Lung adenocarcinomas without driver genes converge to common adaptive strategies through diverse genetic, epigenetic, and niche construction evolutionary pathways.

Somatic evolution selects cancer cell phenotypes that maximize survival and proliferation in dynamic environments. Although cancer cells are molecularly heterogeneous, we hypothesized convergent adaptive strategies to common host selection forces can be inferred from patterns of epigenetic and genetic evolutionary selection in similar tumors. We systematically investigated gene mutations and expression changes in lung adenocarcinomas with no common driver genes (n = 313). Although 13,461 genes were mutated in at least one sample, only 376 non-synonymous mutations evidenced positive evolutionary selection with conservation of 224 genes, while 1736 and 2430 genes exhibited ≥ two-fold increased and ≥ 50% decreased expression, respectively. Mutations under positive selection are more frequent in genes with significantly altered expression suggesting they often "hardwire" pre-existing epigenetically driven adaptations. Conserved genes averaged 16-fold higher expression in normal lung tissue compared to those with selected mutations demonstrating pathways necessary for both normal cell function and optimal cancer cell fitness. The convergent LUAD phenotype exhibits loss of differentiated functions and cell-cell interactions governing tissue organization. Conservation with increased expression is found in genes associated with cell cycle, DNA repair, p53 pathway, epigenetic modifiers, and glucose metabolism. No canonical driver gene pathways exhibit strong positive selection, but extensive down-regulation of membrane ion channels suggests decreased transmembrane potential may generate persistent proliferative signals. NCD LUADs perform niche construction generating a stiff, immunosuppressive microenvironment through selection of specific collagens and proteases. NCD LUADs evolve to a convergent phenotype through a network of interconnected genetic, epigenetic, and ecological pathways.

Experiences of consumers, carers and clinicians during borderline personality disorder presentations to the emergency department-An integrative review.

INTRODUCTION: People with a borderline personality disorder (BPD) diagnosis or symptoms may experience emotional crises which necessitate use of the emergency department (ED). No existing reviews focus specifically on experiences of consumersa, carersb and clinicians in relation to ED presentations by people diagnosed with BPD. AIM/QUESTION: The aim of this study was to synthesise knowledge on consumer, carer and clinician experiences of BPD in the ED. METHOD: An integrative review methodology was chosen as it best captures the complexity of varied perspectives and emergent phenomena from diverse literature sources. EMBASE, CINAHL, PsycInfo and Medline were searched for papers published before 16 February 2022. RESULTS: Nine papers met the inclusion criteria (five qualitative, one quantitative, one mixed methods and two letters to the editor). Key themes were barriers to timely and adequate care, and stigmatising attitudes and practices towards people diagnosed with BPD. Negative attitudes were perceived to perpetuate harmful outcomes and further ED visits. DISCUSSION: Predominantly negative ED experiences were expressed by clinicians, consumers and carers. Further work is needed in ED models of care and staff education to improve the experience of care for consumers, carers and clinicians alike. IMPLICATIONS FOR PRACTICE: Opportunities for change will exist through co-designed innovation, education, advocacy and leadership.

Telemonitoring With a Connected Glucose Meter Improves Glycemia Among People With Insulin-Treated Type 2 Diabetes.

