Synthesis and Macrodomain Binding of Gln-carba-ADPr-peptide.

Mono-ADP-ribosylation is a dynamic post-translational modification (PTM) with important roles in cell signalling. This modification occurs on a wide variety of amino acids, and one of the canonical modification sites within proteins is the side chain of glutamic acid. Given the transient nature of this modification (acylal linkage) and the high sensitivity of ADP-ribosylated glutamic acid, stabilized isosteres are required for structural and biochemical studies. Here, we report the synthesis of a mimic of ADP-ribosylated peptide derived from histone H2B that contains carba-ADP-ribosylated glutamine as a potential mimic for Glu-ADPr. We synthesized a cyclopentitol-ribofuranosyl derivative of 5'-phosphoribosylated Fmoc-glutamine and used this in the solid-phase synthesis of the carba-ADPr-peptide mimicking the ADP-ribosylated N-terminal tail of histone H2B. Binding studies with isothermal calorimetry demonstrate that the macrodomains of human MacroD2 and TARG1 bind to carba-ADPr-peptide in the same way as ADPr-peptides containing the native ADP-riboside moiety connected to the side chain of glutamine in the same peptide sequence.

Long-term Outcomes Following Active Surveillance of Low-grade Prostate Cancer: A Population-based Study Using a Landmark Approach.

PURPOSE: Active surveillance is widely used to manage low-risk prostate cancer, but population-level long-term outcomes are limited. Our objective was to determine long-term population-level oncological outcomes in active surveillance patients. A secondary objective examined the active surveillance discontinuation rate. MATERIALS AND METHODS: In this retrospective, population-based study using linked administrative databases from Ontario, Canada, we identified low-grade prostate cancer patients managed with active surveillance or initial treatment between 2002-2014. The 10- and 15-year metastasis-free survival, overall survival, and cancer-specific survival were compared between active surveillance and initial treatment. A landmark of 24 months was selected for the primary analysis. Long-term outcomes were examined using multivariable proportional hazards models and a propensity-based approach. RESULTS: The cohort consisted of 21,282 low-grade prostate cancer patients with a median follow-up of 9.8 years. At 10-year follow-up the survival rate of remaining on active surveillance was 39%, metastasis-free survival was 94.2%, overall survival 88.7%, and cancer-specific survival 98.1%. In adjusted models active surveillance was associated with higher risk of metastasis (HR 1.34, 95%CI 1.15-1.57), overall mortality (HR 1.12, 95%CI 1.01-1.24), and prostate cancer-specific mortality (HR 1.66, 95%CI 1.15-2.39) compared to initial treatment. Survival analysis using 7,525 propensity-matched pairs was consistent with the primary analysis for metastasis-free survival, overall survival and cancer-specific survival. CONCLUSIONS: In this large population-based study of long-term outcomes in men with low-grade prostate cancer, active surveillance is associated with excellent long-term metastasis-free survival and overall survival. However, long-term cancer-specific survival was slightly inferior (1% worse at 10 years with active surveillance), and this must be balanced against known harms of overtreatment.

[Severe polyneuropathy in primary Sjögren's syndrome : Sjögren's syndrome should be considered in patients with motor neuropathy]. / Schwere Polyneuropathie bei primärem Sjögren-Syndrom : Bei Patienten mit motorischen Neuropathien auch an Sjögren-Syndrom denken!

A 64-year-old male patient developed over a period of 20 years a peripheral neuropathy symmetrically affecting the upper and lower limbs. The histological examination of a sural nerve biopsy revealed a severe axonal neuropathy. Despite extensive laboratory investigations including immunological and metabolic tests the origin could not be identified. Finally, a Schirmer test revealed xerophthalmia. A subsequent salivary gland biopsy from the lower lip revealed a grade III lymphocytic inflammation according to Chisholm and Mason and confirmed the diagnosis of Sjögren's syndrome.

Human prostate luminal cell differentiation requires NOTCH3 induction by p38-MAPK and MYC.

