Anomalies of the TCF2 gene are the main cause of fetal bilateral hyperechogenic kidneys

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.

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 of cystinuria with a heterozygous pathogenic variant in SLC7A9 gene associated with isolated hyperechogenic fetal kidneys: A case report

Cystinuria is suspected antenatally by a hyperechogenic fetal colonic content. We report the first prenatal case of autosomal dominant SLC7A9-related cystinuria associated with isolated hyperechogenic kidneys as the only prenatal sonographic sign.

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).

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.

Ultrasound Diagnosis of Malformations of the Fetal Kidneys and Urinary System

Malformations of the fetal kidneys and urinary system are common and easily visualized and diagnosed on ultrasound. This article presents the typical sonographic findings of these abnormalities during the various stages of pregnancy. Because malformations of the urogenital tract often have an association with genetic diseases/ciliopathies, these are also discussed. To complete the article, we provide a brief overview of the normal anatomy of the kidneys and urinary system. The normal anatomy and malformations of the genitalia will not be discussed in this article due to their complexity.

Development of a tool for predicting HNF1B mutations in children and young adults with congenital anomalies of the kidneys and urinary tract

BACKGROUND

We aimed to develop a tool for predicting HNF1B mutations in children with congenital abnormalities of the kidneys and urinary tract (CAKUT).

METHODS

The clinical and laboratory data from 234 children and young adults with known HNF1B mutation status were collected and analyzed retrospectively. All subjects were randomly divided into a training (70%) and a validation set (30%). A random forest model was constructed to predict HNF1B mutations. The recursive feature elimination algorithm was used for feature selection for the model, and receiver operating characteristic curve statistics was used to verify its predictive effect.

RESULTS

A total of 213 patients were analyzed, including HNF1B-positive (mut + , n = 109) and HNF1B-negative (mut - , n = 104) subjects. The majority of patients had mild chronic kidney disease. Kidney phenotype was similar between groups, but bilateral kidney anomalies were more frequent in the mut + group. Hypomagnesemia and hypermagnesuria were the most common abnormalities in mut + patients and were highly selective of HNF1B. Hypomagnesemia based on age-appropriate norms had a better discriminatory value than the age-independent cutoff of 0.7 mmol/l. Pancreatic anomalies were almost exclusively found in mut + patients. No subjects had hypokalemia; the mean serum potassium level was lower in the HNF1B cohort. The abovementioned, discriminative parameters were selected for the model, which showed a good performance (area under the curve: 0.85; sensitivity of 93.67%, specificity of 73.57%). A corresponding calculator was developed for use and validation.

CONCLUSIONS

This study developed a simple tool for predicting HNF1B mutations in children and young adults with CAKUT.

Ultrasound and magnetic resonance imaging features of fetal urogenital anomalies: A pictorial essay

This pictorial essay focuses on ultrasound (US) and magnetic resonance imaging (MRI) features of fetal urogenital anomalies. Fetal urogenital malformations account for 30%-50% of all anomalies discovered during pregnancy or at birth. They are usually detected by fetal ultrasound exams. However, when ultrasound data on their characteristics is insufficient, MRI is the best option for detecting other associated anomalies. The prognosis highly depends on their type and whether they are associated with other fetal abnormalities.

When should we offer antenatal sequencing for urinary tract malformations? A systematic review, cohort study and meta-analysis

OBJECTIVE

Determine the incremental yield of prenatal exome sequencing (PES) over chromosome microarray (CMA) and/or karyotype for urinary tract malformations (UTMs).

METHOD

A prospective cohort study encompassing data from the English Genomic Medicine Service North Thames Laboratory Hub for fetuses with bilateral echogenic kidneys (BEKs) was combined with data from a systematic review. MEDLINE, EMBASE, Web of Science, MedRxiv and GreyLit were searched from 01/2010-02/2023 for studies reporting on the yield of PES over CMA or karyotype in fetuses with UTMs. Pooled incremental yield was determined using a random effects model. PROSPERO CRD42023364544.

RESULTS

Fourteen studies (410 cases) were included. The incremental yield for multisystem UTMs, any isolated UTMs, and BEKs was 31% [95% CI, 18%-46%; I2  = 78%], 16% [95% CI, 6%-26%; I2  = 80%] and 51% [95% CI, 27%-75%; I2  = 34%]. The most common clinical diseases and syndromes identified, based on the variant genes detected, were Bardet-Biedl syndrome (BBS genes), dominant and recessive polycystic kidney diseases (PKD1, PKD2 and PKHD1) and renal cysts and diabetes syndrome (HNF1B).

CONCLUSION

There was a notable incremental genetic diagnostic yield when PES was applied to multisystem UTMs and BEKs. There was a modest incremental yield when this technique was used for UTMs other than BEKs.

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.

Characterization of the prenatal renal phenotype associated with 17q12, HNF1B, microdeletions

OBJECTIVE

Recurrent deletions involving 17q12 are associated with a variety of clinical phenotypes, including congenital abnormalities of the kidney and urinary tract (CAKUT), maturity onset diabetes of the young, type 5, and neurodevelopmental disorders. Structural and/or functional renal disease is the most common phenotypic feature, although the prenatal renal phenotypes and the postnatal correlates have not been well characterized.

METHOD

We reviewed pre- and postnatal medical records of 26 cases with prenatally or postnatally identified 17q12/HNF1B microdeletions (by chromosomal microarray or targeted gene sequencing), obtained through a multicenter collaboration. We specifically evaluated 17 of these cases (65%) with reported prenatal renal ultrasound findings.

RESULTS

Heterogeneous prenatal renal phenotypes were noted, most commonly renal cysts (41%, n = 7/17) and echogenic kidneys (41%), although nonspecific dysplasia, enlarged kidneys, hydronephrosis, pelvic kidney with hydroureter, and lower urinary tract obstruction were also reported. Postnatally, most individuals developed renal cysts (73%, 11/15 live births), and there were no cases of end-stage renal disease during childhood or the follow-up period.

CONCLUSION

Our findings demonstrate that copy number variant analysis to assess for 17q12 microdeletion should be considered for a variety of prenatally detected renal anomalies. It is important to distinguish 17q12 microdeletion from other etiologies of CAKUT as the prognosis for renal function and presence of associated findings are distinct and may influence pregnancy and postnatal management.