BACKGROUND: Delayed initiation and inadequate titration remain critical challenges to optimizing insulin therapy in type 2 diabetes (T2D). We aimed to study whether hemoglobin A1c (HbA1c) can be lowered in people with insulin-treated T2D using telemonitoring. METHODS: This single-center study recruited adults with greater than or equal to six months of diabetes, greater than or equal to three months of insulin therapy, HbA1c ≥8.5% and ≤12.5%, and body mass index (BMI) ≤40 kg/m2. All participants received a connected glucose meter and the accompanying smartphone application. Participants sent weekly blood glucose (BG) diary to their primary endocrinologist via email. Adjustments in insulin doses were communicated to the participants. HbA1c, proportion of BG readings in range (70-180 mg/dL, PIR), below range (<70 mg/dL, PBR) and above range (>180 mg/dL, PAR), and glycemic variability as the coefficient of variation (% CV) were measured at baseline, week 12, and week 24 and compared using repeated-measures analysis of variance (ANOVA) or Friedman's ANOVA. RESULTS: We recruited 40 people (55% women). Mean age was 57.9 years, BMI 27.8 kg/m2, and baseline HbA1c 9.8% (83.7 mmol/mol). Mean HbA1c improved by 1.7%, % CV reduced from 32.9% to 30.7%, PIR increased from 58.8% to 67.1% (all P <.01) by week 24, without any change in PBR. This was achieved with a 0.04 U/kg/d median increase in total daily dose of insulin and 0.9 kg weight gain over 24 weeks. CONCLUSION: Telemonitoring and titration of insulin using a connected glucose meter resulted in significant improvements in glycemia, characterized by a reduction in HbA1c, increase in PIR, and reduction in glycemic variability without any increase in hypoglycemia.

Oral Peroxisome Proliferator-Activated Receptor-α Agonist Enhances Corneal Nerve Regeneration in Patients With Type 2 Diabetes.

Diabetic corneal neuropathy (DCN) is a common complication of diabetes. However, there are very limited therapeutic options. We investigated the effects of a peroxisome proliferator-activated receptor-α (PPAR-α) agonist, fenofibrate, on 30 patients (60 eyes) with type 2 diabetes. On in vivo confocal microscopy evaluation, there was significant stimulation of corneal nerve regeneration and a reduction in nerve edema after 30 days of oral fenofibrate treatment, as evidenced by significant improvement in corneal nerve fiber density (CNFD) and corneal nerve fiber width, respectively. Corneal epithelial cell morphology also significantly improved in cell circularity. Upon clinical examination, fenofibrate significantly improved patients' neuropathic ocular surface status by increasing tear breakup time along with a reduction of corneal and conjunctival punctate keratopathy. Tear substance P (SP) concentrations significantly increased after treatment, suggesting an amelioration of ocular surface neuroinflammation. The changes in tear SP concentrations was also significantly associated with improvement in CNFD. Quantitative proteomic analysis demonstrated that fenofibrate significantly upregulated and modulated the neurotrophin signaling pathway and linolenic acid, cholesterol, and fat metabolism. Complement cascades, neutrophil reactions, and platelet activation were also significantly suppressed. Our results showed that fenofibrate could potentially be a novel treatment for patients with DCN.

Baseline characteristics of participants in the Pre-Diabetes Interventions and Continued Tracking to Ease-out Diabetes (Pre-DICTED) Program.

OBJECTIVE: The Pre-Diabetes Interventions and Continued Tracking to Ease-out Diabetes (Pre-DICTED) Program is a diabetes prevention trial comparing the diabetes conversion rate at 3 years between the intervention group, which receives the incentivized lifestyle intervention program with stepwise addition of metformin, and the control group, which receives the standard of care. We describe the baseline characteristics and compare Pre-DICTED participants with other diabetes prevention trials cohort. RESEARCH DESIGN AND METHODS: Participants were aged between 21 and 64 years, overweight (body mass index (BMI) ≥23.0 kg/m2), and had pre-diabetes (impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT)). RESULTS: A total of 751 participants (53.1% women) were randomized. At baseline, mean (SD) age was 52.5 (8.5) years and mean BMI (SD) was 29.0 (4.6) kg/m2. Twenty-three per cent had both IFG and IGT, 63.9% had isolated IGT, and 13.3% had isolated IFG. Ethnic Asian Indian participants were more likely to report a family history of diabetes and had a higher waist circumference, compared with Chinese and Malay participants. Women were less likely than men to meet the physical activity recommendations (≥150 min of moderate-intensity physical activity per week), and dietary intake varied with both sex and ethnicity. Compared with other Asian diabetes prevention studies, the Pre-DICTED cohort had a higher mean age and BMI. CONCLUSION: The Pre-DICTED cohort represents subjects at high risk of diabetes conversion. The study will evaluate the effectiveness of a community-based incentivized lifestyle intervention program in an urban Asian context.

