Chromosome 17q12 microdeletions but not intragenic HNF1B mutations link developmental kidney disease and psychiatric disorder

Association between rare, genetic variants linked to autism and ultrasonography fetal anomalies in children with autism spectrum disorder

BACKGROUND

Recent evidence suggests that certain fetal anomalies detected upon prenatal ultrasound screenings are associated with autism spectrum disorder (ASD). In this cross-sectional study, we aimed to identify genetic variants associated with fetal ultrasound anomalies (UFAs) in children with ASD.

METHODS

The study included all children with ASD who are registered in the database of the Azrieli National Center of Autism and Neurodevelopment and for whom both prenatal ultrasound and whole exome sequencing (WES) data were available. We applied our in-house integrative bioinformatics pipeline, AutScore, to these WES data to prioritize rare, gene-disrupting variants (GDVs) probably contributing to ASD susceptibily. Univariate statistics and multivariable regression were used to assess the associations between UFAs and GDVs identified in these children.

RESULTS

The study sample comprised 126 children, of whom 43 (34.1%) had at least one UFA detected in the prenatal ultrasound scan. A total of 87 candidate ASD genetic variants were detected in 60 children, with 24 (40%) children carrying multiple variants. Children with UFAs were more likely to have loss-of-function (LoF) mutations (aOR = 2.55, 95%CI: 1.13-5.80). This association was particularly noticeable when children with structural anomalies or children with UFAs in their head and brain scans were compared to children without UFAs (any mutation: aOR = 8.28, 95%CI: 2.29-30.01; LoF: aOR = 5.72, 95%CI: 2.08-15.71 and any mutation: aOR = 6.39, 95%CI: 1.34-30.47; LoF: aOR = 4.50, 95%CI: 1.32-15.35, respectively). GDVs associated with UFAs were enriched in genes highly expressed across all tissues (aOR = 2.76, 95%CI: 1.14-6.68). There was a weak, but significant, correlation between the number of mutations and the number of abnormalities detected in the same children (r = 0.21, P = 0.016).

CONCLUSIONS

The results provide valuable insights into the potential genetic basis of prenatal organogenesis abnormalities associated with ASD and shed light on the complex interplay between genetic factors and fetal development.

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.

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.

Prenatal diagnosis and family analysis of 17q12 microdeletion syndrome with fetal renal abnormalities

Purpose

To analyze the prenatal diagnosis, parental verification, and pregnancy outcomes of three fetuses with 17ql2 microdeletion syndrome.

Methods

We retrospectively reviewed 46 singleton pregnancies with anomalies in the urinary system who underwent amniocentesis from Feb 2022 to October 2023 in the Prenatal Diagnosis Center of Lianyungang Maternal and Child Health Hospital. These fetuses were subjected to chromosomal microarray analysis (CMA) and/or trio whole-exome sequencing (Trio-WES). We specifically evaluated these cases' prenatal renal ultrasound findings and clinical characteristics of the affected parents.

Results

Three fetuses were diagnosed as 17q12 microdeletions, and the detection rate was 6.5% in fetuses with anomalies in the urinary system (3/46). The heterogeneous deletions range from 1.494 to 1.66 Mb encompassing the complete hepatocyte nuclear factor 1 homeobox B (HNF1B) gene. Fetuses with 17q12 deletion exhibited varied renal phenotypes. Moreover, the clinical phenotypes of the affected parents differed greatly in the two cases (case 2 and case 3) in which the deletion was inherited. For case 3, the mother manifested classic symptoms of 17q12 deletion syndrome as well as unreported characteristics, such as very high myopia.

Conclusion

Our findings demonstrate the necessity and significance of offering prenatal genetic testing when various renal anomalies are detected. In addition, our study broadens the phenotypic spectrum of 17q12 deletions. Most importantly, our findings may allow timely supportive genetic counseling and guidance for pregnancy in affected families, e.g., with the help of preimplantation genetic testing (PGT).

A Case of Diabetes Mellitus Type MODY5 as a Feature of 17q12 Deletion Syndrome

Maturity onset diabetes of the young (MODY) is characterized by noninsulin-dependent diabetes diagnosed before the age of 25 years with an autosomal dominant inheritance. Rare mutations in the hepatocyte nuclear factor-1-beta (HNF1B) gene produce a syndrome that resembles MODY. About half of patients diagnosed with MODY type 5 due to HNF1B variants, carry a whole gene deletion, known as 17q12 deletion syndrome. 17q12 deletion syndrome is a rare chromosomal anomaly and is typified by deletion of more than 15 genes, including HNF1B resulting in kidney abnormalities and renal cysts, a diabetes syndrome and neurodevelopmental or neuropsychiatric disorders. A 12-year-old girl was referred after high blood sugar was detected in the hospital where she presented with polyuria and polydipsia, which had persisted for one month. Her serum magnesium (Mg) level was low at 1.5 mg/dL (normal value 1.6-2.6) and glycated hemoglobin was 14% (normal value 3.6-5.8) concurrent with a c-peptide of 1.54 ng/mL (normal value 0.8-4). MODY5 was suspected but the NGS gene panel (ABCC8, BLK, CEL, GCK, HNF1A, HNF1B, HNF4A, INS, KCNJ11, KLF11, NEURODD1, PAX4, PDX1, RFX6, ZFP57, GLIS3, FOXP3, NEUROG3, G6PC2) did not identify any abnormality. During follow-up, her serum Mg remained low (1.2 mg/dL) together with elevated urinary Mg excretion at 172.5 mg/day. An HNF1B variant was again suspected in a patient with chronic hypomagnesemia with normal basal C peptide level. Abdominal computed tomography and magnetic resonance imaging revealed a 43 mm diameter, cystic lesion in the head of the pancreas, with agenesis of the pancreatic neck, trunk and tail. Genetic testing using a microarray analysis was subsequently performed and a heterozygous deletion at 17q12, including HNF1B, was detected. In case of clinical suspicion of HNF1B variants, further genetic examination using other techniques such as MLPA and CGH array may be required to detect the variant. This is because deletions and duplications may not be detected using next generation screening panel techniques.

State of the Science and Ethical Considerations for Preimplantation Genetic Testing for Monogenic Cystic Kidney Diseases and Ciliopathies

There is a broad phenotypic spectrum of monogenic polycystic kidney diseases (PKDs). These disorders often involve cilia-related genes and lead to the development of fluid-filled cysts and eventual kidney function decline and failure. Preimplantation genetic testing for monogenic (PGT-M) disorders has moved into the clinical realm. It allows prospective parents to avoid passing on heritable diseases to their children, including monogenic PKD. The PGT-M process involves embryo generation through in vitro fertilization, with subsequent testing of embryos and selective transfer of those that do not harbor the specific disease-causing variant(s). There is a growing body of literature supporting the success of PGT-M for autosomal-dominant and autosomal-recessive PKD, although with important technical limitations in some cases. This technology can be applied to many other types of monogenic PKD and ciliopathies despite the lack of existing reports in the literature. PGT-M for monogenic PKD, like other forms of assisted reproductive technology, raises important ethical questions. When considering PGT-M for kidney diseases, as well as the potential to avoid disease in future generations, there are regulatory and ethical considerations. These include limited government regulation and unstandardized consent processes, potential technical errors, high cost and equity concerns, risks associated with pregnancy for mothers with kidney disease, and the impact on all involved in the process, including the children who were made possible with this technology.