Many pathways dysregulated in prostate cancer are also involved in epithelial differentiation. To better understand prostate tumor initiation, we sought to investigate specific genes and mechanisms required for normal basal to luminal cell differentiation. Utilizing human prostate basal epithelial cells and an in vitro differentiation model, we tested the hypothesis that regulation of NOTCH3 by the p38 MAPK family (hereafter p38-MAPK), via MYC, is required for luminal differentiation. Inhibition (SB202190 and BIRB796) or knockdown of p38α (also known as MAPK14) and/or p38δ (also known as MAPK13) prevented proper differentiation. Additionally, treatment with a γ-secretase inhibitor (RO4929097) or knockdown of NOTCH1 and/or NOTCH3 greatly impaired differentiation and caused luminal cell death. Constitutive p38-MAPK activation through MKK6(CA) increased NOTCH3 (but not NOTCH1) mRNA and protein levels, which was diminished upon MYC inhibition (10058-F4 and JQ1) or knockdown. Furthermore, we validated two NOTCH3 enhancer elements through a combination of enhancer (e)RNA detection (BruUV-seq) and luciferase reporter assays. Finally, we found that the NOTCH3 mRNA half-life increased during differentiation or upon acute p38-MAPK activation. These results reveal a new connection between p38-MAPK, MYC and NOTCH signaling, demonstrate two mechanisms of NOTCH3 regulation and provide evidence for NOTCH3 involvement in prostate luminal cell differentiation.

Development and validation of the mastocytosis activity score.

BACKGROUND: Mastocytosis is a heterogeneous disease characterized by a clonal expansion of mast cells in various organs. The vast majority of patients suffer from signs and symptoms caused by mediator release from mast cells. Although the disease burden is high, there is currently no specific and validated instrument to measure and monitor signs and symptoms in patients with mastocytosis. OBJECTIVE: To develop and validate a disease-specific tool to measure and monitor the activity of signs and symptoms in patients with mastocytosis, the Mastocytosis Activity Score (MAS). METHODS: Nineteen potential MAS items were developed in a combined approach consisting of semi-structured patient interviews, expert input and literature research. Item selection was performed by impact analysis with 76 patients followed by a review for face validity. The resulting MAS was tested for validity, reliability and influence factors. In parallel, a US American English version of the MAS was developed. RESULTS: A total of 68 mastocytosis patients took part in the MAS validation study. The final 9-item MAS was found to have a three-domain structure ("skin," "gastrointestinal tract" and "other"), a valid total score and an excellent test-retest reliability. Multiple regression analysis revealed that disease duration, age or gender is not a significant determinant of the MAS results. CONCLUSIONS: The MAS is a disease-specific, valid and reliable patient-reported outcome measure for adult patients with cutaneous and indolent systemic mastocytosis. It may serve as a valuable tool to measure and monitor mastocytosis activity, both, in clinical trials and in routine care.

A streamlined method for the design and cloning of shRNAs into an optimized Dox-inducible lentiviral vector.

BACKGROUND: Short hairpin RNA (shRNA) is an established and effective tool for stable knock down of gene expression. Lentiviral vectors can be used to deliver shRNAs, thereby providing the ability to infect most mammalian cell types with high efficiency, regardless of proliferation state. Furthermore, the use of inducible promoters to drive shRNA expression allows for more thorough investigations into the specific timing of gene function in a variety of cellular processes. Moreover, inducible knockdown allows the investigation of genes that would be lethal or otherwise poorly tolerated if constitutively knocked down. Lentiviral inducible shRNA vectors are readily available, but unfortunately the process of cloning, screening, and testing shRNAs can be time-consuming and expensive. Therefore, we sought to refine a popular vector (Tet-pLKO-Puro) and streamline the cloning process with efficient protocols so that researchers can more efficiently utilize this powerful tool. METHODS: First, we modified the Tet-pLKO-Puro vector to make it easy ("EZ") for molecular cloning (EZ-Tet-pLKO-Puro). Our primary modification was to shrink the stuffer region, which allows vector purification via polyethylene glycol precipitation thereby avoiding the need to purify DNA through agarose. In addition, we generated EZ-Tet-pLKO vectors with hygromycin or blasticidin resistance to provide greater flexibility in cell line engineering. Furthermore, we provide a detailed guide for utilizing these vectors, including shRNA design strategy and simplified screening methods. RESULTS: Notably, we emphasize the importance of loop sequence design and demonstrate that the addition of a single mismatch in the loop stem can greatly improve shRNA efficiency. Lastly, we display the robustness of the system with a doxycycline titration and recovery time course and provide a cost/benefit analysis comparing our system with purchasing pre-designed shRNA vectors. CONCLUSIONS: Our aim was twofold: first, to take a very useful shRNA vector and make it more amenable for molecular cloning and, secondly, to provide a streamlined protocol and rationale for cost-effective design, cloning, and screening of shRNAs. With this knowledge, anyone can take advantage of this powerful tool to inducibly knockdown any gene of their choosing.