Fetal hyperechoic kidney cohort study and a meta-analysis

Objective: To investigate the positive rate of chromosomal and monogenic etiologies and pregnancy outcomes in fetuses with hyperechoic kidney, and to provide more information for genetic counseling and prognosis evaluation. Methods: We performed a retrospective analysis of 25 cases of hyperechoic kidney diagnosed prenatal in the Second Affiliated Hospital of Harbin Medical University and Harbin Red Cross Central Hospital (January 2017-December 2022). Furthermore, we conducted a meta-analysis of a series of hyperechoic kidneys (HEK) in the literature to assess the incidence of chromosomal and monogenic etiologies, mortality, and pooled odds ratio (OR) estimates of the association between the incidence of these outcomes and other associated ultrasound abnormalities. Results: 25 fetuses of HEK were enrolled in the cohort study, including 14 with isolated hyperechoic kidney (IHK) and 11 with non-isolated hyperechoic kidney (NIHK). Chromosomal aneuploidies were detected in 4 of 20 patients (20%). The detection rate of pathogenic or suspected pathogenic copy number variations (CNVs) was 29% (4/14) for IHK and 37% (4/11) for NIHK. Whole exome sequencing (WES) was performed in 5 fetuses, and pathogenic genes were detected in all of them. The rate of termination of pregnancy was 56% in HEK. 21 studies including 1,178 fetuses were included in the meta-analysis. No case of abnormal chromosome karyotype or (intrauterine death)IUD was reported in fetuses with IHK. In contrast, the positive rate of karyotype in NIHK was 22% and that in HEK was 20%, with the ORs of 0.28 (95% CI 0.16-0.51) and 0.25, (95% CI 0.14-0.44), respectively. The positive rate of (chromosome microarray analysis) CMA in IHK was 59% and that in NIHK was 32%, with the ORs of 1.46 (95% CI 1.33-1.62) and 0.48 (95% CI, 0.28-0.85), respectively. The positive rate of monogenic etiologies in IHK was 31%, with the OR of 0.80 (95% CI 0.25-2.63). In IHK, the termination rate was 21% and neonatal mortality was 13%, with the ORs of 0.26 (95% CI, 0.17-0.40), 1.72 (95% CI, 1.59-1.86), and that in NIHK was 63%, 0.15 (95% CI, 0.10-0.24); 11%, 0.12 (95% CI, 0.06-0.26), respectively. The intrauterine mortality in NIHK group was 2%, with the OR of 0.02 (95% CI, 0.01-0.05). HNF1B variant has the highest incidence (26%) in IHK. Conclusion: The positive rate of karyotype was 20% in HEK and 22% in NIHK. The positive rate of CMA was 32% in NIHK and 59% in IHK. The positive rate of IHK monogenic etiologies was 31%. HNF1B gene variation is the most common cause of IHK. The overall fetal mortality rate of NIHK is significantly higher than that of IHK. The amount of amniotic fluid, kidney size and the degree of corticomedullary differentiation have a great impact on the prognosis, these indicators should be taken into consideration to guide clinical consultation and decision-making.

Kidney Organoid Derived from Human Pluripotent and Adult Stem Cells for Disease Modeling

Kidney disease affects a significant portion of the global population, yet effective therapies are lacking despite advancements in identifying genetic causes. This limitation can be attributed to the absence of adequate in vitro models that accurately mimic human kidney disease, hindering targeted therapeutic development. However, the emergence of human induced pluripotent stem cells (PSCs) and the development of organoids using them have opened up a way to model kidney development and disease in humans, as well as validate the effects of new drugs. To fully leverage their capabilities in these fields, it is crucial for kidney organoids to closely resemble the structure and functionality of adult human kidneys. In this review, we aim to discuss the potential of using human PSCs or adult kidney stem cell-derived kidney organoids to model genetic kidney disease and renal cancer.

Classifying and evaluating fetuses with multicystic dysplastic kidney in etiologic studies

Multicystic dysplastic kidney (MCDK) is one of the most common fetal malformations, but its etiology remains unclear. Identification of the molecular etiology could provide a basis for prenatal diagnosis, consultation, and prognosis evaluation for MCDK fetuses. We used chromosome microarray analysis (CMA) and whole-exome sequencing (WES) to conduct genetic tests on MCDK fetuses and explore their genetic etiology. A total of 108 MCDK fetuses with or without other extrarenal abnormalities were selected. Karyotype analysis of 108 MCDK fetuses showed an abnormal karyotype in 4 (3.7%, 4/108) of the fetuses. However, CMA detected 15 abnormal copy number variations (CNVs) (14 pathogenic CNVs, and one variant of unknown significance [VUS] CNVs), in addition to four cases that were consistent with the results of karyotype analysis. Out of the 14 pathogenic CNVs cases, three were of 17q12 microdeletion, two of 22q11.21 microdeletion, 22q11.21 microduplication uniparental disomy (UPD), and one case of 4q31.3q32.2 microdeletion, 7q11.23 microduplication, 15q11.2 microdeletion, 16p11.2 microdeletion, and 17p12 microdeletion. Of the 89 MCDK fetuses with normal karyotype analysis and CMA, 15 were tested by WES. Two (13.3%, 2/15) fetuses were identified by WES as Bardet-Biedl syndrome (BBS) 1 and BBS2. Combined application of CMA-WES to detect MCDK fetuses can significantly improve the detection rate of genetic etiology, providing a basis for consultation, and prognosis evaluation.

[Developmental abnormalities of the kidney]

Les anomalies du développement rénal sont fréquentes chez le fœtus et correspondent à un défaut des étapes de la néphrogenèse. La plupart d’entre elles ont une évolution favorable, mais la gravité potentielle de certaines malformations rend leur dépistage et leur prise en charge précoce essentiels. Le dépistage de ces anomalies repose sur l’échographie fœtale. L’échographie devra préciser le pronostic de l’anomalie en recherchant des critères de gravité, tels qu’une atteinte rénale bilatérale, une altération de la quantité de liquide amniotique, témoin d’une altération de la fonction rénale fœtale, ou encore l’existence d’atteintes extra-rénales associées. Dans les cas les plus sévères, une prise en charge dans un centre pluridisciplinaire de diagnostic prénatal (CPDPN) est indispensable. Les anomalies du développement rénal peuvent être isolées ou s’inscrire dans le cadre d’un syndrome poly-malformatif. L’apport de la génétique dans la compréhension de ces anomalies est d’une aide considérable.