Hepatocyte nuclear factor 1B deletion, but not intragenic mutation, might be more susceptible to hypomagnesemia

AIMS

HNF1B syndrome is caused by defects in the hepatocyte nuclear factor 1B (HNF1B) gene, which leads to maturity-onset diabetes of the young type 5 and congenital organ malformations. This study aimed to identify a gene defect in a patient presenting with diabetes and severe diarrhea, while also analyzing the prevalence of hypomagnesemia and its correlation with the HNF1B genotype.

MATERIALS AND METHODS

Whole exome sequencing was used to identify responsible point mutations and small indels in the proband and their family members. Multiplex ligation-dependent probe amplification was carried out to identify HNF1B deletions. Furthermore, an analysis of published data on 539 cumulative HNF1B cases, from 29 literature sources, was carried out to determine the correlation between the HNF1B genotype and the phenotype of serum magnesium status.

RESULTS

Using multiplex ligation-dependent probe amplification, we identified a de novo heterozygous HNF1B deletion in the patient, who showed dorsal pancreas agenesis and multiple kidney cysts, as detected by magnetic resonance imaging. Magnesium supplementation effectively alleviated the symptoms of diarrhea. Hypomagnesemia was highly prevalent in 192 out of 354 (54.2%) patients with HNF1B syndrome. Compared with patients with intragenic mutations, those with HNF1B deletions were more likely to suffer from hypomagnesemia, with an odds ratio of 3.1 (95% confidence interval 1.8-5.4).

CONCLUSIONS

Hypomagnesemia is highly prevalent in individuals with HNF1B syndrome, and those with HNF1B deletion are more susceptible to developing hypomagnesemia compared with those with intragenic mutations. The genotype-phenotype associations in HNF1B syndrome have significant implications for endocrinologists in terms of genotype detection, treatment decisions and prognosis assessment.

A Role for Genetic Modifiers in Tubulointerstitial Kidney Diseases

With the increased availability of genomic sequencing technologies, the molecular bases for kidney diseases such as nephronophthisis and mitochondrially inherited and autosomal-dominant tubulointerstitial kidney diseases (ADTKD) has become increasingly apparent. These tubulointerstitial kidney diseases (TKD) are monogenic diseases of the tubulointerstitium and result in interstitial fibrosis and tubular atrophy (IF/TA). However, monogenic inheritance alone does not adequately explain the highly variable onset of kidney failure and extra-renal manifestations. Phenotypes vary considerably between individuals harbouring the same pathogenic variant in the same putative monogenic gene, even within families sharing common environmental factors. While the extreme end of the disease spectrum may have dramatic syndromic manifestations typically diagnosed in childhood, many patients present a more subtle phenotype with little to differentiate them from many other common forms of non-proteinuric chronic kidney disease (CKD). This review summarises the expanding repertoire of genes underpinning TKD and their known phenotypic manifestations. Furthermore, we collate the growing evidence for a role of modifier genes and discuss the extent to which these data bridge the historical gap between apparently rare monogenic TKD and polygenic non-proteinuric CKD (excluding polycystic kidney disease).

Pregnancy outcome with maternal HNF1B gene mutations and 17q12 deletions

There is an increasing body of literature regarding monogenic diabetes, particularly the more common forms of glucokinase and HNF1-alpha mutations (MODY2 and MODY3). There is relatively little published literature regarding rarer mutations. HNF1-beta mutations and 17q12 deletions may be associated with a broad range of organ dysfunction, renal disease and diabetes in particular resulting in high-risk pregnancies. This manuscript describes pregnancy outcomes in a woman with an HNF1-beta mutation and 2 women with an HNF1B/17q12 deletion and reviews the previously published literature. It highlights the significant rate of adverse maternal and fetal outcomes, and the maternal features suggestive of the diagnosis which should be considered in preconception counselling.

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.

Potter Deformation Sequence Caused by 17q12 Deletion: A Lethal Constellation

17q12 deletion syndrome causes developmental abnormalities of the kidneys, pancreas, genital tract, and neurodevelopment, and it has a wide range of phenotypes ranging from fetal demise to normal adulthood with minimal renal impairment. Here we describe a rare case of 17q12 deletion diagnosed prenatally, complicated by anhydramnios and Potter sequence. The baby was born but necessitated life-saving interventions due to pulmonary and renal insufficiency and ultimately succumbed to multi-organ failure. We present full autopsy results describing findings linked to 17q12 deletion, including severe bilateral multicystic renal dysplasia, pancreatic hypoplasia, and cysts adjacent to the Fallopian tubes. We also describe pulmonary hypoplasia and Potter facies as consequences of anhydramnios. We correlate these findings to our current understanding of molecular signals altered by 17q12 deletion, notably affecting HNF1B and LHX1 genes, which are known to mediate renal and genitourinary tract development.

17q12 deletion syndrome mouse model shows defects in craniofacial, brain and kidney development, and glucose homeostasis

17q12 deletion (17q12Del) syndrome is a copy number variant (CNV) disorder associated with neurodevelopmental disorders and renal cysts and diabetes syndrome (RCAD). Using CRISPR/Cas9 genome editing, we generated a mouse model of 17q12Del syndrome on both inbred (C57BL/6N) and outbred (CD-1) genetic backgrounds. On C57BL/6N, the 17q12Del mice had severe head development defects, potentially mediated by haploinsufficiency of Lhx1, a gene within the interval that controls head development. Phenotypes included brain malformations, particularly disruption of the telencephalon and craniofacial defects. On the CD-1 background, the 17q12Del mice survived to adulthood and showed milder craniofacial and brain abnormalities. We report postnatal brain defects using automated magnetic resonance imaging-based morphometry. In addition, we demonstrate renal and blood glucose abnormalities relevant to RCAD. On both genetic backgrounds, we found sex-specific presentations, with male 17q12Del mice exhibiting higher penetrance and more severe phenotypes. Results from these experiments pinpoint specific developmental defects and pathways that guide clinical studies and a mechanistic understanding of the human 17q12Del syndrome. This mouse mutant represents the first and only experimental model to date for the 17q12 CNV disorder. This article has an associated First Person interview with the first author of the paper.

Multiomics analysis reveals that hepatocyte nuclear factor 1β regulates axon guidance genes in the developing mouse kidney

The transcription factor hepatocyte nuclear factor 1β (HNF-1β) is essential for normal development of the kidney and other epithelial organs. In the developing mouse kidney, HNF-1β is required for the differentiation and patterning of immature nephrons and branching morphogenesis of the ureteric bud (UB). Here, we used ChIP-sequencing (ChIP-seq) and RNA sequencing (RNA-seq) to identify genes that are regulated by HNF-1β in embryonic mouse kidneys. ChIP-seq revealed that HNF-1β binds to 8284 sites in chromatin from E14.5 mouse kidneys. Comparison with previous ATAC-seq and histone modification studies showed that HNF-1β binding peaks colocalized with open chromatin and epigenetic marks of transcriptional activation (H3K27 acetylation, H3K4 trimethylation, H3K4 monomethylation), indicating that the binding sites were functional. To investigate the relationship between HNF-1β binding and HNF-1β-dependent gene regulation, RNA-seq was performed on UB cells purified from wild-type and HNF-1β mutant embryonic kidneys. A total of 1632 genes showed reduced expression in HNF-1β-deficient UB cells, and 485 genes contained nearby HNF-1β binding sites indicating that they were directly activated by HNF-1β. Conversely, HNF-1β directly repressed the expression of 526 genes in the UB. Comparison with snATAC-seq analysis of UB-derived cells showed that both HNF-1β-dependent activation and repression correlated with chromatin accessibility. Pathway analysis revealed that HNF-1β binds near 68 axon guidance genes in the developing kidney. RNA-seq analysis showed that Nrp1, Sema3c, Sema3d, Sema6a, and Slit2 were activated by HNF-1β, whereas Efna1, Epha3, Epha4, Epha7, Ntn4, Plxna2, Sema3a, Sema4b, Slit3, Srgap1, Unc5c and Unc5d were repressed by HNF-1β. RNAscope in situ hybridization showed that Nrp1, Sema3c, Sema3d, Sema6a, and Slit2 were expressed in wild-type UB and were dysregulated in HNF-1β mutant UB. These studies show that HNF-1β directly regulates the expression of multiple axon guidance genes in the developing mouse kidney. Dysregulation of axon guidance genes may underlie kidney defects in HNF-1β mutant mice.