Early stages in the ontogeny of small B-cell lymphomas: genetics and microenvironment.

In this review, we focus on the mechanisms underlying lymphomagenesis in chronic lymphocytic leukaemia, follicular lymphoma, mantle cell lymphoma and splenic marginal zone lymphoma. The cells of origin of these small B-cell lymphomas are distinct, as are the characteristic chromosomal lesions and clinical courses. One shared feature is retention of expression of surface immunoglobulin. Analysis of this critical receptor reveals the point of differentiation reached by the cell of origin. Additionally, the sequence patterns of the immunoglobulin-variable domains can indicate a role for stimulants of the B-cell receptor before, during and after malignant transformation. The pathways driven via the B-cell receptor are now being targeted by specific kinase inhibitors with exciting clinical effects. To consider routes to pathogenesis, potentially offering earlier intervention, or to identify causative factors, genetic tools are being used to track pretransformation events and the early phases in lymphomagenesis. These methods are revealing that chromosomal changes are only one of the many steps involved, and that the influence of surrounding cells, probably multiple and variable according to tissue location, is required, both to establish tumours and to maintain growth and survival. Similarly, the influence of the tumour microenvironment may protect malignant cells from eradication by treatment, and the resulting minimal residual disease will eventually give rise to relapse. The common and different features of the four lymphomas will be summarized to show how normal B lymphocytes can be subverted to generate tumours, how these tumours evolve and how their weaknesses can be attacked by targeted therapies.

Cost-effectiveness analysis of universal screening for carbapenemase-producing Enterobacteriaceae in hospital inpatients.

The purpose of this study was to assess the cost-effectiveness of screening all hospital inpatients for carbapenemase-producing Enterobacteriaceae (CPE) at the time of hospital admission, compared to not screening, from a US hospital perspective. We used a linked transmission/Markov model to compare outcomes for a typical hospitalized medical patient, from a community with a colonization prevalence of 0.05%. Outcomes were number of colonized patients, CPE-related clinical infections and deaths, expected quality-adjusted life years (QALYs), cost, and the incremental cost-effectiveness ratio (ICER). Sensitivity analyses were performed to assess the effect of parameter uncertainty, using a willingness-to-pay threshold of $100,000 per QALY gained. Screening prevented six CPE colonization cases per 1000 patients (1/1000 colonized with screening, 7/1000 without screening), over half of all symptomatic CPE infections (2/10,000 symptomatic with screening, 5/10,000 symptomatic without screening), and nearly half of all CPE-related deaths (8/100,000 deaths with screening, 15/100,000 deaths without screening). Screening accrued 0.0009 additional QALYs and cost an additional $24.68, compared to not screening, and was cost-effective (ICER $26,283 per QALY gained). Our results were sensitive to uncertainty in prevalence and the number of secondary colonizations per colonized patient. Screening was not cost-effective at a prevalence below 0.015% or if transmission to fewer than 0.9 new patients occurred for each colonized patient. At prevalence levels above 0.3%, screening was cost-saving compared to not screening. Screening inpatients for CPE carriage is likely cost-effective, and may be cost-saving, depending on the local prevalence of carriage.

Combined Phosphoramidite-Phosphodiester Reagents for the Synthesis of Methylene Bisphosphonates.

A new class of phosphanylmethylphosphonate reagents has been developed to enable the controlled synthesis of methylene bisphosphonate mono- and diesters. Condensation of such reagents with an alcohol of choice through azole-mediated phosphoramidite chemistry followed by in situ oxidation provides orthogonally protected methylene bisphosphonate tetraesters. Global deprotection of the tetraester leads to terminal methylene bisphosphonates. Alternatively, selective deprotection at the terminal phosphonate followed by a condensation between the acquired methylene bisphosphonate triester and a second alcohol leads to methylene bisphosphonates diesters.

Cerebrospinal fluid neurofilament light chain levels predict visual outcome after optic neuritis.