Bi-allelic LETM1 variants perturb mitochondrial ion homeostasis leading to a clinical spectrum with predominant nervous system involvement.

Leucine zipper-EF-hand containing transmembrane protein 1 (LETM1) encodes an inner mitochondrial membrane protein with an osmoregulatory function controlling mitochondrial volume and ion homeostasis. The putative association of LETM1 with a human disease was initially suggested in Wolf-Hirschhorn syndrome, a disorder that results from de novo monoallelic deletion of chromosome 4p16.3, a region encompassing LETM1. Utilizing exome sequencing and international gene-matching efforts, we have identified 18 affected individuals from 11 unrelated families harboring ultra-rare bi-allelic missense and loss-of-function LETM1 variants and clinical presentations highly suggestive of mitochondrial disease. These manifested as a spectrum of predominantly infantile-onset (14/18, 78%) and variably progressive neurological, metabolic, and dysmorphic symptoms, plus multiple organ dysfunction associated with neurodegeneration. The common features included respiratory chain complex deficiencies (100%), global developmental delay (94%), optic atrophy (83%), sensorineural hearing loss (78%), and cerebellar ataxia (78%) followed by epilepsy (67%), spasticity (53%), and myopathy (50%). Other features included bilateral cataracts (42%), cardiomyopathy (36%), and diabetes (27%). To better understand the pathogenic mechanism of the identified LETM1 variants, we performed biochemical and morphological studies on mitochondrial K+/H+ exchange activity, proteins, and shape in proband-derived fibroblasts and muscles and in Saccharomyces cerevisiae, which is an important model organism for mitochondrial osmotic regulation. Our results demonstrate that bi-allelic LETM1 variants are associated with defective mitochondrial K+ efflux, swollen mitochondrial matrix structures, and loss of important mitochondrial oxidative phosphorylation protein components, thus highlighting the implication of perturbed mitochondrial osmoregulation caused by LETM1 variants in neurological and mitochondrial pathologies.

COVID-19 pandemic unmasking cardiovascular risk factors and non-communicable diseases among migrant workers: a cross-sectional study in Singapore.

OBJECTIVES: This study aims to report the prevalence of cardiovascular risk factors (CVRFs) and other non-communicable diseases among migrant workers in Singapore admitted for COVID-19 infection, to highlight disease burden and the need for changes in health screening and healthcare delivery in this unique population. SETTING: The study was conducted in the largest tertiary hospital in Singapore. DESIGN: Retrospective cross-sectional study. PARTICIPANTS: 883 migrant workers who had mild or asymptomatic COVID-19 infection admitted to three isolation wards between 6 April 2020 and 31 May 2020 were included in this study. OUTCOME MEASURES: The outcome measures were the prevalence of pre-existing and newly diagnosed comorbid conditions and the prevalence of CVRFs-diabetes mellitus, hypertension and hyperlipidaemia-and non-communicable diseases at the time of discharge. The OR of having specific CVRFs depending on country of origin was generated via multivariate logistic regression analysis. RESULTS: The median age of our study population was 45 years. 17.0% had pre-existing conditions and 25.9% received new diagnoses. Of the new diagnoses, 15.7% were acute medical conditions and 84.3% chronic medical conditions. The prevalence of CVRFs was higher in Southeast Asian and South Asian migrant workers compared with Chinese. The prevalence of non-communicable diseases on discharge was highest among Southeast Asians (49.4%). CONCLUSIONS: The COVID-19 outbreak in a large number of migrant workers in Singapore unmasked a significant disease burden among them, increasing stakeholders' interests in their welfare. Moving forward, system-level changes are necessary to deliver healthcare sustainably and effect improvements in migrant workers' health.

Pathogenic SLC25A26 variants impair SAH transport activity causing mitochondrial disease.

