hypoparathyroidism, the genetic diagnosis allowed preventive measures and/or early treatment in 25% of patients.

Conclusion

WES offers significant advantages for the diagnosis and management of patients with CAKUT diagnosed before 3 years of age, especially in patients who require KRT or have extrarenal anomalies.

The genetics and pathogenesis of CAKUT

Congenital anomalies of the kidney and urinary tract (CAKUT) comprise a large variety of malformations that arise from defective kidney or urinary tract development and frequently lead to kidney failure. The clinical spectrum ranges from severe malformations, such as renal agenesis, to potentially milder manifestations, such as vesicoureteral reflux. Almost 50% of cases of chronic kidney disease that manifest within the first three decades of life are caused by CAKUT. Evidence suggests that a large number of CAKUT are genetic in origin. To date, mutations in ~54 genes have been identified as monogenic causes of CAKUT, contributing to 12-20% of the aetiology of the disease. Pathogenic copy number variants have also been shown to cause CAKUT and can be detected in 4-11% of patients. Furthermore, environmental and epigenetic factors can increase the risk of CAKUT. The discovery of novel CAKUT-causing genes is challenging owing to variable expressivity, incomplete penetrance and variable genotype-phenotype correlation. However, such a discovery could ultimately lead to improvements in the accurate molecular genetic diagnosis, assessment of prognosis and multidisciplinary clinical management of patients with CAKUT, potentially including personalized therapeutic approaches.

The use of precision diagnostics for monogenic diabetes: a systematic review and expert opinion

BACKGROUND

Monogenic diabetes presents opportunities for precision medicine but is underdiagnosed. This review systematically assessed the evidence for (1) clinical criteria and (2) methods for genetic testing for monogenic diabetes, summarized resources for (3) considering a gene or (4) variant as causal for monogenic diabetes, provided expert recommendations for (5) reporting of results; and reviewed (6) next steps after monogenic diabetes diagnosis and (7) challenges in precision medicine field.

METHODS

Pubmed and Embase databases were searched (1990-2022) using inclusion/exclusion criteria for studies that sequenced one or more monogenic diabetes genes in at least 100 probands (Question 1), evaluated a non-obsolete genetic testing method to diagnose monogenic diabetes (Question 2). The risk of bias was assessed using the revised QUADAS-2 tool. Existing guidelines were summarized for questions 3-5, and review of studies for questions 6-7, supplemented by expert recommendations. Results were summarized in tables and informed recommendations for clinical practice.

RESULTS

There are 100, 32, 36, and 14 studies included for questions 1, 2, 6, and 7 respectively. On this basis, four recommendations for who to test and five on how to test for monogenic diabetes are provided. Existing guidelines for variant curation and gene-disease validity curation are summarized. Reporting by gene names is recommended as an alternative to the term MODY. Key steps after making a genetic diagnosis and major gaps in our current knowledge are highlighted.

CONCLUSIONS

We provide a synthesis of current evidence and expert opinion on how to use precision diagnostics to identify individuals with monogenic diabetes.

MODY5 and Serous Ovarian Carcinoma in 17q12 Recurrent Deletion Syndrome

Background/Objective

Maturity-onset diabetes of the young type 5 (MODY5) is caused by a hepatocyte nuclear factor 1β (HNF1β) gene mutation on chromosome 17q12. HNF1β mutations have also been found in ovarian clear cell carcinoma, whereas ovarian non-clear cell carcinoma expresses this mutation rarely. 17q12 recurrent deletion syndrome features include MODY5, urogenital anomalies, and psychiatric and neurodevelopmental disorders. This is a report of a patient with 17q12 recurrent deletion syndrome with MODY5, uterine abnormalities, and low-grade serous ovarian cancer.

Case Report

A 25-year-old woman with recently diagnosed stage IIIC low-grade serous ovarian carcinoma was evaluated at the endocrinology clinic for diabetes, which was diagnosed at the age of 12 years. C-peptide level was detectable and T1DM antibodies were negative. The mother had diabetes, partially septated uterus, and solitary kidney. Abdominal computed tomography showed pancreatic atrophy, ascites, omental and peritoneal nodularity, and calcifications. Laparoscopy revealed bicornuate uterus, 2 cervices, and vaginal septum. The patient underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy, lymph node dissection, and omentectomy. Chromosomal microarray analysis revealed a pathogenic ∼1.8 Mb loss of 17q12, denoted arr[hg19]17q12(34477479_36283807)x1.

Discussion

17q12deletion has been described as a susceptibility locus in some ovarian cancers. However, to our knowledge, predisposition to ovarian cancer as a feature of 17q12 recurrent deletion syndrome or MODY5 was not reported previously.