BACKGROUND: Optic neuritis is a good model for multiple sclerosis relapse, but currently no tests can accurately predict visual outcome. OBJECTIVE: The purpose of this study was to examine whether cerebrospinal fluid (CSF) biomarkers of tissue damage and remodelling (neurofilament light chain (NF-L), myelin basic protein, osteopontin and chitinase-3-like-1) predict visual outcome after optic neuritis. METHODS: We included 47 patients with optic neuritis as a first demyelinating episode. Patients underwent visual tests, optical coherence tomography (OCT), magnetic resonance imaging (MRI) and lumbar puncture. Biomarkers were measured in CSF by enzyme-linked immunosorbent assay (ELISA). Patients were followed up six months after onset and this included visual tests and OCT. Outcome measures were inter-ocular differences in low contrast visual acuity (LCVA), retinal nerve fibre layer (RNFL) and ganglion cell layer+inner plexiform layer (GC-IPL) thicknesses. RESULTS: CSF NF-L levels at onset predicted inter-ocular differences in follow-up LCVA (ß=13.8, p=0.0008), RNFL (ß=5.6, p=0.0004) and GC-IPL (ß=4.0, p=0.0008). The acute-phase GC-IPL thickness also predicted follow-up LCVA (ß=12.9, p=0.0021 for NF-L, ß=-1.1, p=0.0150 for GC-IPL). Complete/incomplete remission was determined based on LCVA from 30 healthy controls. NF-L had a positive predictive value of 91% and an area under the curve (AUC) of 0.79 for incomplete remission. CONCLUSION: CSF NF-L is a promising biomarker of visual outcome after optic neuritis. This could aid neuroprotective/regenerative medical advancements.

Discovery of small molecule CD40-TRAF6 inhibitors.

The CD154-CD40 receptor complex plays a pivotal role in several inflammatory pathways. Attempts to inhibit the formation of this complex have resulted in systemic side effects. Downstream inhibition of the CD40 signaling pathway therefore seems a better way to ameliorate inflammatory disease. To relay a signal, the CD40 receptor recruits adapter proteins called tumor necrosis factor receptor-associated factors (TRAFs). CD40-TRAF6 interactions are known to play an essential role in several inflammatory diseases. We used in silico, in vitro, and in vivo experiments to identify and characterize compounds that block CD40-TRAF6 interactions. We present in detail our drug docking and optimization pipeline and show how we used it to find lead compounds that reduce inflammation in models of peritonitis and sepsis. These compounds appear to be good leads for drug development, given the observed absence of side effects and their demonstrated efficacy for peritonitis and sepsis in mouse models.

The presence of mast cell clonality in patients with unexplained anaphylaxis.

BACKGROUND: The mechanisms by which mast cells in patients with unexplained anaphylaxis (UEA) are triggered remain elusive. Onset of episodes is unpredictable and often recurrent. The substantial overlap between the clinical manifestations of UEA and clonal mast cell disorders (CMD) suggests an association between these rare disorders. The two forms of CMD characterized to date are systemic mastocytosis (SM) and monoclonal mast cell activation syndrome (MMAS). OBJECTIVE: To examine the hypothesis that the pathogenesis of UEA reflects the presence of aberrant subpopulations of mast cells. METHODS: Thirty (14 men, 16 women) patients (≥ 18 years) suffering from UEA and with no signs of cutaneous mastocytosis were recruited. Patients underwent an initial complete allergy work-up to confirm the diagnosis of UEA. Level of baseline serum tryptase (sBT) and total IgE were determined. In addition, a bone marrow examination was performed on all 30 patients to investigate possible underlying CMD. RESULTS: Fourteen (47%) of our cases (nine men, five women) were diagnosed with CMD: 10 with SM and four with MMAS. Four of the 10 patients with SM had mast cell aggregates in their bone marrow. All patients with SM exhibited a sBT level > 11.4 ng/mL, whereas this level was elevated in only two of those with MMAS and four with UAE but not diagnosed with CMD. Total IgE levels were lower in the group of patients with CMD (P < 0.03). CONCLUSION AND CLINICAL RELEVANCE: The pathogenic mechanism underlying UEA could be explained by the presence of immunophenotypically aberrant mast cells with clonal markers in 47% of our subjects, indicating that clonal mast cell disorders are present in a substantial subset of these patients. Thus, the presence of CMD should be considered in patients with UEA if they have an elevated level of sBT (≥ 11.4 ng/mL) and cardiovascular symptoms such as syncope.

A complex V ATP5A1 defect causes fatal neonatal mitochondrial encephalopathy.