Recurrent 17q12 microduplications contribute to renal disease but not diabetes

BACKGROUND

17q12 microdeletion and microduplication syndromes present as overlapping, multisystem disorders. We assessed the disease phenotypes of individuals with 17q12 CNV in a population-based cohort.

METHODS

We investigated 17q12 CNV using microarray data from 450 993 individuals in the UK Biobank and calculated disease status associations for diabetes, liver and renal function, neurological and psychiatric traits.

RESULTS

We identified 11 17q12 microdeletions and 106 microduplications. Microdeletions were strongly associated with diabetes (p=2×10^-7) but microduplications were not. Estimated glomerular filtration rate (eGFR mL/min/1.73 m²) was consistently lower in individuals with microdeletions (p=3×10^-12) and microduplications (p=6×10^-25). Similarly, eGFR <60, including end-stage renal disease, was associated with microdeletions (p=2×10^-9, p<0.003) and microduplications (p=1×10^-9, p=0.009), respectively, highlighting sometimes substantially reduced renal function in each. Microduplications were associated with decreased fluid intelligence (p=3×10^-4). SNP association analysis in the 17q12 region implicated changes to HNF1B as causing decreased eGFR (NC_000017.11:g.37741642T>G, rs12601991, p=4×10^-21) and diabetes (NC_000017.11:g.37741165C>T, rs7501939, p=6×10^-17). A second locus within the region was also associated with fluid intelligence (NC_000017.11:g.36593168T>C, rs1005552, p=6×10^-9) and decreased eGFR (NC_000017.11:g.36558947T>C, rs12150665, p=4×10^-15).

CONCLUSION

We demonstrate 17q12 microdeletions but not microduplications are associated with diabetes in a population-based cohort, likely caused by HNF1B haploinsufficiency. We show that both 17q12 microdeletions and microduplications are associated with renal disease, and multiple genes within the region likely contribute to renal and neurocognitive phenotypes.

Mechanisms of ion transport regulation by HNF1β in the kidney: beyond transcriptional regulation of channels and transporters

Hepatocyte nuclear factor 1β (HNF1β) is a transcription factor essential for the development and function of the kidney. Mutations in and deletions of HNF1β cause autosomal dominant tubule interstitial kidney disease (ADTKD) subtype HNF1β, which is characterized by renal cysts, diabetes, genital tract malformations, and neurodevelopmental disorders. Electrolyte disturbances including hypomagnesemia, hyperuricemia, and hypocalciuria are common in patients with ADTKD-HNF1β. Traditionally, these electrolyte disturbances have been attributed to HNF1β-mediated transcriptional regulation of gene networks involved in ion transport in the distal part of the nephron including FXYD2, CASR, KCNJ16, and FXR. In this review, we propose additional mechanisms that may contribute to the electrolyte disturbances observed in ADTKD-HNF1β patients. Firstly, kidney development is severely affected in Hnf1b-deficient mice. HNF1β is required for nephron segmentation, and the absence of the transcription factor results in rudimentary nephrons lacking mature proximal tubule, loop of Henle, and distal convoluted tubule cluster. In addition, HNF1β is proposed to be important for apical-basolateral polarity and tight junction integrity in the kidney. Interestingly, cilia formation is unaffected by Hnf1b defects in several models, despite the HNF1β-mediated transcriptional regulation of many ciliary genes. To what extent impaired nephron segmentation, apical-basolateral polarity, and cilia function contribute to electrolyte disturbances in HNF1β patients remains elusive. Systematic phenotyping of Hnf1b mouse models and the development of patient-specific kidney organoid models will be essential to advance future HNF1β research.

Pathogenesis of Choledochal Cyst: Insights from Genomics and Transcriptomics

Choledochal cysts (CC) is characterized by extra- and/or intra-hepatic b\ile duct dilations. There are two main theories, “pancreaticobiliary maljunction” and “congenital stenosis of bile ducts” proposed for the pathogenesis of CC. Although family cases or CC associated with other anomalies have been reported, the molecular pathogenesis of CC is still poorly understood. Recent advances in transcriptomics and genomics analysis platforms have unveiled key expression signatures/genes/signaling pathways in the pathogenesis of human diseases including CC. This review summarizes insights from genomics and transcriptomics studies into the pathogenesis of CC, with the aim to improve (i) our understanding of its underlying complex pathomechanisms, and (ii) clinical management of different subtypes of CC, in particular their associated hepatic fibrotic change and their risk of malignancy transformation.

Phenotypic Variability of 17q12 Microdeletion Syndrome – Three Cases and Review of Literature

Chromosome 17q12 microdeletion syndrome is a contiguous gene deletion syndrome caused by an 1–2 Mb loss, characterized by multicystic dysplastic kidneys or other urinary system anomalies starting in utero, including autism or maturity-onset diabetes of the young in its postnatal phenotype. Here, we report on three cases (two prenatal and one postnatal) with distinct and novel clinical presentations as compared with a large number of reviewed patients, thus emphasizing the phenotypic variability of this syndrome and the consequent difficulties in genetic counselling. Prenatal hyperechogenic multicystic kidneys, as well as other urinary tract anomalies, should be considered a marker, therefore indicating the necessity of comprehensive genetic testing, and autism should also be acknowledged as a possible clinical presentation, postnatally.

Unusual manifestations of young woman with MODY5 based on 17q12 recurrent deletion syndrome

BACKGROUND

Maturity-onset diabetes of the young type 5 (MODY5) is a rare subtype of MODYs. It is caused by mutations of the hepatocyte nuclear factor 1 homeobox b gene (HNF1B). 17q12 recurrent deletion syndrome usually results in MODY5 because of the deletion of HNF1B. These patients often have other clinical manifestations besides diabetes. Refractory hypomagnesemia was a clue for further examination in this patient. But she lacked structural abnormalities of the genitourinary system and neurodevelopmental disorders that are common manifestations in patients with 17q12 recurrent deletion syndrome. Some atypical patients deserved attention.

CASE PRESENTATION

A 21-year-old young woman was admitted to our hospital for severe malnutrition and gastrointestinal symptoms. At age 20, she was diagnosed with type 2 diabetes mellitus (T2DM) and was administered oral antidiabetic drugs. Soon afterward, the patient discontinued the medication on her own accord and then went to the hospital again due to diabetic ketoacidosis. After insulin treatment, diabetic ketoacidosis was cured and blood glucose was controlled satisfactorily. But intractable nausea, vomiting, and persistent weight loss were stubborn. Further examination revealed that the patient had hypokalemia and hard rectification hypomagnesemia. Genetic testing revealed about 1.85 Mb heterozygous fragment deletion on chromosome 17 and deletion of exons 1-9 of HNF1B heterozygosity missing was approved. Finally, the patient was diagnosed MODY5.