HNF1B Alters an Evolutionarily Conserved Nephrogenic Program of Target Genes

SIGNIFICANCE STATEMENT

Mutations in hepatocyte nuclear factor-1 β ( HNF1B ) are the most common monogenic causes of congenital renal malformations. HNF1B is necessary to directly reprogram fibroblasts to induced renal tubule epithelial cells (iRECs) and, as we demonstrate, can induce ectopic pronephric tissue in Xenopus ectodermal organoids. Using these two systems, we analyzed the effect of HNF1B mutations found in patients with cystic dysplastic kidney disease. We found cross-species conserved targets of HNF1B, identified transcripts that are differentially regulated by the patient-specific mutant protein, and functionally validated novel HNF1B targets in vivo . These results highlight evolutionarily conserved transcriptional mechanisms and provide insights into the genetic circuitry of nephrogenesis.

BACKGROUND

Hepatocyte nuclear factor-1 β (HNF1B) is an essential transcription factor during embryogenesis. Mutations in HNF1B are the most common monogenic causes of congenital cystic dysplastic renal malformations. The direct functional consequences of mutations in HNF1B on its transcriptional activity are unknown.

METHODS

Direct reprogramming of mouse fibroblasts to induced renal tubular epithelial cells was conducted both with wild-type HNF1B and with patient mutations. HNF1B was expressed in Xenopus ectodermal explants. Transcriptomic analysis by bulk RNA-Seq identified conserved targets with differentially regulated expression by the wild-type or R295C mutant. CRISPR/Cas9 genome editing in Xenopus embryos evaluated transcriptional targets in vivo .

RESULTS

HNF1B is essential for reprogramming mouse fibroblasts to induced renal tubular epithelial cells and induces development of ectopic renal organoids from pluripotent Xenopus cells. The mutation R295C retains reprogramming and inductive capacity but alters the expression of specific sets of downstream target genes instead of diminishing overall transcriptional activity of HNF1B. Surprisingly, targets associated with polycystic kidney disease were less affected than genes affected in congenital renal anomalies. Cross-species-conserved transcriptional targets were dysregulated in hnf1b CRISPR-depleted Xenopus embryos, confirming their dependence on hnf1b .

CONCLUSIONS

HNF1B activates an evolutionarily conserved program of target genes that disease-causing mutations selectively disrupt. These findings provide insights into the renal transcriptional network that controls nephrogenesis.

Maturity-onset diabetes of the young secondary to HNF1B variants (HNF1B-MODY): a series of 10 patients from a single diabetes center

BACKGROUND

Maturity-Onset Diabetes of the Young (MODY) is an autosomal dominant condition and represents 1-5% of all cases of diabetes mellitus. MODY is often misdiagnosed as type 1 or type 2 diabetes. The rare subtype 5 (HNF1B-MODY) is due to hepatocyte nuclear factor 1β (HNF1B) molecular alteration and is remarkable for its multisystemic phenotypes characterized by a broad spectrum of pancreatic and extra-pancreatic clinical manifestations.

METHODS

Retrospective study of patients with HNF1B-MODY diagnosis followed in the Centro Hospitalar Universitário Lisboa Central (Lisbon, Portugal). Demographic data, medical history, clinical and laboratory data, follow-up and treatment procedures were obtained from electronic medical records.

RESULTS

We found 10 patients with HNF1B variants (7 index cases). The median age at diabetes diagnosis was 28 (IQR 24) years and the median age at HNF1B-MODY diagnosis was 40.5 (IQR 23) years. Six patients were initially misclassified as type 1 and 4 as type 2 diabetes. The average time between diabetes diagnosis and the diagnosis of HNF1B-MODY was 16.5 years. Diabetes was the first manifestation in half of the cases. The other half presented with kidney malformations and chronic kidney disease at pediatric age as the first manifestation. All these patients were submitted to kidney transplantation. Long-term diabetes complications included retinopathy (4/10), peripheral neuropathy (2/10) and ischemic cardiomyopathy (1/10). Other extra-pancreatic manifestations included liver test alterations (4/10) and congenital malformation of the female reproductive tract (1/6). History of a first-degree relative with diabetes and/or nephropathy diagnosed at a young age was present in 5 of the 7 index cases.

CONCLUSIONS

Despite being a rare disease, HNF1B-MODY is underdiagnosed and often misclassified. It should be suspected in patients with diabetes and CKD, especially when diabetes appears at a young age, a family history is present, and nephropathy appears before/shortly after the diagnosis of diabetes. Presence of unexplained liver disease increases the degree of suspicion for HNF1B-MODY. Early diagnosis is important to minimize complications and to allow familial screening and pre-conception genetic counseling. Trial registration not applicable due to the retrospective nature of the study, non-interventional.

Antenatally Diagnosed Kidney Anomalies

Congenital anomalies of the kidney and urinary tract encompass a broad spectrum of developmental conditions that together account for the majority of childhood chronic kidney diseases. Kidney abnormalities are the most commonly diagnosed congenital anomaly in children, and detection of this anomaly is increasing as a result of improved antenatal care and widespread access to more sensitive screening ultrasonography. Most paediatricians will encounter children with congenital kidney anomalies across a wide spectrum of disorders, and a broad understanding of the classification, investigation, and basis of management is important to appropriately direct their care.

What can we learn from kidney organoids?

The ability to generate 3-dimensional models of the developing human kidney via the directed differentiation of pluripotent stem cells-termed kidney organoids-has been hailed as a major advance in experimental nephrology. Although these provide an opportunity to interrogate human development, model-specific kidney diseases facilitate drug screening and even deliver bioengineered tissue; most of these prophetic end points remain to be realized. Indeed, at present we are still finding out what we can learn and what we cannot learn from this approach. In this review, we will summarize the approaches available to generate models of the human kidney from stem cells, the existing successful applications of kidney organoids, their limitations, and remaining challenges.