Conclusion

The disease association reported suggests that medical providers should periodically evaluate for ovarian cancer, gut, and urogenital abnormalities in individuals with MODY5. Likewise, individuals with diabetes plus urogenital tract abnormalities or 17q12deletion in an ovarian tumor should undergo genetic testing for MODY5.

A Systematic Review of the use of Precision Diagnostics in Monogenic Diabetes

Monogenic forms of diabetes present opportunities for precision medicine as identification of the underlying genetic cause has implications for treatment and prognosis. However, genetic testing remains inconsistent across countries and health providers, often resulting in both missed diagnosis and misclassification of diabetes type. One of the barriers to deploying genetic testing is uncertainty over whom to test as the clinical features for monogenic diabetes overlap with those for both type 1 and type 2 diabetes. In this review, we perform a systematic evaluation of the evidence for the clinical and biochemical criteria used to guide selection of individuals with diabetes for genetic testing and review the evidence for the optimal methods for variant detection in genes involved in monogenic diabetes. In parallel we revisit the current clinical guidelines for genetic testing for monogenic diabetes and provide expert opinion on the interpretation and reporting of genetic tests. We provide a series of recommendations for the field informed by our systematic review, synthesizing evidence, and expert opinion. Finally, we identify major challenges for the field and highlight areas for future research and investment to support wider implementation of precision diagnostics for monogenic diabetes.

Cystic kidney diseases in children

Cystic kidney disease comprises a broad group of heterogeneous diseases, which differ greatly in age at onset, disease manifestation, systemic involvement, disease progression, and long-term prognosis. As our understanding of these diseases continues to evolve and new treatment strategies continue to emerge, correctly differentiating and diagnosing these diseases becomes increasingly important. In this review, we aim to highlight the key features of the most relevant cystic kidney diseases, underscore important diagnostic characteristics of each disease, and present specific management options if applicable.

HNF1B-driven three-dimensional chromatin structure for molecular classification in pancreatic cancers

The molecular subtypes of pancreatic cancer (PC), either classical/progenitor-like or basal/squamous-like, are currently a major topic of research because of their direct association with clinical outcomes. Some transcription factors (TFs) have been reported to be associated with these subtypes. However, the mechanisms by which these molecular signatures of PCs are established remain unknown. Epigenetic regulatory processes, supported by dynamic changes in the chromatin structure, are essential for transcriptional profiles. Previously, we reported the importance of open chromatin profiles in the biological features and transcriptional status of PCs. Here, we aimed to analyze the relationships between three-dimensional (3D) genome structures and the molecular subtypes of human PCs using Hi-C analysis. We observed a correlation of the specific elements of 3D genome modules, including compartments, topologically associating domains, and enhancer-promoter loops, with the expression of related genes. We focused on HNF1B, a TF that is implicated in the progenitor subtype. Forced expression of HNF1B in squamous-type PC organoids induced the upregulation and downregulation of genes associated with progenitor and squamous subtypes, respectively. Long-range genomic interactions induced by HNF1B were accompanied by compartment modulation and H3K27ac redistribution. We also found that these HNF1B-induced changes in subtype-related gene expression required an intrinsically disordered region, suggesting a possible involvement of phase separation in compartment modulation. Thus, mapping of 3D structural changes induced by TFs, such as HNF1B, may become a useful resource for further understanding the molecular features of PCs.

Review of neurodevelopmental disorders in patients with HNF1B gene variations

This review investigates the association between neurodevelopmental disorders (NDD) and variations of the gene HNF1B. Heterozygous intragenetic mutations or heterozygous gene deletions (17q12 microdeletion syndrome) of HNF1B are the cause of a multi-system developmental disorder, termed renal cysts and diabetes syndrome (RCAD). Several studies suggest that in general, patients with genetic variation of HNF1B have an elevated risk for additional neurodevelopmental disorders, especially autism spectrum disorder (ASD) but a comprehensive assessment is yet missing. This review provides an overview including all available studies of patients with HNF1B mutation or deletion with comorbid NDD with respect to the prevalence of NDDs and in how they differ between patients with an intragenic mutation or 17q12 microdeletion. A total of 31 studies was identified, comprising 695 patients with variations in HNF1B, (17q12 microdeletion N = 416, mutation N = 279). Main results include that NDDs are present in both groups (17q12 microdeletion 25.2% vs. mutation 6.8%, respectively) but that patients with 17q12 microdeletions presented more frequently with any NDDs and especially with learning difficulties compared to patients with a mutation of HNF1B. The observed prevalence of NDDs in patients with HNF1B variations seems to be higher than in the general population, but the validity of the estimated prevalence must be deemed insufficient. This review shows that systematical research of NDDs in patients with HNF1B mutations or deletions is lacking. Further studies regarding neuropsychological characteristics of both groups are needed. NDDs might be a concomitant of HFN1B-related disease and should be considered in clinical routine and scientific reports.