DISCUSSION AND CONCLUSIONS

The 17q12 recurrent deletion syndrome is characterized by MODY5, structural or functional abnormalities of the kidney and urinary tract, and neurodevelopmental or neuropsychiatric disorders. This patient did not have any structural abnormalities of the genitourinary system and neuropsychiatric disorders, which is rare. She had experienced a period of misdiagnosis before being diagnosed with 17q12 recurrent deletion syndrome, and hypomagnesemia was an important clue for her diagnosis. Therefore, diabetic physicians should be alert to a special type of diabetes if patients have unexplained signs and symptoms. The absence of well-known features of HNF1B disease does not exclude MODY5.

Co-existing bipolar disease and 17q12 deletion: a rare case report

BACKGROUND

17q12 microdeletion syndrome is a rare autosomal dominant chromosomal anomaly, caused by the deletion of a 1.4 Mb-spanning DNA sequence on the long arm of chromosome 17. Herein, we report the first bipolar disease (BPD) case with a 1.6-Mb deletion in the 17q11.2-17q12 chromosome region.

MATERIALS AND METHODS

Physical examination of the case was performed. Karyotype and microarray analyses were performed for the case and the parents.

RESULTS

Physical examination revealed mild dysmorphic features such as high and forehead, full cheeks, slightly depressed nasal bridge and arched eyebrow. Chromosomal analysis of the patient revealed 46, XX, del(17)(q12) karyotype, and parents' karyotype were normal. In the microarray analysis of patient, 1.6 megabases deletion was detected in the 17q12 region [arr(hg19) 17q12 (34,611,352-36,248,918) ×1]. The microarray analysis of the mother was normal. The father's microarray showed 473 kilobases duplication in the 11p11.12 region.

CONCLUSION

Although 17q12 deletion syndrome has been associated with bipolar disorder, very few such cases have been described in the literature. Genetic counseling should be considered in patients with remarkable phenotype, complex symptomatology, neurodevelopmental disorder and additional conspicuous medical conditions.

OUP accepted manuscript

Multiple pieces of evidence support the prenatal predisposition of autism spectrum disorder (ASD). Nevertheless, robust data about abnormalities in foetuses later developing into children diagnosed with ASD are lacking. Prenatal ultrasound is an excellent tool to study abnormal foetal development as it is frequently used to monitor foetal growth and identify foetal anomalies throughout pregnancy. We conducted a retrospective case-sibling-control study of children diagnosed with ASD (cases); their own typically developing, closest-in-age siblings (TDS); and typically developing children from the general population (TDP), matched by year of birth, sex and ethnicity to investigate the association between ultrasonography foetal anomalies and ASD. The case group was drawn from all children diagnosed with ASD enrolled at the National Autism Research Center of Israel. Foetal ultrasound data from the foetal anatomy survey were obtained from prenatal ultrasound clinics of Clalit Health Services in southern Israel. The study comprised 659 children: 229 ASD, 201 TDS and 229 TDP. Ultrasonography foetal anomalies were found in 29.3% of ASD cases versus only 15.9% and 9.6% in the TDS and TDP groups [adjusted odds ratio (aOR) = 2.23, 95% confidence interval (CI) = 1.32-3.78, and aOR = 3.50, 95%CI = 2.07-5.91, respectively]. Multiple co-occurring ultrasonography foetal anomalies were significantly more prevalent among ASD cases. Ultrasonography foetal anomalies in the urinary system, heart, and head and brain were the most significantly associated with ASD diagnosis (aORUrinary = 2.08, 95%CI = 0.96-4.50 and aORUrinary = 2.90, 95%CI = 1.41-5.95; aORHeart = 3.72, 95%CI = 1.50-9.24 and aORHeart = 8.67, 95%CI = 2.62-28.63; and aORHead&Brain = 1.96, 95%CI = 0.72-5.30 and aORHead&Brain = 4.67, 95%CI = 1.34-16.24; versus TDS and TDP, respectively). ASD females had significantly more ultrasonography foetal anomalies than ASD males (43.1% versus 25.3%, P = 0.013) and a higher prevalence of multiple co-occurring ultrasonography foetal anomalies (15.7% versus 4.5%, P = 0.011). No sex differences were seen among TDS and TDP controls. ASD foetuses were characterized by a narrower head and a relatively wider ocular-distance versus TDP foetuses (ORBPD = 0.81, 95%CI = 0.70-0.94, and aOROcular distance = 1.29, 95%CI = 1.06-1.57). Ultrasonography foetal anomalies were associated with more severe ASD symptoms. Our findings shed important light on the multiorgan foetal anomalies associated with ASD.

Improving renal phenotype and evolving extra-renal features of 17q12 deletion encompassing the HNF1B gene

BACKGROUND

HNF1B deletion/intragenic mutations are the most commonly identified genetic cause of congenital anomalies of the kidney and urinary tract (CAKUT) suggested by fetal ultrasound findings such as: parenchymal hyperechogenicity, overt cystic changes or gross morphological urinary system (UT) abnormalities. The postnatal evolution of these 17q12 deletions encompassing the HNF1B gene-associated findings has not been assessed in depth.

METHODS

In this observational study, we present postnatal follow-up findings in 5 of 6 cases (one pregnancy was terminated on parental request) of fetal-onset cystic/hyperechogenic kidneys eventually diagnosed with 17q12 microdeletion encompassing the HNF1B gene between 2009 and 2017.

RESULTS

Complete normalization of kidney parenchymal abnormalities and of depressed neonatal renal function was observed in 4/5 and 5/5 patients within 2-4.9 years and 1.5-8 months, respectively. All 5 patients had preserved normal renal function at 3-11 years of follow-up. The evolving later-onset renal features included: hypomagnesemia, hyperuricemia, urinary tract infection (UTI), and bilateral grade 3-4 vesicoureteral reflux and bladder diverticula in 3, 3, 2, and 1 patient, respectively. HNF1B gene deletion-associated extra-renal manifestations with delayed presentation were global developmental delay/autistic spectrum disorder (ASD), rolandic-type seizures, overweight, and borderline fasting hyperglycemia observed in 1-2 patients each. Family history was positive for small-size or asymptomatic cystic kidneys with normal function, diabetes mellitus, seizures, and mental/psychiatric problems in 3/6 cases.

CONCLUSIONS

Fetal-onset HNF1B deletion-associated kidneys' parenchymal abnormalities confirmed postnatally with initially depressed renal function might undergo complete resolution within several years and few months, respectively. However, later-onset urinary tract, metabolic, and neurodevelopmental features of this mutation might appear over years. Therefore, genetic molecular evaluation/diagnosis and continuous follow-up for evolving features are mandatory in affected children.

Neurophysiological control of urinary bladder storage and voiding-functional changes through development and pathology

The effective storage of urine and its expulsion relies upon the coordinated activity of parasympathetic, sympathetic, and somatic innervations to the lower urinary tract (LUT). At birth, all mammalian neonates lack the ability to voluntary regulate bladder storage or voiding. The ability to control urinary bladder activity is established as connections to the central nervous system (CNS) form through development. The neural regulation of the LUT has been predominantly investigated in adult animal models where comparatively less is known about the neonatal and postnatal neurophysiological development that facilitate urinary continence. Furthermore, congenital neurological or anatomical defects can adversely affect both storage and voiding functions through postnatal development and into adulthood, leading to secondary conditions including vesicoureteral reflux, chronic urinary tract infections, and end-stage renal disease. Therefore, the aim of the review is to provide the current knowledge available on neurophysiological regulation of the LUT through pre- to postnatal development of human and animal models and the consequences of congenital anomalies that can affect LUT neural function.

