Genetic and molecular studies in Hyperinsulinemic Hypoglycemia and congenital Polycystic Kidney Disease (HIPKD)

Background: Hyperinsulinemic hypoglycemia (HI) and congenital polycystic kidney disease (PKD) are rare, genetically heterogeneous disorders. The co-occurrence (HIPKD) in 17 children from 11 unrelated families suggested a shared cause. // Methods: We ascertained the clinical phenotype and performed genetic studies. The effect of the identified shared mutation was assessed in vitro. // Results: All patients exhibited HI and enlarged polycystic kidneys. Whole genome linkage analysis in 5 informative families identified a single significant (LOD 6.5) locus on chromosome 16p13.2. A promoter mutation (c.-167G>T) in PMM2 was found in all patients, either homozygous or in trans with PMM2 coding mutations. Yet, typical systemic features of congenital disorder of glycosylation type 1a were absent and the diagnostic test of transferrin isoelectric focusing was normal. The promoter mutation showed decreased transcriptional activity in patient kidney cells and impaired binding of the transcription factor ZNF143. In silico analysis suggests an important role for ZNF143 for the formation of a chromatin loop including PMM2 that could affect tissue-specific transcription. In order to investigate this further in a chromatin conformation study a HIPKD cell model homozygous for the promoter mutation was generated with CRISPR-Cas9. // Conclusions: We report a rare disease characterized by the combination of hyperinsulinemic hypoglycemia and polycystic kidney disease. Our findings extend the spectrum of genetic causes for both disorders, provide insights into gene regulation and implicate glycosylation in the disease etiology. The identified promoter mutation appears critical for tissue-specific regulation of PMM2 transcription, leading to an organ-specific phenotype and explaining PMM2 pleiotropy

HTA programme response to the challenges of dealing with orphan medicinal products:Process evaluation in selected European countries

Background Challenges commonly encountered in HTA of orphan medicinal products (OMPs) were identified in Advance-HTA. Since then, new initiatives have been developed to specifically address issues related to HTA of OMPs. Objective and methods This study aimed to understand why these new HTA initiatives in England, Scotland and at European-level were established and whether they resolve the challenges of OMPs. The work of Advance-HTA was updated with a literature review and a conceptual framework of clinical, regulatory and economic challenges for OMPs was developed. The new HTA programmes were critiqued against the conceptual framework and outstanding challenges identified. Results The new programmes in England and Scotland recognise the challenges identified in demonstrating the value of ultra-OMPs (and OMPs) and that they require a different process to standard HTA approaches. Wider considerations of disease and treatment experiences from a multi-stakeholder standpoint are needed, combined with other measures to deal with uncertainty (e.g. managed entry agreements). While approaches to assessing this new view of value of OMPs, extending beyond cost/QALY frameworks, differ, their criteria are similar. These are complemented by a European initiative that fosters multi-stakeholder dialogue and consensus about value determinants throughout the life-cycle of an OMP. Conclusion New HTA programmes specific to OMPs have been developed but questions remain about whether they sufficiently capture value and manage uncertainty in clinical practice

Molecular Basis for Autosomal-Dominant Renal Fanconi Syndrome Caused by HNF4A

International audienceHNF4A is a nuclear hormone receptor that binds DNA as an obligate homodimer. While all known human heterozygous mutations are associated with the autosomal-dominant diabetes form MODY1, one particular mutation (p.R85W) in the DNA-binding domain (DBD) causes additional renal Fanconi syndrome (FRTS). Here, we find that expression of the conserved fly ortholog dHNF4 harboring the FRTS mutation in Drosophila nephrocytes caused nuclear depletion and cytosolic aggregation of a wild-type dHNF4 reporter protein. While the nuclear depletion led to mitochondrial defects and lipid droplet accumulation, the cytosolic aggregates triggered the expansion of the endoplasmic reticulum (ER), autophagy, and eventually cell death. The latter effects could be fully rescued by preventing nuclear export through interfering with serine phosphorylation in the DBD. Our data describe a genomic and a non-genomic mechanism for FRTS in HNF4A-associated MODY1 with important implications for the renal proximal tubule and the regulation of other nuclear hormone receptors