Consensus document on autosomal dominant polycystic kindey disease from the Spanish Working Group on Inherited Kindey Diseases. Review 2020

Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent cause of genetic renal disease and accounts for 6-10% of patients on kidney replacement therapy (KRT). Very few prospective, randomized trials or clinical studies address the diagnosis and management of this relatively frequent disorder. No clinical guidelines are available to date. This is a revised consensus statement from the previous 2014 version, presenting the recommendations of the Spanish Working Group on Inherited Kidney Diseases, which were agreed to following a literature search and discussions. Levels of evidence mostly are C and D according to the Centre for Evidence-Based Medicine (University of Oxford). The recommendations relate to, among other topics, the use of imaging and genetic diagnosis, management of hypertension, pain, cyst infections and bleeding, extra-renal involvement including polycystic liver disease and cranial aneurysms, management of chronic kidney disease (CKD) and KRT and management of children with ADPKD. Recommendations on specific ADPKD therapies are provided as well as the recommendation to assess rapid progression.

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.

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.

Maturity-Onset Diabetes of Young Type 5: Diabetes with Extrapancreatic Features

Objective

This case involves a new-onset diabetes patient diagnosed during pregnancy with the congenital dysplastic right kidney. Case Report. Clinical presentation, biochemical features, imaging in a patient with diabetes diagnosed during pregnancy, and congenital dysplastic right kidney. Discussion. We present a case of a 22-year-old female with the congenital dysplastic right kidney diagnosed with gestational diabetes mellitus after failing a 1-hour oral glucose tolerance test, requiring insulin during pregnancy. Because of the family history of diabetes and morphologic renal abnormalities at young ages on the maternal side of the family, our patient was evaluated for maturity-onset diabetes of adult and was found to have HNF-1β mutation.

Conclusion

This case highlights the importance of considering the diagnosis of maturity-onset diabetes of young and particularly MODY-5 in individuals with extrapancreatic features. MODY-5 should also be considered in a patient undergoing renal transplant at young ages with a family history of morphologic renal abnormalities.

A case report with functional characterization of a HNF1B mutation (p.Leu168Pro) causing MODY5

We previously performed next-generation sequencing-based genetic screening in patients with autoantibody-negative type 1 diabetes, and identified the p.Leu168Pro mutation in HNF1B. Here,we report the clinical course of the patient and the results of functional characterization of this mutation. The proband had bilateral renal hypodysplasia and developed insulin-dependent diabetes during childhood. The pathogenicity of Leu168Pro-HNF1B was evaluated with three-dimensional structure modeling, Western blotting, immunofluorescence analysis and luciferase reporter assays using human embryonic kidney 293 cells. Three-dimensional structure modeling predicted that the Leu168 residue is buried in the DNA-binding Pit-Oct-Unc-specific (POU_S) domain and forms a hydrophobic core. Western blotting showed that the protein expression level of Leu168Pro-HNF1B was lower than that of wild-type (WT) HNF1B. Immunofluorescence staining showed that both WT- and Leu168Pro-HNF1B were normally localized in the nucleus. The cells transfected with WT-HNF1B exhibited 5-fold higher luciferase reporter activity than cells transfected with an empty vector. The luciferase activities were comparable between WT-HNF1B/Leu168Pro-HNF1B and WT-HNF1B/empty vector co-transfection. In conclusion, Leu168Pro is a protein-destabilizing HNF1B mutation, and the destabilization is likely due to the structural changes involving the hydrophobic core of POU_S. The disease-causing Leu168Pro HNF1B mutation is a loss-of-function mutation without a dominant-negative effect.

Hepatocyte nuclear factor 1B mutation in a Chinese family with renal cysts and diabetes syndrome: A case report

BACKGROUND

Renal cysts and diabetes (RCAD) syndrome is an autosomal dominant diabetic renal disease. Precise molecular diagnosis of RCAD syndrome has proven valuable for understanding its mechanism and personalized therapy.

CASE SUMMARY

A RCAD patient and her family were studied to investigate potential responsible genes by the whole exome sequencing (WES). Candidate pathogenic variants were validated by Sanger sequencing. The clinical characteristics of RCAD patient were collected from medical records. Unlike those typical RCAD patients, we observed renal manifestation and prediabetes phenotype, but not reproductive organ phenotype and hypomagnesaemia. A novel 7-bp deletion mutation in exon 4 of the hepatocyte nuclear factor 1B, NM_000458: c.882_888del (p.V294fs), was identified by WES and confirmed by Sanger sequencing.

CONCLUSION

This novel mutation identified in a Chinese family with RCAD syndrome might be the molecular pathogenic basis of this disorder.

Reverse Phenotyping Maternal Cystic Kidney Disease by Diagnosis in a Newborn: Case Report and Literature Review on Neonatal Cystic Kidney Diseases

Summary. Kidney cysts are the most common kidney lesion, while congenital kidney cysts are mostly found in pediatric population. Neonatal kidney cysts can develop due to fetal malformations, rare genetic disorders or can be acquired which is very rare. Kidney cysts may be the only isolated finding or be part of the overall phenotype. They can be asymptomatic, found by ultrasound accidentally or can manifest from mild to life-threatening symptoms. Therefore, early diagnosis is very important. Autosomal dominant polycystic kidney disease and autosomal recessive polycystic kidney disease are the most common causes of kidney cysts in the neonatal population. This review highlights the most common kidney cystic diseases during the neonatal period and a rare clinical case of HNF1B-associated disease.

