Outcome of infantile nephropathic cystinosis depends on early intervention, not genotype: A multicenter sibling cohort study.

Infantile nephropathic cystinosis (INC) is an inheritable lysosomal storage disorder characterized by lysosomal cystine accumulation, progressive kidney disease, and multiple extrarenal complications (ERCs). Cysteamine postpones the onset of end-stage kidney disease (ESKD) and reduces the incidence of ERCs; however, cysteamine is generally initiated upon establishment of the renal Fanconi syndrome (FS) and partial loss of kidney function, whereas data on long-term effects of cysteamine administered from neonatal age are lacking. An international multicenter retrospective cohort study of siblings with INC was set up to investigate the outcome in relation to age at initiation of cysteamine versus CTNS genotype, with attention to patients treated with cysteamine from neonatal age. None of the siblings treated from neonatal age (n = 9; age 10 ± 6 years) had reached ESKD, while 22% of their index counterparts (n = 9; age 14 ± 5 years) had commenced renal replacement therapy. Siblings treated with cysteamine from the onset of symptoms at a younger age compared with their index counterparts, reached ESKD at a significant older age (13 ± 3 vs. 10 ± 3 years, p = 0.002). In contrast, no significant difference in ERCs was observed between sibling and index patients, independently from the age at initiation of cysteamine. The CTNS genotype had no impact on the overall outcome in this cohort. In INC, presymptomatic treatment with cysteamine results in a better renal outcome in comparison to treatment initiated from the onset of symptoms. This justifies including cystinosis into newborn screening programs. SYNOPSIS: In infantile nephropathic cystinosis, presymptomatic treatment with cysteamine improves the renal outcome which justifies the inclusion of cystinosis into newborn screening programs.

Molecular Basis of Cystinosis: Geographic Distribution, Functional Consequences of Mutations in the CTNS Gene, and Potential for Repair.

Mutations in the CTNS gene encoding the lysosomal membrane cystine transporter cystinosin are the cause of cystinosis, an autosomal recessive lysosomal storage disease. More than 140 CTNS mutations have been reported worldwide. Recent studies have discovered that cystinosin exerts other key cellular functions beyond cystine transport such as regulation of oxidative state, lysosomal dynamics and autophagy. Here, we review the different mutations described in the CTNS gene and the geographical distribution of incidence. In addition, the characteristics of the various mutations in relation to the functions of cystinosin needs to be further elucidated. In this review, we highlight the functional consequences of the different mutations in correlation with the clinical phenotypes. Moreover, we propose how this understanding would be fundamental for the development of new technologies through targeted gene therapy, holding promises for a possible cure of the kidney and extra-renal phenotypes of cystinosis.

18F-FDG-PET/CT for the detection of disease in patients with head and neck cancer treated with radiotherapy.

OBJECTIVE: The aim of this study is to evaluate the diagnostic performance of FDG-PET/CT for the detection of residual disease after (chemo)radiotherapy in patients with head and neck squamous cell carcinoma (HNSCC) and to evaluate the prognostic value of the FDG-PET/CT findings. METHODS: Patients with HNSCC who underwent FDG-PET/CT after (chemo)radiotherapy were studied retrospectively. RESULTS: 104 FDG-PET/CT-scans were performed at a median of 13.2 weeks post-treatment (5.4-19.0 weeks). The diagnostic performance was time dependent with decreasing sensitivity and slightly increasing specificity over time. Sensitivity, specificity, PPV and NPV at 9 months after imaging were 91%, 87%, 77% and 95%, respectively. In a logistic regression model, the odds of a correct FDG-PET/CT increased with 33% every additional week after end of therapy (p = 0.01) and accuracy plateaued after 11 weeks (97%; p<0.001). A complete response on FDG-PET/CT was associated with an overall survival benefit (50.7 versus 10.3 months; p<0.001). Residual disease on FDG-PET/CT increased the risk of death 8-fold (p<0.001). CONCLUSION: FDG-PET/CT is able to detect residual disease after (chemo)radiotherapy, with an optimal time point for scanning between 11-12 weeks after therapy. However, a reevaluation is probably necessary 10-12 months after the FDG-PET/CT to detect late recurrences. In addition, FDG-PET/CT can guide decisions about neck dissection and identifies patients with poor prognosis.