Phase II trial of continuous low-dose temozolomide for patients with recurrent malignant glioma

Background In this phase II trial, we investigated the efficacy of a metronomic temozolomide schedule in the treatment of recurrent malignant gliomas (MGs).Methods Eligible patients received daily temozolomide (50 mg/m2) continuously until progression. The primary endpoint was progression-free survival rate at 6 months in the glioblastoma cohort (N = 37). In an exploratory analysis, 10 additional recurrent grade III MG patients were enrolled. Correlative studies included evaluation of 76 frequent mutations in glioblastoma (iPLEX assay, Sequenom) aiming at establishing the frequency of potentially &ldquo;drugable&rdquo; mutations in patients entering recurrent MG clinical trials.Results Among glioblastoma patients, median age was 56 y; median Karnofsky Performance Score (KPS) was 80; 62% of patients had been treated for &ge;2 recurrences, including 49% of patients having failed bevacizumab. Treatment was well tolerated; clinical benefit (complete response + partial response + stable disease) was seen in 10 (36%) patients. Progression-free survival rate at 6 months was 19% and median overall survival was 7 months. Patients with previous bevacizumab exposure survived significantly less than bevacizumab-naive patients (median overall survival: 4.3 mo vs 13 mo; hazard ratio = 3.2; P = .001), but those patients had lower KPS (P = .04) and higher number of recurrences (P &lt; .0001). Mutations were found in 13 of the 38 MGs tested, including mutations of EGFR (N = 10), IDH1 (N = 5), and ERBB2 (N = 1).Conclusions In spite of a heavily pretreated population, including nearly half of patients having failed bevacizumab, the primary endpoint was met, suggesting that this regimen deserves further investigation. Results in bevacizumab-naive patients seemed particularly favorable, while results in bevacizumab-failing patients highlight the need to develop further treatment strategies for advanced MG.<br /

A Founder Mutation in EHD1 Presents with Tubular Proteinuria and Deafness

Background The endocytic reabsorption of proteins in the proximal tubule requires a complex machinery and defects can lead to tubular proteinuria. The precise mechanisms of endocytosis and processing of receptors and cargo are incompletely understood. EHD1 belongs to a family of proteins presumably involved in the scission of intracellular vesicles and in ciliogenesis. However, the relevance of EHD1 in human tissues, in particular in the kidney, was unknown. Methods Genetic techniques were used in patients with tubular proteinuria and deafness to identify the disease-causing gene. Diagnostic and functional studies were performed in patients and disease models to investigate the pathophysiology. Results We identified six individuals (5–33 years) with proteinuria and a high-frequency hearing deficit associated with the homozygous missense variant c.1192C>T (p.R398W) in EHD1. Proteinuria (0.7–2.1 g/d) consisted predominantly of low molecular weight proteins, reflecting impaired renal proximal tubular endocytosis of filtered proteins. Ehd1 knockout and Ehd1R398W/R398W knockin mice also showed a high-frequency hearing deficit and impaired receptor-mediated endocytosis in proximal tubules, and a zebrafish model showed impaired ability to reabsorb low molecular weight dextran. Interestingly, ciliogenesis appeared unaffected in patients and mouse models. In silico structural analysis predicted a destabilizing effect of the R398W variant and possible inference with nucleotide binding leading to impaired EHD1 oligomerization and membrane remodeling ability. Conclusions A homozygous missense variant of EHD1 causes a previously unrecognized autosomal recessive disorder characterized by sensorineural deafness and tubular proteinuria. Recessive EHD1 variants should be considered in individuals with hearing impairment, especially if tubular proteinuria is noted

Polycystic kidney disease with hyperinsulinemic hypoglycemia caused by a promoter mutation in phosphomannomutase 2.