Hyperuricemia Is an Early and Relatively Common Feature in Children with HNF1B Nephropathy but Its Utility as a Predictor of the Disease Is Limited

Background: Hyperuricemia is recognized as an important feature of nephropathy, associated with a mutation in the hepatocyte nuclear factor-1B (HNF1B) gene, and could serve as a useful marker of the disease. However, neither a causal relationship nor its predictive value have been proven. The purpose of this study was to assess this in children with renal malformations, both with (mut+) and without HNF1B mutations (mut-). Methods: We performed a retrospective analysis of clinical characteristics of pediatric patients tested for HNF1B mutations, collected in a national registry. Results: 108 children were included in the study, comprising 43 mut+ patients and 65 mut- subjects. Mean sUA was higher and hyperuricemia more prevalent (42.5% vs. 15.4%) in HNF1B carriers. The two groups were similar with respect to respect to age, sex, anthropometric parameters, hypertension, and renal function. Renal function, fractional excretion of uric acid and parathyroid hormone level were independent predictors of sUA. The potential of hyperuricemia to predict mutation was low, and addition of hyperuricemia to a multivariate logistic regression model did not increase its accuracy. Conclusions: Hyperuricemia is an early and common feature of HNF1B nephropathy. A strong association of sUA with renal function and parathyroid hormone limits its utility as a reliable marker to predict HNF1B mutation among patients with kidney anomalies.

Molecular Pathophysiology of Autosomal Recessive Polycystic Kidney Disease

Autosomal recessive polycystic kidney disease (ARPKD) is a rare disorder and one of the most severe forms of polycystic kidney disease, leading to end-stage renal disease (ESRD) in childhood. PKHD1 is the gene that is responsible for the vast majority of ARPKD. However, some cases have been related to a new gene that was recently identified (DZIP1L gene), as well as several ciliary genes that can mimic a ARPKD-like phenotypic spectrum. In addition, a number of molecular pathways involved in the ARPKD pathogenesis and progression were elucidated using cellular and animal models. However, the function of the ARPKD proteins and the molecular mechanism of the disease currently remain incompletely understood. Here, we review the clinics, treatment, genetics, and molecular basis of ARPKD, highlighting the most recent findings in the field.

Mapping of the amniotic fluid proteome of fetuses with congenital anomalies of the kidney and urinary tract identifies plastin 3 as a protein involved in glomerular integrity

Congenital anomalies of the kidney and the urinary tract (CAKUT) are the first cause of chronic kidney disease in childhood. Several genetic and environmental origins are associated with CAKUT, but most pathogenic pathways remain elusive. Considering the amniotic fluid (AF) composition as a proxy for fetal kidney development, we analyzed the AF proteome from non-severe CAKUT (n = 19), severe CAKUT (n = 14), and healthy control (n = 22) fetuses using LC-MS/MS. We identified 471 significant proteins that discriminated the three AF groups with 81% precision. Among them, eight proteins independent of gestational age (CSPG4, LMAN2, ENDOD1, ANGPTL2, PRSS8, NGFR, ROBO4, PLS3) were associated with both the presence and the severity of CAKUT. Among those, five were part of a protein-protein interaction network involving proteins previously identified as being potentially associated with CAKUT. The actin-bundling protein PLS3 (plastin 3) was the only protein displaying a gradually increased AF abundance from control, via non-severe, to severe CAKUT. Immunohistochemistry experiments showed that PLS3 was expressed in the human fetal as well as in both the fetal and the postnatal mouse kidney. In zebrafish embryos, depletion of PLS3 led to a general disruption of embryonic growth including reduced pronephros development. In postnatal Pls3-knockout mice, kidneys were macroscopically normal, but the glomerular ultrastructure showed thickening of the basement membrane and fusion of podocyte foot processes. These structural changes were associated with albuminuria and decreased expression of podocyte markers including Wilms' tumor-1 protein, nephrin, and podocalyxin. In conclusion, we provide the first map of the CAKUT AF proteome that will serve as a reference for future studies. Among the proteins strongly associated with CAKUT, PLS3 did surprisingly not specifically affect nephrogenesis but was found as a new contributor in the maintenance of normal kidney function, at least in part through the control of glomerular integrity. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

A case of 17q12 deletion syndrome that presented antenatally with markedly enlarged kidneys and clinically mimicked autosomal recessive polycystic kidney disease

The gene encoding hepatocyte nuclear factor 1β (HNF1B), a transcription factor involved in the development of the kidney and other organs, is located on chromosome 17q12. Heterozygous deletions of chromosome 17q12, which involve 15 genes including HNF1B, are known as 17q12 deletion syndrome and are a common cause of congenital anomalies of the kidneys and urinary tract (CAKUT) and may also present as a multisystem disorder. Autosomal recessive polycystic kidney disease (ARPKD), on the other hand, is a severe form of polycystic kidney disease caused by mutations in PKHD1 (polycystic kidney and hepatic disease 1). It is important to differentiate between these two diseases because they differ significantly in inheritance patterns, renal prognosis, and extrarenal manifestations. Here we report a case of 17q12 deletion syndrome that clinically mimicked ARPKD in which genetic testing was essential for appropriate genetic counseling and monitoring of possible extrarenal manifestations. The patient presented antenatally with markedly enlarged kidneys and showed bilaterally hyperechoic kidneys with poor corticomedullary differentiation and multiple cysts on ultrasonography. There was no family history of renal disease. ARPKD was clinically suspected and genetic testing was performed to confirm diagnosis, resulting in an unexpected finding of 17q12 deletion including HNF1B. While some research has been done to identify patients that should be tested for HNF1B anomalies, this case illustrates the difficulty of recognizing HNF1B-related disease and the importance of genetic testing in appropriately managing CAKUT cases.