The SLC25A26 gene encodes a mitochondrial inner membrane carrier that transports S-adenosylmethionine (SAM) into the mitochondrial matrix in exchange for S-adenosylhomocysteine (SAH). SAM is the predominant methyl-group donor for most cellular methylation processes, of which SAH is produced as a by-product. Pathogenic, biallelic SLC25A26 variants are a recognized cause of mitochondrial disease in children, with a severe neonatal onset caused by decreased SAM transport activity. Here, we describe two, unrelated adult cases, one of whom presented with recurrent episodes of severe abdominal pain and metabolic decompensation with lactic acidosis. Both patients had exercise intolerance and mitochondrial myopathy associated with biallelic variants in SLC25A26, which led to marked respiratory chain deficiencies and mitochondrial histopathological abnormalities in skeletal muscle that are comparable to those previously described in early-onset cases. We demonstrate using both mouse and fruit fly models that impairment of SAH, rather than SAM, transport across the mitochondrial membrane is likely the cause of this milder, late-onset phenotype. Our findings associate a novel pathomechanism with a known disease-causing protein and highlight the quests of precision medicine in optimizing diagnosis, therapeutic intervention and prognosis.

Non-steroidal anti-inflammatory drugs and risk of acute adverse renal outcomes in diabetes and diabetic kidney disease.

BACKGROUND: Individuals with diabetes mellitus (DM) may be susceptible to non-steroidal anti-inflammatory drug (NSAID)-induced acute kidney injury (AKI) but data on NSAID-related adverse renal events is sparse. OBJECTIVE: We aimed to evaluate the risk of acute kidney injury and/or hyperkalemia after systemic NSAID among individuals with DM and diabetic chronic kidney disease (CKD). METHODS: Retrospective cohort study of 3896 adults with DM with incident prescriptions between July 2015 and December 2017 from Singapore General Hospital and SingHealth Polyclinics. Laboratory, hospitalization and medication data were retrieved from electronic medical records. The primary outcome was the incidence of AKI and/ or hyperkalemia within 30 days after prescription. RESULTS: AKI and/or hyperkalemia occurred in 13.5% of all DM and 15.8% of diabetic CKD. The association between systemic NSAID >14 days and 30-day risk of AKI and/or hyperkalemia failed to reach statistical significance in unselected DM (adjusted OR 1.62, 95% CI 0.99-2.65, p = 0.05) and diabetic CKD (adjusted OR 0.64, 95% CI 0.15-2.82, p = 0.64), but the odds of AKI and/or hyperkalemia were markedly and significantly increased when NSAID was prescribed with renin-angiotensin-aldosterone system (RAAS) blocker (adjusted OR 4.17, 95% CI 1.74-9.98, p = 0.001) or diuretic (adjusted OR 3.31, 95% CI 1.09-10.08, p = 0.04) and in the absence of diabetic CKD (adjusted OR 1.98, 95% CI 1.16-3.36, p = 0.01). CONCLUSION: NSAID prescription >14 days in individuals with DM with concurrent RAAS blockers or diuretics was associated with higher 30-day risk of AKI and/or hyperkalemia.

Satisfaction of patients with diabetic kidney disease with traditional chinese medicine physician visits.

Background: Patient-centred care is an important part of quality healthcare and patient satisfaction has been shown to be associated with improved clinical outcomes. We aim to explore the satisfaction of patients with diabetic kidney disease (DKD) with their visits to the TCM physician and its association with patients' socio-economic characteristics. Methods: A questionnaire survey was conducted among patients aged >21 years with DKD. Participants' demographic, socioeconomic characteristics and satisfaction scores measured with the self-administered Medical Interview Satisfaction Scale (MISS) were collected after they visited the TCM physician. MISS is a 26-item questionnaire consisting of three domains - cognitive, affective and behavioural which was developed to assess patient satisfaction with medical consultation. Independent samples t-test and one-way analysis of variance (ANOVA) were used to analyse the data. Results: 137 participants completed the questionnaires and were included in the analysis. The mean satisfaction score was 3.1 out of 5, with the cognitive domain being significantly higher compared to the affective and behavioural domains. The mean satisfaction score of the cognitive domain differed significantly among participants staying in different types of housing and those with previous TCM encounters. The mean satisfaction score of the behavioural domain differed significantly among participants of different ethnicities. The mean satisfaction scores of all the domains were also significantly different among participants with different duration of follow-up with their TCM physicians. Conclusion: We found that ethnicity, types of housing, previous TCM experience and the duration of follow-up with the TCM physician may affect the satisfaction scores of patients with DKD.