Prenatal features of 17q12 microdeletion and microduplication syndromes: A retrospective case series

OBJECTIVE

To present the experience on prenatal features of 17q12 microdeletion and microduplication syndromes.

MATERIALS AND METHODS

Prenatal chromosomal microarray analysis (CMA) were conducted between January 2015 and December 2018 at a single Chinese tertiary medical centre. Information of cases identified with 17q12 microdeletion or microduplication syndromes were retrospectively collected. Foetal ultrasonographic findings were reviewed, and other information about the gestation week at diagnosis, inheritance and pregnancy outcomes were also included.

RESULTS

Ten pregnancies with 17q12 microdeletion and 4 with 17q12 microduplication were identified. The copy number variation (CNV) sizes were 1.39-1.94 Mb in the deleted cases and 1.42-1.48 Mb in the duplicated cases, respectively. All the duplicated and deleted regions included HNF1B and LHX1 genes. Most individuals with 17q12 deletion presented kidney anomalies (9/10), with renal hyperechogenicity being the most common finding (7/10). Fetuses with 17q12 duplication presented a wide phenotypic spectrum, including "double bubble" sign, structural anomalies of the heart and growth anomalies.

CONCLUSIONS

Our experience further demonstrated the high correlation between 17q12 microdeletion and renal anomalies especially hyperechogenic kidneys. Structural anomalies of the heart were newly identified phenotypes of 17q12 duplication during prenatal period. Besides, growth anomalies and duodenal atresia might be associated with the duplication.

Monogenic diabetes: a gateway to precision medicine in diabetes

Monogenic diabetes refers to diabetes mellitus (DM) caused by a mutation in a single gene and accounts for approximately 1%-5% of diabetes. Correct diagnosis is clinically critical for certain types of monogenic diabetes, since the appropriate treatment is determined by the etiology of the disease (e.g., oral sulfonylurea treatment of HNF1A/HNF4A-diabetes vs. insulin injections in type 1 diabetes). However, achieving a correct diagnosis requires genetic testing, and the overlapping of the clinical features of monogenic diabetes with those of type 1 and type 2 diabetes has frequently led to misdiagnosis. Improvements in sequencing technology are increasing opportunities to diagnose monogenic diabetes, but challenges remain. In this Review, we describe the types of monogenic diabetes, including common and uncommon types of maturity-onset diabetes of the young, multiple causes of neonatal DM, and syndromic diabetes such as Wolfram syndrome and lipodystrophy. We also review methods of prioritizing patients undergoing genetic testing, and highlight existing challenges facing sequence data interpretation that can be addressed by forming collaborations of expertise and by pooling cases.

Autism spectrum disorder and kidney disease

Neurodevelopmental impairments have been recognised as a major association of paediatric kidney disease and bladder dysfunction, presenting challenges to clinicians and families to provide reasonable adjustments in order to allow access to investigations and treatments. Autism spectrum disorder (ASD) is a common neurodevelopmental disorder characterised by impairments in social interaction/communication and repetitive sensory-motor behaviours. Mental health, learning and physical co-morbidities are common. There is emerging evidence that ASD and kidney disease have some overlaps with genetic copy number variants and environmental factors contributing to shared pathogenesis. Prevalence rates of ASD in kidney disease are currently not known. A high index of suspicion of underlying ASD is required when a young person presents with communication difficulties, anxiety or behaviour that challenges, which should then trigger referral for a neurodevelopmental and behavioural assessment. We discuss practical approaches for providing care, which include understanding methods of communication and sensory, behavioural and environmental adaptations.

Rare genetic causes of complex kidney and urological diseases

Although often considered a single-entity, chronic kidney disease (CKD) comprises many pathophysiologically distinct disorders that result in persistently abnormal kidney structure and/or function, and encompass both monogenic and polygenic aetiologies. Rare inherited forms of CKD frequently span diverse phenotypes, reflecting genetic phenomena including pleiotropy, incomplete penetrance and variable expressivity. Use of chromosomal microarray and massively parallel sequencing technologies has revealed that genomic disorders and monogenic aetiologies contribute meaningfully to seemingly complex forms of CKD across different clinically defined subgroups and are characterized by high genetic and phenotypic heterogeneity. Investigations of prevalent genomic disorders in CKD have integrated genetic, bioinformatic and functional studies to pinpoint the genetic drivers underlying their renal and extra-renal manifestations, revealing both monogenic and polygenic mechanisms. Similarly, massively parallel sequencing-based analyses have identified gene- and allele-level variation that contribute to the clinically diverse phenotypes observed for many monogenic forms of nephropathy. Genome-wide sequencing studies suggest that dual genetic diagnoses are found in at least 5% of patients in whom a genetic cause of disease is identified, highlighting the fact that complex phenotypes can also arise from multilocus variation. A multifaceted approach that incorporates genetic and phenotypic data from large, diverse cohorts will help to elucidate the complex relationships between genotype and phenotype for different forms of CKD, supporting personalized medicine for individuals with kidney disease.

From Theory to Reality: Establishing a Successful Kidney Genetics Clinic in the Outpatient Setting

Background

Genetic testing in nephrology is increasingly described in the literature and several groups have suggested significant clinical benefit. However, studies to date have described experience from established genetic testing centers or from externally funded research programs.

Methods

We established a de novo kidney genetics clinic within an academic adult general nephrology practice. Key features of this effort included a pipeline for internal referrals, flexible scheduling, close coordination between the nephrologist and a genetic counselor, and utilization of commercial panel-based testing. Over the first year, we examined the outcomes of genetic testing, the time to return of genetic testing, and out-of-pocket cost to patients.

Results

Thirty patients were referred and 23 were evaluated over the course of five clinic sessions. Nineteen patients underwent genetic testing with new diagnoses in nine patients (47%), inconclusive results in three patients (16%), and clearance for kidney donation in two patients (11%). On average, return of genetic results occurred 55 days (range 9-174 days) from the day of sample submission and the average out-of-pocket cost to patients was $155 (range $0-$1623).

Conclusions

We established a kidney genetics clinic, without a pre-existing genetics infrastructure or dedicated research funding, that identified a new diagnosis in approximately 50% of patients tested. This study provides a clinical practice model for successfully incorporating genetic testing into ambulatory nephrology care with minimal capital investment and limited financial effect on patients.

Maturity-Onset diabetes of the young type 5 treated with the glucagon-like peptide-1 receptor agonist: A case report

RATIONALE

Maturity-onset diabetes of the young type 5 (MODY 5) is a form of monogenic diabetes that is often accompanied by pancreatic dysfunction. To date, no cases of MODY 5 treated with glucagon-like peptide-1 receptor agonist (GLP-1RA) have been reported. We present the first case of MODY 5 treated with GLP-1RA.

PATIENT CONCERNS

A 17-year-old woman, with a history of being operated for congenital ileal atresia at birth, was admitted to our hospital due to hyperglycemia. She had been clinically diagnosed with type 1 diabetes 1 month prior, and administered 14 units of insulin glargine 300 U/mL per day.

DIAGNOSIS

She had hypopotassemia, hypomagnesaemia, pancreatic body, and tail defects, multiple renal cysts, and a family history of diabetes, and urogenital anomaly. Genetic testing revealed heterozygous deletion of hepatocyte nuclear transcription factor-1 beta, leading to the diagnosis of MODY 5.

INTERVENTIONS

The patient was treated with multiple daily insulin injections for 9 days (22 units/d) before administration of GLP-1RA, and then liraglutide was initiated.