Insights into the etiology and physiopathology of MODY5/HNF1B pancreatic phenotype with a mouse model of the human disease

Maturity-onset diabetes of the young type 5 (MODY5) is due to heterozygous mutations or deletion of HNF1B. No mouse models are currently available to recapitulate the human MODY5 disease. Here, we investigate the pancreatic phenotype of a unique MODY5 mouse model generated by heterozygous insertion of a human HNF1B splicing mutation at the intron-2 splice donor site in the mouse genome. This Hnf1bsp2/+ model generated with targeted mutation of Hnf1b mimicking the c.544+1G>T (T) mutation identified in humans, results in alternative transcripts and a 38% decrease of native Hnf1b transcript levels. As a clinical feature of MODY5 patients, the hypomorphic mouse model Hnf1bsp2/+ displays glucose intolerance. Whereas Hnf1bsp2/+ isolated islets showed no altered insulin secretion, we found a 65% decrease in pancreatic insulin content associated with a 30% decrease in total large islet volume and a 20% decrease in total β-cell volume. These defects were associated with a 30% decrease in expression of the pro-endocrine gene Neurog3 that we previously identified as a direct target of Hnf1b, showing a developmental etiology. As another clinical feature of MODY5 patients, the Hnf1bsp2/+ pancreases display exocrine dysfunction with hypoplasia. We observed chronic pancreatitis with loss of acinar cells, acinar-to-ductal metaplasia, and lipomatosis, with upregulation of signaling pathways and impaired acinar cell regeneration. This was associated with ductal cell deficiency characterized by shortened primary cilia. Importantly, the Hnf1bsp2/+ mouse model reproduces the pancreatic features of the human MODY5/HNF1B disease, providing a unique in vivo tool for molecular studies of the endocrine and exocrine defects and to advance basic and translational research. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Etiologies and outcomes of prenatally diagnosed hyperechogenic kidneys

OBJECTIVES

To determine etiologies and outcomes of fetal hyperechogenic kidneys (HEK).

METHODS

We conducted a retrospective chart review of HEK in British Columbia (January 2013-December 2019) and literature review.

RESULTS

We identified 20 cases of HEK without other anomalies (isolated) in our provincial cohort, one was lost to follow-up. Eight had testable genetic etiologies (autosomal dominant polycystic kidney disease [ADPKD], autosomal recessive polycystic kidney disease [ARPKD], Bardet-Biedl syndrome [BBS], and HNF1B-related disorder). The remaining seven did not have an identifiable genetic etiology. Of cases without a genetic etiology with postnatal follow-up (n = 6) there were no abnormalities of blood pressure, creatinine/estimated glomerular filtration rate or urinalysis identified with follow-up from 2-71 months. We report 11 cases with extrarenal anomalies (nonisolated), with outcomes and etiologies. We identified 224 reported cases of isolated HEK in the literature. A potentially testable genetic etiology was found in 128/224 (57.1%). The neonatal death rate in those with testable etiologies was 17/128 (13.3%) compared to 2/96 (2.1%) when testable etiologies were excluded.

CONCLUSIONS

Genetic etiologies (ARPKD, ADPKD, BBS, HNF1B-related disorder, Beckwith-Wiedemann syndrome, tubular dysgenesis, familial nephroblastoma, and cytogenetic abnormalities) account for approximately half of prenatally isolated HEK; once excluded there are few neonatal deaths and short-term renal outcomes may be normal. There remains a paucity of knowledge about long-term renal outcomes.

Variable Expressivity of HNF1B Nephropathy, From Renal Cysts and Diabetes to Medullary Sponge Kidney Through Tubulo-interstitial Kidney Disease

Introduction

In humans, heterozygous mutations of hepatocyte nuclear factor 1beta (HNF1B) are responsible for a dominant inherited disease with both renal and extrarenal phenotypes. HNF1B nephropathy is the umbrella term that includes the various kidney phenotypes of the disease, ranging from congenital anomalies of the kidney and urinary tract (CAKUT), to tubular transport abnormalities, to chronic tubulointerstitial and cystic renal disease.

Methods

We describe 7 families containing 13 patients with ascertained HNF1B nephropathy. All patients underwent genetic testing and clinical, laboratory, and instrumental assessment, including renal imaging and evaluation of extrarenal HNF1B manifestations.

Results

Significant inter- and intrafamilial variability of HNF1B nephropathy has been observed. In our cohort, HNF1B pathogenic variants presented with renal cysts and diabetes syndrome (RCAD); renal cystic phenotype mimicking autosomal dominant polycystic kidney disease (ADPKD); autosomal dominant tubulointerstitial kidney disease (ADTKD) with or without hyperuricemia and gout; CAKUT; and nephrogenic diabetes insipidus (NDI). Of note, for the first time, we describe the occurrence of medullary sponge kidney (MSK) in a family harboring the HNF1B whole-gene deletion at chromosome 17q12. Genotype characterization led to the identification of an additional 6 novel HNF1B pathogenic variants, 3 frameshift, 2 missense, and 1 nonsense.

Conclusion

HNF1B nephropathy may present with a highly variable renal phenotype in adult patients. We expand the HNF1B renal clinical picture to include MSK as a potential new finding. Finally, we expand the allelic repertoire of the disease by adding novel HNF1B pathogenic variants.

Developmental Renal Glomerular Defects at the Origin of Glomerulocystic Disease

The architecture of renal glomeruli is acquired through intricate and still poorly understood developmental steps. In our study we identify a crucial glomerular morphogenetic event in nephrogenesis that drives the remodeling/separation of the prospective vascular pole (the future entrance of the glomerular arterioles) and the urinary pole (the tubular outflow). We demonstrate that this remodeling is genetically programmed. In fact, in mouse and human, the absence of HNF1B impairs the remodeling/separation of the two poles, leading to trapping and constriction of the tubular outflow inside the glomerulus. This aberration gives rise to obstructive glomerular dilations upon the initiation of primary urine production. In this context, we show that pharmacological decrease of glomerular filtration significantly contains cystic expansion. From a developmental point of view, our study discloses a crucial event on glomerular patterning affecting the "inside-outside" fate of the epithelia in the renal glomerulus.

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.

Maturity-onset diabetes of the young type 5 a MULTISYSTEMIC disease: a CASE report of a novel mutation in the HNF1B gene and literature review

BACKGROUND

Diabetes mellitus with autosomal dominant inheritance, such as maturity-onset diabetes of the young (MODY), is a genetic form of diabetes mellitus. MODY is a type of monogenic diabetes mellitus in which multiple genetic variants may cause an alteration to the functioning of beta cells. The three most known forms of MODY are caused by modifications to the hnf4a, gck, and hnf1a genes. However, other MODY variants can cause multiple alterations in the embryonic development of the endoderm. This is the case in patients presenting with MODY5, who have a mutation of the hepatic nuclear factor 1B (hnf1b) gene.

CASE PRESENTATION

We present the clinical case of a 15 year-old patient with a family history of diabetes mellitus and a classical MODY type 5 (MODY5) phenotype involving the pancreas and kidney, with a novel, unreported mutation in the hnf1b gene.