Whole exome sequencing is a powerful tool to detect novel pathogenic mutations in patients with suspected mitochondrial disease. However, the interpretation of novel genetic variants is not always straightforward. Here, we present two siblings with a severe neonatal encephalopathy caused by complex V deficiency. The aim of this study was to uncover the underlying genetic defect using the combination of enzymatic testing and whole exome sequence analysis, and to provide evidence for causality by functional follow-up. Measurement of the oxygen consumption rate and enzyme analysis in fibroblasts were performed. Immunoblotting techniques were applied to study complex V assembly. The coding regions of the genome were analysed. Three-dimensional modelling was applied. Exome sequencing of the two siblings with complex V deficiency revealed a heterozygous mutation in the ATP5A1 gene, coding for complex V subunit α. The father carried the variant heterozygously. At the messenger RNA level, only the mutated allele was expressed in the patients, whereas the father expressed both the wild-type and the mutant allele. Gene expression data indicate that the maternal allele is not expressed, which is supported by the observation that the ATP5A1 expression levels in the patients and their mother are reduced to ∼50%. Complementation with wild-type ATP5A1 restored complex V in the patient fibroblasts, confirming pathogenicity of the defect. At the protein level, the mutation results in a disturbed interaction of the α-subunit with the ß-subunit of complex V, which interferes with the stability of the complex. This study demonstrates the important value of functional studies in the diagnostic work-up of mitochondrial patients, in order to guide genetic variant prioritization, and to validate gene defects.

The intubation scoop (i-scoop) - a new type of laryngoscope for difficult and normal airways.

The i-scoop is an intubation device with a curved guiding bar with laterally located lenses at its tip, rather than a blade. Twenty-five anaesthesiologists intubated a manikin that simulated first a normal and then a difficult airway. All participants were able to intubate the difficult airway with a good view of the glottis using the i-scoop. None was able to intubate using seven other laryngoscopes (Macintosh laryngoscope, GlideScope(®) GVL and AVL, McGrath(®) (Series 5/MAC), C-MAC(®) , A.P. Advance(™) ). Intubation was successful only with the Airtraq(®) (n = 10), the Airway Scope (n = 5), the C-MAC D-Blade (n = 2), the A.P. Advance DAB (n = 1) and the GlideScope DL Trainer (n = 1) (p < 0.001, success rate of i-scoop vs all 12 laryngoscopes combined). In contrast to all other videolaryngoscopes, intubation of the normal airway with the i-scoop was achieved even faster than with the Macintosh laryngoscope (p < 0.02). The i-scoop outperformed all other laryngoscopes in both difficult and normal airways, and therefore has potential as an easier and safer alternative to present devices.

Is microvessel density correlated with anastomotic leakage after low anterior resection?

BACKGROUND/AIMS: Anastomotic leakage after low anterior resection may be the result of poor vascular supply from the proximal anastomotic loop. The purpose of this study was to investigate the correlation between colonic microvessel density and anastomotic breakdown. METHODOLOGY: Between 2006 and 2009, a consecutive series of 81 patients underwent double-stapled low anterior resection followed by a colorectal anastomosis. Symptomatic anastomotic leakage occurred in 14 patients (17%). In these patients, microvascular density was determined by image analysis of CD-31-immunostained sections from the proximal resection site. The results were compared with a sample of the remaining 67 patients without anastomotic leakage closely matched for age, gender, ASA-classification, pathological stage and neoadjuvant treatment. RESULTS: The mean percentage of anti-CD31 stained area, obtained from the proximal resection site was similar between patients with or without anastomotic leakage (4.0% +/- 1.8% versus 4.4% +/- 1.6% respectively, P = 0.53). With respect to neo-adjuvant therapy, no differences in the density of CD31 positive were observed (pre-operative radiotherapy = 4.3% +/- 1.8% versus pre-operative chemoradiotherapy 4.1% +/- 1.6%, P = 0.77). The mean vessel density reached borderline statistical significance in women (5.0% +/- 1.8%) compared to men (3.8% +/- 1.8%) (P = 0.06). CONCLUSIONS: Microvessel density quantification with immunohistochemical analysis of CD31 expression of the proximal anastomotic region did not show any correlation with anastomotic leakage in the clinical setting.

Impact of changes in metabolic control on progression to photocoagulation for clinically significant macular oedema: a 20 year study of type 1 diabetes.