Trends in cardiovascular risk factors and treatment goals in patients with diabetes in Singapore-analysis of the SingHealth Diabetes Registry.

BACKGROUND: Asian populations are at high risk of diabetes and related vascular complications. We examined risk factor control, preventive care, and disparities in these trends among adults with diabetes in Singapore. METHODS: The sample included 209,930 adults with diabetes aged≥18 years from a multi-institutional SingHealth Diabetes Registry between 2013 and 2019 in Singapore. We performed logistic generalized estimating equations (GEEs) regression analysis and used linear mixed effect modeling to evaluate the temporal trends. RESULTS: Between 2013 and 2019, the unadjusted control rates of glycated hemoglobin (4.8%, 95%CI (4.4 to 5.1) and low-density lipoprotein cholesterol (LDL-C) (11.5%, 95%CI (11.1 to 11.8)) improved, but blood pressure (BP) control worsened (systolic BP (SBP)/diastolic BP (DBP) <140/90 mmHg: -6.6%, 95%CI (-7.0 to -6.2)). These trends persisted after accounting for the demographics including age, gender, ethnicity, and housing type. The 10-year adjusted risk for coronary heart disease (CHD) (3.4%, 95% (3.3 to 3.5)) and stroke (10.4%, 95% CI (10.3 to 10.5)) increased. In 2019, the control rates of glycated hemoglobin, BP (SBP/DBP<140/90 mmHg), LDL-C, each, and all three risk factors together, accounted for 51.5%, 67.7%, 72.2%, and 24.4%, respectively. CONCLUSIONS: Trends in risk factor control improved for glycated hemoglobin and LDL-C, but worsened for BP among diabetic adults in Singapore from 2013 to 2019. Control rates for all risk factors remain inadequate.

The Pre-Diabetes Interventions and Continued Tracking to Ease-out Diabetes (Pre-DICTED) program: study protocol for a randomized controlled trial.

BACKGROUND: Community-based diabetes prevention programs varied widely in effectiveness, and the intervention strategy consisting of lifestyle interventions, stepwise addition of metformin, and financial incentives has not been studied in real-world clinical practice settings. The Pre-Diabetes Interventions and Continued Tracking to Ease-out Diabetes (Pre-DICTED) trial is a pragmatic trial that aims to compare the effectiveness of a community-based stepwise diabetes prevention program with added financial incentives (intervention) versus the standard of care (control) in reducing the risk of type 2 diabetes over 3 years among overweight or obese individuals with pre-diabetes. METHODS: This is an open-label, 1:1 randomized controlled trial which aims to recruit 846 adult individuals with isolated impaired fasting glucose (IFG), isolated impaired glucose tolerance (IGT), or both IFG and IGT from Singapore. Intervention arm participants attend 12 group-based sessions (2 nutrition workshops, 9 exercise sessions, and a goal-setting workshop) delivered at community sites (weeks 1 to 6), receive weekly physical activity and nutrition recommendations delivered by printed worksheets (weeks 7 to 12), and receive monthly health tips delivered by text messages (months 4 to 36). From month 6 onwards, intervention arm participants who remain at the highest risk of conversion to diabetes are prescribed metformin. Intervention arm participants are also eligible for a payment/rewards program with incentives tied to attendance at the group sessions and achievement of the weight loss target (5% of baseline weight). All participants are assessed at baseline, month 3, month 6, and every 6 months subsequently till month 36. The primary endpoint is the proportion of participants with diabetes at 3 years. Secondary endpoints include the mean change from baseline at 3 years in fasting plasma glucose, 2-hour plasma glucose, HbA1c, body weight, body mass index, physical activity, and dietary intake. DISCUSSION: The Pre-DICTED trial will provide evidence of the effectiveness and feasibility of a community-based stepwise diabetes prevention program with added financial incentives for individuals with pre-diabetes in Singapore. The study will provide data for a future cost-effectiveness analysis, which will be used to inform policymakers of the value of a nationwide implementation of the diabetes prevention program. TRIAL REGISTRATION: ClinicalTrials.gov NCT03503942 . Retrospectively registered on April 20, 2018. Protocol version: 5.0 Date: 1 March 2019.