CONCLUSIONS

MODY5 is characterised by a mutation in the hnf1b gene, which plays an important role in the development and function of multiple organs. It should be suspected in patients with unusual diabetes and multisystem involvement unrelated to diabetes.

GRAPHICAL ABSTRACT

Bardet-Biedl syndrome: Antenatal presentation of forty-five fetuses with biallelic pathogenic variants in known Bardet-Biedl syndrome genes

Bardet-Biedl syndrome (BBS) is an emblematic ciliopathy associated with retinal dystrophy, obesity, postaxial polydactyly, learning disabilities, hypogonadism and renal dysfunction. Before birth, enlarged/cystic kidneys as well as polydactyly are the hallmark signs of BBS to consider in absence of familial history. However, these findings are not specific to BBS, raising the problem of differential diagnoses and prognosis. Molecular diagnosis during pregnancies remains a timely challenge for this heterogeneous disease (22 known genes). We report here the largest cohort of BBS fetuses to better characterize the antenatal presentation. Prenatal ultrasound (US) and/or autopsy data from 74 fetuses with putative BBS diagnosis were collected out of which molecular diagnosis was established in 51 cases, mainly in BBS genes (45 cases) following the classical gene distribution, but also in other ciliopathy genes (6 cases). Based on this, an updated diagnostic decision tree is proposed. No genotype/phenotype correlation could be established but postaxial polydactyly (82%) and renal cysts (78%) were the most prevalent symptoms. However, autopsy revealed polydactyly that was missed by prenatal US in 55% of the cases. Polydactyly must be carefully looked for in pregnancies with apparently isolated renal anomalies in fetuses.

Amniotic fluid peptides predict postnatal kidney survival in developmental kidney disease

Although a rare disease, bilateral congenital anomalies of the kidney and urinary tract (CAKUT) are the leading cause of end stage kidney disease in children. Ultrasound-based prenatal prediction of postnatal kidney survival in CAKUT pregnancies is far from accurate. To improve prediction, we conducted a prospective multicenter peptidome analysis of amniotic fluid spanning 140 evaluable fetuses with CAKUT. We identified a signature of 98 endogenous amniotic fluid peptides, mainly composed of fragments from extracellular matrix proteins and from the actin binding protein thymosin-β4. The peptide signature predicted postnatal kidney outcome with an area under the curve of 0.96 in the holdout validation set of patients with CAKUT with definite endpoint data. Additionally, this peptide signature was validated in a geographically independent sub-cohort of 12 patients (area under the curve 1.00) and displayed high specificity in non-CAKUT pregnancies (82 and 94% in 22 healthy fetuses and in 47 fetuses with congenital cytomegalovirus infection respectively). Change in amniotic fluid thymosin-β4 abundance was confirmed with ELISA. Knockout of thymosin-β4 in zebrafish altered proximal and distal tubule pronephros growth suggesting a possible role of thymosin β4 in fetal kidney development. Thus, recognition of the 98-peptide signature in amniotic fluid during diagnostic workup of prenatally detected fetuses with CAKUT can provide a long-sought evidence base for accurate management of the CAKUT disorder that is currently unavailable.

Genotype and Phenotype Analyses in Pediatric Patients with HNF1B Mutations

HNF1B mutations, one of the most common causes of congenital anomalies of the kidney and urinary tract, manifest as various renal and extrarenal phenotypes. We analyzed the genotype-phenotype correlations in 14 pediatric patients with HNF1B mutations. Genetic studies revealed total gene deletion in six patients (43%). All patients had bilateral renal abnormalities, primarily multiple renal cysts. Twelve patients exhibited progressive renal functional deterioration, and six of them progressed to kidney failure. The annual reduction in estimated glomerular filtration rate was−2.1 mL/min/1.73 m². Diabetes developed in five patients (36%), including one patient with new-onset diabetes after transplantation. Neurological deficits were noted in three patients (21%), one with total gene deletion and two with missense mutations. Pancreatic abnormalities were more frequent in patients with missense mutations than in patients with other types of mutations. Genotype showed no significant correlation with renal outcomes or other extrarenal manifestations. The HNF1B scores at the times of onset and genetic diagnosis were <8 in two patients and one patient, respectively. Diagnosis of HNF1B mutations is clinically difficult because of extreme phenotypic variability and incomplete penetrance. Furthermore, some phenotypes develop with age. Therefore, patient age should be taken into consideration to increase the diagnostic rate, because some phenotypes develop with age.

[Kidney Cysts and Cystic Nephropathies in Children - A Consensus Guideline by 10 German Medical Societies]

This consensus-based guideline was developed by all relevant German pediatric medical societies. Ultrasound is the standard imaging modality for pre- and postnatal kidney cysts and should also exclude extrarenal manifestations in the abdomen and internal genital organs. MRI has selected indications. Suspicion of a cystic kidney disease should prompt consultation of a pediatric nephrologist. Prenatal management must be tailored to very different degrees of disease severity. After renal oligohydramnios, we recommend delivery in a perinatal center. Neonates should not be denied renal replacement therapy solely because of their age. Children with unilateral multicystic dysplastic kidney do not require routine further imaging or nephrectomy, but long-term nephrology follow-up (as do children with uni- or bilateral kidney hypo-/dysplasia with cysts). ARPKD (autosomal recessive polycystic kidney disease), nephronophthisis, Bardet-Biedl syndrome and HNF1B mutations cause relevant extrarenal disease and genetic testing is advisable. Children with tuberous sclerosis complex, tumor predisposition (e. g. von Hippel Lindau syndrome) or high risk of acquired kidney cysts should have regular ultrasounds. Even asymptomatic children of parents with ADPKD (autosomal dominant PKD) should be monitored for hypertension and proteinuria. Presymptomatic diagnostic ultrasound or genetic examination for ADPKD in minors should only be done after thorough counselling. Simple cysts are very rare in children and ADPKD in a parent should be excluded. Complex renal cysts require further investigation.