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Hyperinsulinemic hypoglycemia (HI) and congenital polycystic kidney disease (PKD) are rare, genetically heterogeneous disorders. The co-occurrence of these disorders (HIPKD) in 17 children from 11 unrelated families suggested an unrecognized genetic disorder. Whole-genome linkage analysis in five informative families identified a single significant locus on chromosome 16p13.2 (logarithm of odds score 6.5). Sequencing of the coding regions of all linked genes failed to identify biallelic mutations. Instead, we found in all patients a promoter mutation (c.-167G>T) in the phosphomannomutase 2 gene (PMM2), either homozygous or in trans with PMM2 coding mutations. PMM2 encodes a key enzyme in N-glycosylation. Abnormal glycosylation has been associated with PKD, and we found that deglycosylation in cultured pancreatic β cells altered insulin secretion. Recessive coding mutations in PMM2 cause congenital disorder of glycosylation type 1a (CDG1A), a devastating multisystem disorder with prominent neurologic involvement. Yet our patients did not exhibit the typical clinical or diagnostic features of CDG1A. In vitro, the PMM2 promoter mutation associated with decreased transcriptional activity in patient kidney cells and impaired binding of the transcription factor ZNF143. In silico analysis suggested an important role of ZNF143 for the formation of a chromatin loop including PMM2 We propose that the PMM2 promoter mutation alters tissue-specific chromatin loop formation, with consequent organ-specific deficiency of PMM2 leading to the restricted phenotype of HIPKD. Our findings extend the spectrum of genetic causes for both HI and PKD and provide insights into gene regulation and PMM2 pleiotropy.This work was supported by the Medical Research Council (Grant Number 98144), the Great Ormond Street Hospital Children’s Charity, Kids Kidney Research, St Peter’s Trust for Kidney, Bladder and Prostate Research, The David and Elaine Potter Foundation and the European Union, FP7 (grant agreement 2012-305608 “European Consortium for High-Throughput Research in Rare Kidney Diseases (EURenOmics”). SEF has a Sir Henry Dale Fellowship jointly funded by the Wellcome Trust and the Royal Society (Grant Number: 105636/Z/14/Z). SE is a Wellcome Trust Senior Investigator

Glycine Amidinotransferase (GATM), Renal Fanconi Syndrome, and Kidney Failure

Background For many patients with kidney failure, the cause and underlying defect remain unknown. Here, we describe a novel mechanism of a genetic order characterized by renal Fanconi syndrome and kidney failure. Methods We clinically and genetically characterized members of five families with autosomal dominant renal Fanconi syndrome and kidney failure. We performed genome-wide linkage analysis, sequencing, and expression studies in kidney biopsy specimens and renal cells along with knockout mouse studies and evaluations of mitochondrial morphology and function. Structural studies examined the effects of recognized mutations. Results The renal disease in these patients resulted from monoallelic mutations in the gene encoding glycine amidinotransferase (GATM), a renal proximal tubular enzyme in the creatine biosynthetic pathway that is otherwise associated with a recessive disorder of creatine deficiency. In silico analysis showed that the particular GATM mutations, identified in 28 members of the five families, create an additional interaction interface within the GATM protein and likely cause the linear aggregation of GATM observed in patient biopsy specimens and cultured proximal tubule cells. GATMaggregates-containing mitochondria were elongated and associated with increased ROS production, activation of the NLRP3 inflammasome, enhanced expression of the profibrotic cytokine IL-18, and increased cell death. Conclusions In this novel genetic disorder, fully penetrant heterozygous missense mutations in GATM trigger intramitochondrial fibrillary deposition of GATM and lead to elongated and abnormal mitochondria. We speculate that this renal proximal tubular mitochondrial pathology initiates a response from the inflammasome, with subsequent development of kidney fibrosis