Iron refractory iron deficiency anemia: a heterogeneous disease that is not always iron refractory.

TMPRSS6 variants that affect protein function result in impaired matriptase-2 function and consequently uninhibited hepcidin production, leading to iron refractory iron deficiency anemia (IRIDA). This disease is characterized by microcytic, hypochromic anemia and serum hepcidin values that are inappropriately high for body iron levels. Much is still unknown about its pathophysiology, genotype-phenotype correlation, and optimal clinical management. We describe 14 different TMPRSS6 variants, of which 9 are novel, in 21 phenotypically affected IRIDA patients from 20 families living in the Netherlands; 16 out of 21 patients were female. In 7 out of 21 cases DNA sequencing and multiplex ligation dependent probe amplification demonstrated only heterozygous TMPRSS6 variants. The age at presentation, disease severity, and response to iron supplementation were highly variable, even for patients and relatives with similar TMPRSS6 genotypes. Mono-allelic IRIDA patients had a milder phenotype with respect to hemoglobin and MCV and presented significantly later in life with anemia than bi-allelic patients. Transferrin saturation (TSAT)/hepcidin ratios were lower in IRIDA probands than in healthy relatives. Most patients required parenteral iron. Genotype alone was not predictive for the response to oral iron. We conclude that IRIDA is a genotypically and phenotypically heterogeneous disease. The high proportion of female patients and the discrepancy between phenotypes of probands and relatives with the same genotype, suggest a complex interplay between genetic and acquired factors in the pathogenesis of IRIDA. In the absence of inflammation, the TSAT/hepcidin ratio is a promising diagnostic tool, even after iron supplementation has been given. Am. J. Hematol. 91:E482-E490, 2016. © 2016 Wiley Periodicals, Inc.

A post-hoc comparison of the utility of sanger sequencing and exome sequencing for the diagnosis of heterogeneous diseases.

The advent of massive parallel sequencing is rapidly changing the strategies employed for the genetic diagnosis and research of rare diseases that involve a large number of genes. So far it is not clear whether these approaches perform significantly better than conventional single gene testing as requested by clinicians. The current yield of this traditional diagnostic approach depends on a complex of factors that include gene-specific phenotype traits, and the relative frequency of the involvement of specific genes. To gauge the impact of the paradigm shift that is occurring in molecular diagnostics, we assessed traditional Sanger-based sequencing (in 2011) and exome sequencing followed by targeted bioinformatics analysis (in 2012) for five different conditions that are highly heterogeneous, and for which our center provides molecular diagnosis. We find that exome sequencing has a much higher diagnostic yield than Sanger sequencing for deafness, blindness, mitochondrial disease, and movement disorders. For microsatellite-stable colorectal cancer, this was low under both strategies. Even if all genes that could have been ordered by physicians had been tested, the larger number of genes captured by the exome would still have led to a clearly superior diagnostic yield at a fraction of the cost.

Long-term outcome of biopsy-proven, frequently relapsing minimal-change nephrotic syndrome in children.