The "salt and pepper" pattern on renal ultrasound in a group of children with molecular-proven diagnosis of ciliopathy-related renal diseases

BACKGROUND

While typical ultrasound patterns of ciliopathy-related cystic kidney diseases have been described in children, ultrasound findings can overlap between different diseases and atypical patterns exist. In this study, we assessed the presence of the "salt and pepper" pattern in different renal ciliopathies and looked for additional ultrasound features.

METHODS

This single-center, retrospective study included all patients with a molecular-proven diagnosis of renal ciliopathy, referred to our center between 2007 and 2017. Images from the first and follow-up ultrasound exams were reviewed. Basic ultrasound features were grouped into patterns and compared to genetic diagnoses. The "salt and pepper" aspect was described as enlarged kidneys with heterogeneous, increased parenchymal echogenicity.

RESULTS

A total of 41 children with 5 different renal ciliopathies were included (61% male; median age, 6 years [range, 3 days to 17 years]). The "salt and pepper" pattern was present in 14/15 patients with an autosomal recessive polycystic kidney disease (ARPKD). A similar pattern was found in 1/4 patients with an autosomal dominant polycystic kidney disease and in 1/11 patients with HNF1B mutation. Additional signs found were areas of cortical sparing, comet-tail artifacts, and color comet-tail artifacts.

CONCLUSION

Although the "salt and pepper" ultrasound pattern is predominantly found in ARPKD, it may be detected in other ciliopathies. The color comet-tail artifact is an interesting sign when suspecting a renal ciliopathy in case of enlarged hyperechoic kidneys with no detectable microcysts on B-mode grayscale ultrasound.

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.

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.

Prenatal diagnosis of chromosomal aberrations by chromosomal microarray analysis in fetuses with ultrasound anomalies in the urinary system

OBJECTIVES

This study aimed to explore the relationships between urinary anomalies and copy number variations (CNVs) in fetuses and provide information for prenatal diagnosis and genetic counseling for parents.

METHODS

Three hundred seventeen fetuses with urinary system anomalies detected by prenatal ultrasound were enrolled; 251 had isolated urinary system anomalies, and 66 had nonisolated system anomalies. CMA was performed on the Affymetrix 750K platform.

RESULTS

The frequency of chromosomal aberrations in fetuses with urinary system anomalies was 11.04%, including 6.31% with pathogenic CNVs (pCNVs). The detection rate of chromosomal abnormalities was significantly higher for the fetuses with nonisolated urinary system anomalies than for those with isolated urinary system anomalies. Seven fetuses (25.93%) with echogenic kidneys were identified with pCNVs; this detection rate was significantly higher than that for fetuses with other urinary anomalies. A 17q12 deletion was detected in eight fetuses with urinary anomalies, accounting for 40% of pCNVs.

CONCLUSION

CMA is especially valuable in the prenatal diagnosis of fetuses with urinary system anomalies. The pCNV rates differed between the isolated and nonisolated subgroups of urinary anomalies. Fetuses with echogenic kidneys had the highest rate of pCNVs. The 17q12 deletion was the most frequent pCNV in fetuses with urinary anomalies.

New insights into the role of HNF-1β in kidney (patho)physiology

Hepatocyte nuclear factor-1β (HNF-1β) is an essential transcription factor that regulates the development and function of epithelia in the kidney, liver, pancreas, and genitourinary tract. Humans who carry HNF1B mutations develop heterogeneous renal abnormalities, including multicystic dysplastic kidneys, glomerulocystic kidney disease, renal agenesis, renal hypoplasia, and renal interstitial fibrosis. In the embryonic kidney, HNF-1β is required for ureteric bud branching, initiation of nephrogenesis, and nephron segmentation. Ablation of mouse Hnf1b in nephron progenitors causes defective tubulogenesis, whereas later inactivation in elongating tubules leads to cyst formation due to downregulation of cystic disease genes, including Umod, Pkhd1, and Pkd2. In the adult kidney, HNF-1β controls the expression of genes required for intrarenal metabolism and solute transport by tubular epithelial cells. Tubular abnormalities observed in HNF-1β nephropathy include hyperuricemia with or without gout, hypokalemia, hypomagnesemia, and polyuria. Recent studies have identified novel post-transcriptional and post-translational regulatory mechanisms that control HNF-1β expression and activity, including the miRNA cluster miR17 ∼ 92 and the interacting proteins PCBD1 and zyxin. Further understanding of the molecular mechanisms upstream and downstream of HNF-1β may lead to the development of new therapeutic approaches in cystic kidney disease and other HNF1B-related renal diseases.

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.

Prenatal diagnosis of 17q12 microdeletion and microduplication syndrome in fetuses with congenital renal abnormalities

Background

Copy number variations (CNVs) involving the 17q12 region are associated with a broad range of clinical phenotypes. Deletion of the 17q12 chromosome results in structural or functional abnormalities in the kidney and urethra, type 5 diabetes (MODY5), and neurodevelopmental or neuropsychiatric disorders. Microduplication of 17q12 is rare and is associated with an increased risk of epilepsy and mental retardation. We studied the prenatal diagnosis of 17q12 microduplication and microdeletion syndrome in fetuses with congenital renal abnormalities.

Case presentation

We conducted a retrospective analysis of prenatal diagnoses in our hospital from January 2016 to April 2018. Abnormal renal ultrasound findings were present in 126 fetuses and the incidence of chromosomal abnormalities was 10.32%(13/126). Conventional karyotyping detected 7 of 126 fetuses as aneuploid (5.56%). In addition, chromosome microarray analysis (CMA) detected 6 fetuses(4.76%) with copy number variations (CNVs), of which 5 were shown to have 17q12 microdeletion syndrome and 1 had 17q12 microduplication syndrome. We followed up these pregnant women. The results of the testing had a significant impact on pregnancy outcome. The phenotypes of 17q12 microdeletions and microduplications vary widely, affecting patients in different ways, such as language delays, social deficiencies, and even abortion.

Conclusions

The characteristics of 17q12 microdeletions and microduplications are so vague that the condition is often misdiagnosed or missed. This study demonstrated that karyotype analysis combined with CMA can significantly improve the diagnostic rate in prenatal diagnosis of CNVs, which can provide evidence for genetic counseling in such pregnancies.