A description of a fetal syndrome associated with HNF1B mutation and a wide intrafamilial disease variability

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.

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.

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.

Targeted gene sequencing and whole-exome sequencing in autopsied fetuses with prenatally diagnosed kidney anomalies

Identification of fetal kidney anomalies invites questions about underlying causes and recurrence risk in future pregnancies. We therefore investigated the diagnostic yield of next-generation sequencing in fetuses with bilateral kidney anomalies and the correlation between disrupted genes and fetal phenotypes. Fetuses with bilateral kidney anomalies were screened using an in-house-designed kidney-gene panel. In families where candidate variants were not identified, whole-exome sequencing was performed. Genes uncovered by this analysis were added to our kidney panel. We identified likely deleterious variants in 11 of 56 (20%) families. The kidney-gene analysis revealed likely deleterious variants in known kidney developmental genes in 6 fetuses and TMEM67 variants in 2 unrelated fetuses. Kidney histology was similar in the latter 2 fetuses-presenting a distinct prenatal form of nephronophthisis. Exome sequencing identified ROBO1 variants in one family and a GREB1L variant in another family. GREB1L and ROBO1 were added to our kidney-gene panel and additional variants were identified. Next-generation sequencing substantially contributes to identifying causes of fetal kidney anomalies. Genetic causes may be supported by histological examination of the kidneys. This is the first time that SLIT-ROBO signaling is implicated in human bilateral kidney agenesis.

HNF1B-associated clinical phenotypes: the kidney and beyond

Mutations in HNF1B, the gene encoding hepatocyte nuclear factor 1β are the most commonly identified genetic cause of renal malformations. HNF1B was first identified as a disease gene for diabetes (MODY5) in 1997, and its involvement in renal disease was subsequently noted through clinical observations in pedigrees affected by MODY5. Since then, a whole spectrum of associated phenotypes have been reported, including genital malformations, autism, epilepsy, gout, hypomagnesaemia, primary hyperparathyroidism, liver and intestinal abnormalities and a rare form of kidney cancer. The most commonly identified mutation, in approximately 50 % of patients, is an entire gene deletion occurring in the context of a 17q12 chromosomal microdeletion that also includes several other genes. Some of the associated phenotypes, especially the neurologic ones, appear to occur only in the context of this microdeletion and thus may not be directly linked to HNF1B. Here we review the spectrum of associated phenotypes and discuss potential implications for clinical management.

A novel mutation of the HNF1B gene associated with hypoplastic glomerulocystic kidney disease and neonatal renal failure: a case report and mutation update

Hepatocyte nuclear factor 1 beta (HNF1B) plays an important role in embryonic development, namely in the kidney, pancreas, liver, genital tract, and gut. Heterozygous germline mutations of HNF1B are associated with the renal cysts and diabetes syndrome (RCAD). Affected individuals may present a variety of renal developmental abnormalities and/or maturity-onset diabetes of the young (MODY). A Portuguese 19-month-old male infant was evaluated due to hypoplastic glomerulocystic kidney disease and renal dysfunction diagnosed in the neonatal period that progressed to stage 5 chronic renal disease during the first year of life. His mother was diagnosed with a solitary hypoplastic microcystic left kidney at age 20, with stage 2 chronic renal disease established at age 35, and presented bicornuate uterus, pancreatic atrophy, and gestational diabetes. DNA sequence analysis of HNF1B revealed a novel germline frameshift insertion (c.110_111insC or c.110dupC) in both the child and the mother. A review of the literature revealed a total of 106 different HNF1B mutations, in 236 mutation-positive families, comprising gross deletions (34%), missense mutations (31%), frameshift deletions or insertions (15%), nonsense mutations (11%), and splice-site mutations (8%). The study of this family with an unusual presentation of hypoplastic glomerulocystic kidney disease with neonatal renal dysfunction identified a previously unreported mutation of the HNF1B gene, thereby expanding the spectrum of known mutations associated with renal developmental disorders.

Criteria for HNF1B analysis in patients with congenital abnormalities of kidney and urinary tract

BACKGROUND

Congenital anomalies of kidneys and urinary tract (CAKUT) are the most predominant developmental disorders comprising ∼20-30% of all anomalies identified in the prenatal period. Mutations in hepatocyte nuclear factor 1-beta (HNF-1β) involved in the development of kidneys, liver, pancreas and urogenital tract are currently the most frequent monogenetic cause of CAKUT found in 10-30% of patients depending on screening policy and study design. We aimed to validate criteria for analysis of HNF1B in a prospective cohort of paediatric and adult CAKUT patients.

METHODS

We included CAKUT patients diagnosed in our paediatric and adult nephrology departments from January 2010 until April 2013 based on predefined screening criteria. Subjects presenting with at least one major renal criterion or one minor renal criterion combined with one or more extra-renal criteria in the personal history or a familial history of renal or extra-renal manifestations were considered eligible.

RESULTS

We prospectively screened 205 patients and detected HNF1B mutations in 10% [n = 20, 12 children, median age 4.2 (range 0-13.1) years and 8 adults, median age 34.8 (range 16.6-62) years]. We observed that bilateral renal anomaly, renal cysts from unknown origin, a combination of two major renal anomalies and hypomagnesaemia were predictive for finding HNF1B mutations (P < 0.001; P < 0.001; P = 0.004; P = 0.008, respectively).

CONCLUSIONS

We demonstrated that HNF1B mutations are responsible for ∼10% of CAKUT cases, both in children and in adults. Based on our results we propose adapted criteria for HNF1B analysis to reduce the screening costs without missing affected patients. These criteria should be reaffirmed in a larger validation cohort.