BACKGROUND AND OBJECTIVES: Frequently relapsing and steroid-dependent minimal-change nephrotic syndrome (MCNS) that originates in childhood can persist after puberty in >20% of patients. These patients require immunosuppressive treatment during several decades of their life. We examined long-term adverse effects of persistent nephrotic syndrome and immunosuppressive medications, focusing on renal function, growth, obesity, osteoporosis, hypertension, ocular complications, and fertility in adult patients with biopsy-proven childhood-onset MCNS. Molecular analysis was performed to evaluate a possible association of a complicated course of MCNS with podocyte gene mutations. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We performed a prospective clinical examination of 15 adult patients that included serum and urine analysis; dual-energy x-ray absorptiometry; ophthalmologic examination; semen examination; and molecular analysis of NPHS1, NPHS2, CD2AP, and ACTN4 genes. RESULTS: All patients had normal GFR. Most frequent long-term complications were hypertension (in seven of 15 patients) and osteoporosis in one third of patients. Oligozoospermia was found in one patient, reduced sperm motility in four of eight patients, and teratozoospermia in six of eight patients. Ophthalmologic examination revealed myopia in 10 of 15 patients and cataract in three of 15 patients. CONCLUSIONS: Children with MCNS that persists after puberty are at risk for complications such as osteoporosis, hypertension, cataract, and sperm abnormalities. Our study underscores a need for more effective and less toxic therapies for relapsing MCNS.

Distinct clinical phenotypes associated with a mutation in the mitochondrial translation elongation factor EFTs.

The 13 polypeptides encoded in mitochondrial DNA (mtDNA) are synthesized in the mitochondrial matrix on a dedicated protein-translation apparatus that resembles that found in prokaryotes. Here, we have investigated the genetic basis for a mitochondrial protein-synthesis defect associated with a combined oxidative phosphorylation enzyme deficiency in two patients, one of whom presented with encephalomyopathy and the other with hypertrophic cardiomyopathy. Sequencing of candidate genes revealed the same homozygous mutation (C997T) in both patients in TSFM, a gene coding for the mitochondrial translation elongation factor EFTs. EFTs functions as a guanine nucleotide exchange factor for EFTu, another translation elongation factor that brings aminoacylated transfer RNAs to the ribosomal A site as a ternary complex with guanosine triphosphate. The mutation predicts an Arg333Trp substitution at an evolutionarily conserved site in a subdomain of EFTs that interacts with EFTu. Molecular modeling showed that the substitution disrupts local subdomain structure and the dimerization interface. The steady-state levels of EFTs and EFTu in patient fibroblasts were reduced by 75% and 60%, respectively, and the amounts of assembled complexes I, IV, and V were reduced by 35%-91% compared with the amounts in controls. These phenotypes and the translation defect were rescued by retroviral expression of either EFTs or EFTu. These data clearly establish mutant EFTs as the cause of disease in these patients. The fact that the same mutation is associated with distinct clinical phenotypes suggests the presence of genetic modifiers of the mitochondrial translation apparatus.

Human mitochondrial complex I assembles through the combination of evolutionary conserved modules: a framework to interpret complex I deficiencies.

With 46 subunits, human mitochondrial complex I is the largest enzyme of the oxidative phosphorylation system. We have studied the assembly of complex I in cultured human cells. This will provide essential information about the nature of complex I deficiencies and will enhance our understanding of mitochondrial disease mechanisms. We have found that 143B206 rho zero cells, not containing mitochondrial DNA, are still able to form complex I subcomplexes. To further address the nature of these subcomplexes, we depleted 143B osteosarcoma cells of complex I by inhibiting mitochondrial protein translation with doxycycline. After removing this drug, complex I formation resumes and assembly intermediates were observed by two-dimensional blue native electrophoresis. Analysis of the observed subcomplexes indicates that assembly of human complex I is a semi-sequential process in which different preassembled subcomplexes are joined to form a fully assembled complex. The membrane part of the complex is formed in distinct steps. The B17 subunit is part of a subcomplex to which ND1, ND6 and PSST are subsequently added. This is bound to a hydrophilic subcomplex containing the 30 and 49 kDa subunits, to which a subcomplex including the 39 kDa subunit is incorporated, and later on the 18 and 24 kDa subunits. At a later stage more subunits, including the 15 kDa, are added and holo-complex I is formed. Our results suggest that human complex I assembly resembles that of Neurospora crassa, in which a membrane arm is formed and assembled to a preformed peripheral arm, and support ideas about modular evolution.