OUTCOMES

Liraglutide treatment (0.6 mg/d) alone maintained the patient's glycated hemoglobin level below 7.0% for at least 12 months after discharge. A higher dose, 0.9 mg/d, of liraglutide was not tolerated by the patient due to nausea. Serum levels of C-peptide immunoreactivity were 1.15 ng/mL and 1.91 ng/mL, respectively, after 6 and 12 months of liraglutide therapy.

LESSONS

GLP-1RA might be effective at regulating glucose metabolism by utilizing residual pancreatic endocrine function in patients with MODY 5. Imaging and genetic screening were helpful in the diagnosis of MODY 5.

EARLY ONSET OF MODY5 DUE TO HAPLOINSUFFICIENCY OF HNF1B

Objective

To report 2 patients with haploinsufficiency of hepatic nuclear factor 1 homeobox B (HNF1B) that results in the onset of maturity onset diabetes of the young type 5 (MODY5) before 3 years of age.

Methods

We present 2 unusual patients with MODY5 that was diagnosed at 33 and 22 months of age, respectively. We describe the presentations, clinical course, and genetic tests of both patients, and lastly, we review the literature on the prevalence and the age of presentation of MODY5 both in children and in adult patients.

Results

The first patient had severe congenital renal dysplasia, and deoxyribonucleic acid microarray indicated the deletion of 17q12. Hemoglobin A1c (HbA1c) was obtained due to the concern of MODY5, and the initial level (6.6%, 49 mmol/mol) was abnormally elevated. The second patient had mild renal dysplasia and 17q12 deletion encompassing the HNF1B gene. Hyperglycemia was identified during an episode of respiratory illness. HbA1c (6.2%, 44 mmol/mol) level was abnormally elevated. Pancreatic autoantibodies were absent in both patients. Diet modification resulted in an improvement of HbA1c in both patients.

Conclusion

Our report highlights the importance of considering MODY5 in patients with congenital anomalies of kidney. Identification of children with MODY5 permits early management of hyperglycemia.

Role of transcription factor hepatocyte nuclear factor-1β in polycystic kidney disease

Hepatocyte nuclear factor-1β (HNF-1β) is a DNA-binding transcription factor that is essential for normal kidney development. Mutations of HNF1B in humans produce cystic kidney diseases, including renal cysts and diabetes, multicystic dysplastic kidneys, glomerulocystic kidney disease, and autosomal dominant tubulointerstitial kidney disease. Expression of HNF1B is reduced in cystic kidneys from humans with ADPKD, and HNF1B has been identified as a modifier gene in PKD. Genome-wide analysis of chromatin binding has revealed that HNF-1β directly regulates the expression of known PKD genes, such as PKHD1 and PKD2, as well as genes involved in PKD pathogenesis, including cAMP-dependent signaling, renal fibrosis, and Wnt signaling. In addition, a role of HNF-1β in regulating the expression of noncoding RNAs (microRNAs and long noncoding RNAs) has been identified. These findings indicate that HNF-1β regulates a transcriptional and post-transcriptional network that plays a central role in renal cystogenesis.

Prenatal diagnosis of HNF1B-associated renal cysts: Is there a need to differentiate intragenic variants from 17q12 microdeletion syndrome?

OBJECTIVE

17q12 microdeletions containing HNF1B and intragenic variants within this gene are associated with variable developmental, endocrine, and renal anomalies, often already noted prenatally as hyperechogenic/cystic kidneys. Here, we describe prenatal and postnatal phenotypes of seven individuals with HNF1B aberrations and compare their clinical and genetic data to those of previous studies.

METHODS

Prenatal sequencing and postnatal chromosomal microarray analysis were performed in seven individuals with renal and/or neurodevelopmental phenotypes. We evaluated HNF1B-related clinical features from 82 studies and reclassified 192 reported intragenic HNF1B variants.

RESULTS

In a prenatal case, we identified a novel in-frame deletion p.(Gly239del) within the HNF1B DNA-binding domain, a mutational hot spot as demonstrated by spatial clustering analysis and high computational prediction scores. The six postnatally diagnosed individuals harbored 17q12 microdeletions. Literature screening revealed variable reporting of HNF1B-associated clinical traits. Overall, both mutation groups showed a high phenotypic heterogeneity. The reclassification of all previously reported intragenic HNF1B variants provided an up-to-date overview of the mutational spectrum.

CONCLUSIONS

We highlight the value of prenatal HNF1B screening in renal developmental diseases. Standardized clinical reporting and systematic classification of HNF1B variants are necessary for a more accurate risk quantification of prenatal and postnatal clinical features, improving genetic counseling and prenatal decision making.

Case report: extreme coronary calcifications and hypomagnesemia in a patient with a 17q12 deletion involving HNF1B

Background

17q12 deletion syndrome encompasses a broad constellation of clinical phenotypes, including renal magnesium wasting, maturity-onset diabetes of the young (MODY), renal cysts, genitourinary malformations, and neuropsychiatric illness. Manifestations outside of the renal, endocrine, and nervous systems have not been well described.

Case presentation

We report a 62-year-old male referred to the Undiagnosed Diseases Program (UDP) at the National Institutes of Health (NIH) who presented with persistent hypermagnesiuric hypomagnesemia and was found to have a 17q12 deletion. The patient exhibited several known manifestations of the syndrome, including severe hypomagnesemia, renal cysts, diabetes and cognitive deficits. Coronary CT revealed extensive coronary calcifications, with a coronary artery calcification score of 12,427. Vascular calcifications have not been previously reported in this condition. We describe several physiologic mechanisms and a review of literature to support the expansion of the 17q12 deletion syndrome to include vascular calcification.

Conclusion

Extensive coronary and vascular calcifications may be an extension of the 17q12 deletion phenotype, particularly if hypomagnesemia and hyperparathyroidism are prevalent. In patients with 17q12 deletions involving HNF1B, hyperparathyroidism and hypomagnesemia may contribute to significant cardiovascular risk.

School level of children carrying a HNF1B variant or a deletion

The prevalence of neurological involvement in patients with a deletion of or a variant in the HNF1B gene remains discussed. The aim of this study was to investigate the neuropsychological outcomes in a large cohort of children carrying either a HNF1B whole-gene deletion or a disease-associated variant, revealed by the presence of kidney anomalies. The neuropsychological development-based on school level-of 223 children included in this prospective cohort was studied. Data from 180 children were available for analysis. Patients mean age was 9.6 years, with 39.9% of girls. Among these patients, 119 carried a HNF1B deletion and 61 a disease-associated variant. In the school-aged population, 12.7 and 3.6% of patients carrying a HNF1B deletion and a disease-associated variant had special educational needs, respectively. Therefore, the presence of a HNF1B deletion increases the risk to present with a neuropsychiatric involvement when compared with the general population. On the other hand, almost 90% of patients carrying a HNF1B disease-associated variant or deletion have a normal schooling in a general educational environment. Even if these findings do not predict the risk of neuropsychiatric disease at adulthood, most patients diagnosed secondary to kidney anomalies do not show a neurological outcome severe enough to impede standard schooling at elementary school. These results should be taken into account in prenatal counseling.

Autosomal dominant tubulointerstitial kidney disease

Autosomal dominant tubulointerstitial kidney disease (ADTKD) is a recently defined entity that includes rare kidney diseases characterized by tubular damage and interstitial fibrosis in the absence of glomerular lesions, with inescapable progression to end-stage renal disease. These diseases have long been neglected and under-recognized, in part due to confusing and inconsistent terminology. The introduction of a gene-based, unifying terminology led to the identification of an increasing number of cases, with recent data suggesting that ADTKD is one of the more common monogenic kidney diseases after autosomal dominant polycystic kidney disease, accounting for ~5% of monogenic disorders causing chronic kidney disease. ADTKD is caused by mutations in at least five different genes, including UMOD, MUC1, REN, HNF1B and, more rarely, SEC61A1. These genes encode various proteins with renal and extra-renal functions. The mundane clinical characteristics and lack of appreciation of family history often result in a failure to diagnose ADTKD. This Primer highlights the different types of ADTKD and discusses the distinct genetic and clinical features as well as the underlying mechanisms.