Diagnosing Mitochondrial Disorders Remains Challenging in the Omics Era.

OBJECTIVE: We hypothesized that novel investigative pathways are needed to decrease diagnostic odysseys in pediatric mitochondrial disease and sought to determine the utility of clinical exome sequencing in a large cohort with suspected mitochondrial disease and to explore whether any of the traditional indicators of mitochondrial disease predict a confirmed genetic diagnosis. METHODS: We investigated a cohort of 85 pediatric patients using clinical exome sequencing and compared the results with the outcome of traditional diagnostic tests, including biochemical testing of routine parameters (lactate, alanine, and proline), neuroimaging, and muscle biopsy with histology and respiratory chain enzyme activity studies. RESULTS: We established a genetic diagnosis in 36.5% of the cohort and report 20 novel disease-causing variants (1 mitochondrial DNA). Counterintuitively, routine biochemical markers were more predictive of mitochondrial disease than more invasive and elaborate muscle studies. CONCLUSIONS: We propose using biochemical markers to support the clinical suspicion of mitochondrial disease and then apply first-line clinical exome sequencing to identify a definite diagnosis. Muscle biopsy studies should only be used in clinically urgent situations or to confirm an inconclusive genetic result. CLASSIFICATION OF EVIDENCE: This is a Class II diagnostic accuracy study showing that the combination of CSF and plasma biochemical tests plus neuroimaging could predict the presence or absence of exome sequencing confirmed mitochondrial disorders.

Empower to connect and connect to empower: experience in using a humanistic approach to improve patients' access to, and experience of, care in isolation wards during the COVID-19 outbreak in Singapore.

Patients admitted to the isolation ward during the COVID-19 outbreak face multiple psychosocial stressors including the disruptive experience of being in quarantine, anxiety over contracting a newly emerging infectious disease and limited access to their healthcare team. This quality improvement project aims to leverage on technology to improve patients' access to, and experience of, care while in isolation.Patients admitted to two isolation wards in Singapore General Hospital (SGH) between 28 February and 19 March 2020 were each provided an iPad loaded with the MyCare application (app), curated materials and mobile games. During this period, 83 of them accessed the device and the app. MyCare app is an app developed by the nursing team in SGH as part of an existing interprofessional collaboration to help patients navigate their care during their inpatient stay. In response to COVID-19, MyCare app was supplemented with materials to address affected patients' informational and psychosocial needs. These materials included an information sheet on COVID-19, interviews with previous severe acute respiratory syndrome survivors, psychosocial support materials, and uplifting literature, illustrated storybooks and artwork.This paper describes the process of planning for, and executing, the intervention and reports the initial results of its effect. Initial feedback indicated a positive response to the intervention. 9 out of 10 respondents (90%) rated their hospital experience with a maximum of five stars and all 10 respondents (100%) rated the psychosocial support materials with five stars. Doctors managing the patients also observed a reduction in the number of commonly asked questions following the deployment of the iPad.This quality improvement project is ongoing with plans for further research to determine how to better support the psychosocial needs of patients in isolation during a novel disease outbreak. This report is written based on the Standards for Quality Improvement Reporting Excellence guidelines.

Patient Preferences for Medications in Managing Type 2 Diabetes Mellitus: A Discrete Choice Experiment.