AIMS/HYPOTHESIS: Although increasing hyperglycaemia, arterial hypertension and longer duration of diabetes raise the risk of progression of diabetic retinopathy, short-term benefits in terms of improved metabolic control and lowered blood pressure have not been demonstrated. We therefore examined the effect of changes in glycaemia and arterial blood pressure on the incidence of clinically significant macular oedema in a population of diabetic patients. METHODS: We performed a retrospective review of all patients with type 1 diabetes who attended the retinopathy screening clinic at the Steno Diabetes Center from 1988 to 2008, using the endpoint referral to first photocoagulation treatment for clinically significant diabetic macular oedema. The analysis included 1,878 patients (median observation, 8 years). Changes were defined as the inter-visit change; in the case of an event the last event-free interval before referral, where the median screening interval was 6 months. RESULTS: Risk of progression to photocoagulation for macular oedema increased with duration of diabetes (p < 0.001), current HbA1c (p < 0.0001) and with the magnitude of changes in HbA1c (p = 0.0002) and systolic blood pressure (p < 0.0001) in a multiple regression model. A recent decrease of ≥ 0.5 percentage points or an increase in HbA1c of >0.5 percentage points per 6 months was associated with HRs of 3.04 and 1.28, respectively, compared with lesser changes in HbA1c. CONCLUSIONS/INTERPRETATION: In this study, large recent changes in metabolic control and systolic blood pressure, irrespective of direction, were independent risk factors for progression to photocoagulation for diabetic macular oedema. The effects of metabolic and haemodynamic stability on diabetic retinopathy should be examined in prospective studies.

Evolution and diversification of the organellar release factor family.

Translation termination is accomplished by proteins of the Class I release factor family (RF) that recognize stop codons and catalyze the ribosomal release of the newly synthesized peptide. Bacteria have two canonical RFs: RF1 recognizes UAA and UAG, RF2 recognizes UAA and UGA. Despite that these two release factor proteins are sufficient for de facto translation termination, the eukaryotic organellar RF protein family, which has evolved from bacterial release factors, has expanded considerably, comprising multiple subfamilies, most of which have not been functionally characterized or formally classified. Here, we integrate multiple sources of information to analyze the remarkable differentiation of the RF family among organelles. We document the origin, phylogenetic distribution and sequence structure features of the mitochondrial and plastidial release factors: mtRF1a, mtRF1, mtRF2a, mtRF2b, mtRF2c, ICT1, C12orf65, pRF1, and pRF2, and review published relevant experimental data. The canonical release factors (mtRF1a, mtRF2a, pRF1, and pRF2) and ICT1 are derived from bacterial ancestors, whereas the others have resulted from gene duplications of another release factor. These new RF family members have all lost one or more specific motifs relevant for bona fide release factor function but are mostly targeted to the same organelle as their ancestor. We also characterize the subset of canonical release factor proteins that bear nonclassical PxT/SPF tripeptide motifs and provide a molecular-model-based rationale for their retained ability to recognize stop codons. Finally, we analyze the coevolution of canonical RFs with the organellar genetic code. Although the RF presence in an organelle and its stop codon usage tend to coevolve, we find three taxa that encode an RF2 without using UGA stop codons, and one reverse scenario, where mamiellales green algae use UGA stop codons in their mitochondria without having a mitochondrial type RF2. For the latter, we put forward a "stop-codon reinvention" hypothesis that involves the retargeting of the plastid release factor to the mitochondrion.

PRPS1 mutations: four distinct syndromes and potential treatment.

Phosphoribosylpyrophosphate synthetases (PRSs) catalyze the first step of nucleotide synthesis. Nucleotides are central to cell function, being the building blocks of nucleic acids and serving as cofactors in cellular signaling and metabolism. With this in mind, it is remarkable that mutations in phosphoribosylpyrophosphate synthetase 1 (PRPS1), which is the most ubiquitously expressed gene of the three PRS genes, are compatible with life. Mutations described thus far in PRPS1 are all missense mutations that result in PRS-I superactivity or in variable levels of decreased activity, resulting in X-linked Charcot-Marie-Tooth disease-5 (CMTX5), Arts syndrome, and X-linked nonsyndromic sensorineural deafness (DFN2). Patients with PRS-I superactivity primarily present with uric acid overproduction, mental retardation, ataxia, hypotonia, and hearing impairment. Postlingual progressive hearing loss is found as an isolated feature in DFN2 patients. Patients with CMTX5 and Arts syndrome have peripheral neuropathy, including hearing impairment and optic atrophy. However, patients with Arts syndrome are more severely affected because they also have central neuropathy and an impaired immune system. The neurological phenotype in all four PRPS1-related disorders seems to result primarily from reduced levels of GTP and possibly other purine nucleotides including ATP, suggesting that these disorders belong to the same disease spectrum. Preliminary results of S-adenosylmethionine (SAM) supplementation in two Arts syndrome patients show improvement of their condition, indicating that SAM supplementation in the diet could alleviate some of the symptoms of patients with PRPS1 spectrum diseases by replenishing purine nucleotides (J.C., unpublished data).