Association between the clinical presentation of congenital anomalies of the kidney and urinary tract (CAKUT) and gene mutations: an analysis of 66 patients at a single institution

BACKGROUND

The association between the clinical presentation of congenital anomalies of the kidney and urinary tract (CAKUT) and gene mutations has yet to be fully explored.

METHODS

In this retrospective cohort study, we examined patients with CAKUT who underwent gene analysis. The analysis was performed in patients with bilateral renal lesions, extrarenal complications, or a family history of renal disease. The data from the diagnosis, gene mutations, and other complications were analyzed.

RESULTS

In total, 66 patients with CAKUT were included. Of these, gene mutations were detected in 14 patients. Bilateral renal lesions were significantly related to the identification of gene mutations (p = 0.02), and no gene mutations were observed in patients with lower urinary tract obstruction (six patients). There was no significant difference in the rate of gene mutations between those with or without extrarenal complications (p = 0.76). The HNF1β gene mutation was identified in most of the patients with hypodysplastic kidney with multicystic dysplastic kidney (six of seven patients). There was no significant difference in the presence or absence of gene mutations with respect to the renal survival rate (log-rank test p = 0.53). The renal prognosis varied, but the differences were not statistically significant for any of the gene mutations.

CONCLUSIONS

CAKUT with bilateral renal lesions were significantly related to gene mutations. We recommend that CAKUT-related gene analysis be considered in cases of bilateral renal lesions. No gene mutations were observed in patients with lower urinary tract obstruction. The renal prognosis varied for each gene mutation.

HNF1B nephropathy has a slow-progressive phenotype in childhood-with the exception of very early onset cases: results of the German Multicenter HNF1B Childhood Registry

BACKGROUND

HNF1B gene mutations are an important cause of bilateral (cystic) dysplasia in children, complicated by chronic renal insufficiency. The clinical variability, the absence of genotype-phenotype correlations, and limited long-term data render counseling of affected families difficult.

METHODS

Longitudinal data of 62 children probands with genetically proven HNF1B nephropathy was obtained in a multicenter approach. Genetic family cascade screening was performed in 30/62 cases.

RESULTS

Eighty-seven percent of patients had bilateral dysplasia, 74% visible bilateral, and 16% unilateral renal cysts at the end of observation. Cyst development was non-progressive in 72% with a mean glomerular filtration rate (GFR) loss of - 0.33 ml/min/1.73m² per year (± 8.9). In patients with an increase in cyst number, the annual GFR reduction was - 2.8 ml/min/1.73m² (± 13.2), in the total cohort - 1.0 ml/min/1.73m² (±10.3). A subset of HNF1B patients differs from this group and develops end stage renal disease (ESRD) at very early ages < 2 years. Hyperuricemia (37%) was a frequent finding at young age (median 1 year), whereas hypomagnesemia (24%), elevated liver enzymes (21%), and hyperglycemia (8%) showed an increased incidence in the teenaged child. Genetic analysis revealed no genotype-phenotype correlations but a significant parent-of-origin effect with a preponderance of 81% of maternal inheritance in dominant cases.

CONCLUSIONS

In most children, HNF1B nephropathy has a non-progressive course of cyst development and a slow-progressive course of kidney function. A subgroup of patients developed ESRD at very young age < 2 years requiring special medical attention. The parent-of-origin effect suggests an influence of epigenetic modifiers in HNF1B disease.

Searching for mutations in the HNF1B gene in a Brazilian cohort with renal cysts and hyperglycemia

OBJECTIVE

To verify the presence of variants in HNF1B in a sample of the Brazilian population selected according to the presence of renal cysts associated with hyperglycemia.

SUBJECTS AND METHODS

We evaluated 28 unrelated patients with clinical suspicion of HNF1B mutation because of the concomitant presence of diabetes mellitus (DM) or prediabetes and renal cysts. Genotyping was accomplished using Sanger sequencing or multiplex ligation-dependent probe amplification (MLPA). In positive cases, available relatives were recruited.

RESULTS

We found two patients with HNF1B mutations. The first presented the variant p.Pro328Leufs*48(c.983delC) and had DM, renal cysts, and hypomagnesemia. The second presented a heterozygous whole gene deletion in HNF1B, DM, renal cysts, body and tail pancreatic agenesis, and hypomagnesemia; this alteration was also found in his two siblings and his father.

CONCLUSION

The recruitment of suspected cases of HNF1B gene mutations in Brazilians due to hyperglycemia and renal cysts presents two positive cases. Our cases contribute to the annotation of clinical and biochemical phenotypes of this rare form of maturity-onset diabetes of the young (MODY).

Tumor-suppressive activity of Hnf1β in Wilms' tumor

Hepatocyte nuclear factor 1β (HNF1β) is a transcription factor belonging to the HNF-1 family and has been implicated in a number of cancers, but its role in Wilms' tumor (nephroblastoma) has not been addressed. Here, we compared its expression between Wilms' tumor patient kidney tissue and adjacent tissue based on the Oncomine database ( www.oncomine.com ). Cell proliferation, apoptosis, migration, and HNF1β expression level were analyzed in Wilms' tumor-derived G401 cells. Using a variety of mouse tissues (lung, heart, kidney, etc.), we found that HNF1β is the highest expression in the kidneys. Oncomine analysis further demonstrated that HNF1β has a lower expression in Wilms' tumor tissue than in paracancerous tissues. Overexpression of HNF1β decreased cell proliferation and migration, but promoted cell apoptosis. Knockdown of HNF1β produced the opposite results. These results indicated that HNF1β may play important roles in kidney development and function, and its activation may negatively regulate Wilms' tumor progression.

Not only Alagille syndrome. Syndromic paucity of interlobular bile ducts secondary to HNF1β deficiency: a case report and literature review

BACKGROUND

paucity of interlobular bile ducts is an important observation at liver biopsy in the diagnostic work-up of neonatal cholestasis. To date, other than in the Alagille syndrome, syndromic paucity of interlobular bile ducts has been documented in four cholestatic neonates with HFN1β mutations. A syndromic phenotype, known as renal cysts and diabetes syndrome (RCAD), has been identified. This is usually characterized by a wide clinical spectrum, including renal cysts, maturity-onset diabetes of the young, exocrine pancreatic insufficiency, urogenital abnormalities and a not well established liver involvement. Herein we report a novel case of paucity of interlobular bile ducts due to an HFN1β defect.

CASE PRESENTATION

A 5-week-old boy was admitted to our department for cholestatic jaundice with increased gamma-glutamyl transpeptidase and an unremarkable clinical examination. He had been delivered by Caesarian section at 38 weeks' gestation from unrelated parents, with a birth weight of 2600 g (3rd percentile). Screening for cholestatic diseases, including Alagille syndrome, was negative except for a minor pulmonary artery stenosis at echocardiography and a doubt of a thoracic butterfly hemivertebra. The finding of hyperechogenic kidneys with multiple bilateral cortical cysts at ultrasound examination, associated with moderately impaired renal function with proteinuria, polyuria and metabolic acidosis, was suggestive of ciliopathy. A liver biopsy was performed revealing paucity of interlobular bile ducts, thus the diagnosis of Alagille syndrome was reconsidered. Although genetic tests for liver cholestatic diseases were performed with negative results for Alagille syndrome (JAG1 and NOTCH2), a de-novo missense mutation of HNF1β gene was detected. At 18 months of age our patient has persistent cholestasis and his itching is not under satisfactory control.

CONCLUSIONS

Alagille syndrome may not be the only syndrome determining paucity of interlobular bile ducts in neonates presenting with cholestasis and renal impairment, especially in small for gestational age newborns. We suggest that HNF1β deficiency should also be ruled out, taking into consideration HNF1β mutations, together with Alagille syndrome, in next generation sequencing strategies in neonates with cholestasis, renal impairment and/or paucity of interlobular bile ducts at liver biopsy.

17q12 Deletion Syndrome as a Rare Cause for Diabetes Mellitus Type MODY5

CONTEXT

Maturity-onset diabetes of the young type 5 (MODY5) is caused by mutations of the hepatocyte nuclear factor 1 homeobox β gene (HNF1B). Although clinical characteristics and therapeutic management of MODY5 are increasingly better defined, adequate consideration of the frequent association of MODY5 with 17q12 deletion syndrome is often missing.

EVIDENCE ACQUISITION

We report two cases of patients with 17q12 deletion syndrome who presented to our clinic. Furthermore, we reviewed the existing literature to improve systematic diagnostic and therapeutic approaches. A PubMed search using the terms 17q12 deletion syndrome, diabetes mellitus type MODY5, and/or HNF1B was performed.

EVIDENCE SYNTHESIS

Three hundred sixty-one cases of postnatal 17q12 deletion syndrome were assessed, and details on clinical manifestations, diagnostic approaches, and therapeutic management were reviewed and compared with the two cases at our clinic. Furthermore, data on pathogenic mechanisms and their clinical implications were evaluated.

CONCLUSION

The 17q12 deletion syndrome usually comprises MODY5, structural or functional abnormalities of the kidneys, and neurodevelopmental or neuropsychiatric disorders. A complete deletion of HNF1B can be found in about 50% of patients with MODY5. A wide variety of additional clinical features, including genital and brain malformations, has been reported. Because HNF1B deletions are virtually always part of a 17q12 deletion syndrome and common genetic analyses for evaluation of MODY5 are unable to detect the deletion of a 1.4-Mb chromosomal region, initial attention to the syndromal features at the stage of diagnosis is of considerable importance for establishing correct diagnosis, subsequent therapy, and interdisciplinary patient care.

Genome-wide methylomic analysis in individuals with HNF1B intragenic mutation and 17q12 microdeletion

Heterozygous mutation of the transcription factor HNF1B is the most common cause of monogenetic developmental renal disease. Disease-associated mutations fall into two categories: HNF1B intragenic mutations and a 1.3 Mb deletion at chromosome 17q12. An increase in neurodevelopmental disorders has been observed in individuals harbouring the 17q12 deletion but not in patients with HNF1B coding mutations.Previous investigations have concentrated on identifying a genetic cause for the increase in behavioural problems seen in 17q12 deletion carriers. We have taken the alternative approach of investigating the DNA methylation profile of these two HNF1B genotype groups along with controls matched for age, gender and diabetes status using the Illumina 450K DNA methylation array (total sample n = 60).We identified a number of differentially methylated probes (DMPs) that were associated with HNF1B-associated disease and passed our stringent experiment-wide significance threshold. These associations were largely driven by the deletion patients and the majority of the significant probes mapped to the 17q12 deletion locus. The observed changes in DNA methylation at this locus were not randomly dispersed and occurred in clusters, suggesting a regulatory mechanism reacting to haploinsufficiency across the entire deleted region.Along with these deletion-specific changes in DNA methylation, we also identified a shared DNA methylation signature in both mutation and deletion patient groups indicating that haploinsufficiency of HNF1B impacts on the methylome of a number of genes, giving further insight to the role of HNF1B.

Monogenic Diabetes in Children and Adolescents: Recognition and Treatment Options

PURPOSE OF REVIEW

We provide a review of monogenic diabetes in young children and adolescents with a focus on recognition, management, and pharmacological treatment.

RECENT FINDINGS

Monogenic forms of diabetes account for approximately 1-2% of diabetes in children and adolescents, and its incidence has increased in recent years due to greater awareness and wider availability of genetic testing. Monogenic diabetes is due to single gene defects that primarily affect beta cell function with more than 30 different genes reported. Children with antibody-negative, C-peptide-positive diabetes should be evaluated and genetically tested for monogenic diabetes. Accurate genetic diagnosis impacts treatment in the most common types of monogenic diabetes, including the use of sulfonylureas in place of insulin or other glucose-lowering agents or discontinuing pharmacologic treatment altogether. Diagnosis of monogenic diabetes can significantly improve patient care by enabling prediction of the disease course and guiding appropriate management and treatment.

Exocrine pancreatic dysfunction is common in hepatocyte nuclear factor 1β-associated renal disease and can be symptomatic

Background

Heterozygous mutations in the HNF1B gene are the most common monogenic cause of developmental kidney disease. Extrarenal phenotypes frequently occur, including diabetes mellitus and pancreatic hypoplasia; the latter is associated with subclinical exocrine dysfunction. We measured faecal elastase-1 in patients with HNF1B-associated disease regardless of diabetes status and assessed the degree of symptoms associated with pancreatic exocrine deficiency.

Methods

Faecal elastase-1 was measured in 29 patients with a known HNF1B mutation. We defined a low faecal elastase-1 concentration based on the 2.5 percentile of 99 healthy control individuals (410 μg/g stool). Symptoms related to pancreatic exocrine dysfunction were assessed and a subset of the HNF1B cohort (n  =  6) underwent pancreatic imaging.

Results

Faecal elastase-1 was below the 2.5 percentile of the control cohort in 18/29 (62%) patients with HNF1B-associated renal disease. A total of 8/29 (28%) had a measurement suggestive of exocrine pancreatic insufficiency at  <200 μg/g stool; of these, 3 suffered with abdominal pain, loose stools and/or unintentional weight loss. All three experienced symptomatic improvement and weight gain after commencing pancreatic enzyme replacement therapy. Faecal elastase-1 was low in 7/15 (47%) HNF1B patients without diabetes compared with 11/14 (79%) of those with diabetes (P  =  0.1).

Conclusions

Faecal elastase-1 deficiency is a common feature of HNF1B-associated renal disease even when diabetes is not present and pancreatic exocrine deficiency may be more symptomatic than previously suggested. Faecal elastase-1 should be measured in all patients with known HNF1B-associated disease complaining of chronic abdominal pain, loose stools or unintentional weight loss. The discovery of a low faecal elastase-1 concentration in individuals with developmental kidney disease of uncertain cause should prompt referral for HNF1B genetic testing.

Genetic basis of human congenital anomalies of the kidney and urinary tract

The clinical spectrum of congenital anomalies of the kidney and urinary tract (CAKUT) encompasses a common birth defect in humans that has significant impact on long-term patient survival. Overall, data indicate that approximately 20% of patients may have a genetic disorder that is usually not detected based on standard clinical evaluation, implicating many different mutational mechanisms and pathogenic pathways. In particular, 10% to 15% of CAKUT patients harbor an unsuspected genomic disorder that increases risk of neurocognitive impairment and whose early recognition can impact clinical care. The emergence of high-throughput genomic technologies is expected to provide insight into the common and rare genetic determinants of diseases and offer opportunities for early diagnosis with genetic testing.