OBJECTIVES: To quantify patients' maximum acceptable risk (MAR) of urinary and genital tract infections (UGTI) in exchange for benefits associated with treatments for managing type 2 diabetes mellitus (T2DM). METHODS: In a discrete choice experiment, adult patients with T2DM and currently on metformin and/or sulphonylurea (first-line treatments) were asked to choose between 2 hypothetical medications defined by 6 attributes: years of medication effectiveness in controlling blood glucose, weight reduction, UGTI risk, risk of hospitalization from heart failure, all-cause mortality risk, and out-of-pocket medication cost. We used latent class logistic regression parameters to estimate the conditional relative importance of treatment attributes and MAR of UGTI for various treatment benefits. RESULTS: A 2-class latent class model was identified as the best fit for the responses from 147 patients. The first class (49% of sample), termed as "survival-conscious," stated that they were willing to accept 46% (95% confidence interval [CI]: 2%-90%) UGTI risk in exchange for a reduction from 6% to 1% in all-cause mortality risk. The second class (51% of sample), termed as "UGTI/cost-conscious" were willing to accept significantly lower (6%; CI: 2%-11%, and 5%; CI: 2%-8%) UGTI risk in exchange for the same reduction in all-cause mortality and hospitalization risks, respectively. CONCLUSIONS: On average, patients were willing to trade higher UGTI risk for a more effective medication. Our findings suggest that physicians should present the benefits and potential side effects of all available treatments and consider patient preferences in their treatment recommendations.

Expression of mutant exon 1 huntingtin fragments in human neural stem cells and neurons causes inclusion formation and mitochondrial dysfunction.

Robust cellular models are key in determining pathological mechanisms that lead to neurotoxicity in Huntington's disease (HD) and for high throughput pre-clinical screening of potential therapeutic compounds. Such models exist but mostly comprise non-human or non-neuronal cells that may not recapitulate the correct biochemical milieu involved in pathology. We have developed a new human neuronal cell model of HD, using neural stem cells (ReNcell VM NSCs) stably transduced to express exon 1 huntingtin (HTT) fragments with variable length polyglutamine (polyQ) tracts. Using a system with matched expression levels of exon 1 HTT fragments, we investigated the effect of increasing polyQ repeat length on HTT inclusion formation, location, neuronal survival, and mitochondrial function with a view to creating an in vitro screening platform for therapeutic screening. We found that expression of exon 1 HTT fragments with longer polyQ tracts led to the formation of intra-nuclear inclusions in a polyQ length-dependent manner during neurogenesis. There was no overt effect on neuronal viability, but defects of mitochondrial function were found in the pathogenic lines. Thus, we have a human neuronal cell model of HD that may recapitulate some of the earliest stages of HD pathogenesis, namely inclusion formation and mitochondrial dysfunction.

Expanding the molecular and phenotypic spectrum of truncating MT-ATP6 mutations.

OBJECTIVE: To describe the clinical and functional consequences of 1 novel and 1 previously reported truncating MT-ATP6 mutation. METHODS: Three unrelated probands with mitochondrial encephalomyopathy harboring truncating MT-ATP6 mutations are reported. Transmitochondrial cybrid cell studies were used to confirm pathogenicity of 1 novel variant, and the effects of all 3 mutations on ATPase 6 and complex V structure and function were investigated. RESULTS: Patient 1 presented with adult-onset cerebellar ataxia, chronic kidney disease, and diabetes, whereas patient 2 had myoclonic epilepsy and cerebellar ataxia; both harbored the novel m.8782G>A; p.(Gly86*) mutation. Patient 3 exhibited cognitive decline, with posterior white matter abnormalities on brain MRI, and severely impaired renal function requiring transplantation. The m.8618dup; p.(Thr33Hisfs*32) mutation, previously associated with neurogenic muscle weakness, ataxia, and retinitis pigmentosa, was identified. All 3 probands demonstrated a broad range of heteroplasmy across different tissue types. Blue-native gel electrophoresis of cultured fibroblasts and skeletal muscle tissue confirmed multiple bands, suggestive of impaired complex V assembly. Microscale oxygraphy showed reduced basal respiration and adenosine triphosphate synthesis, while reactive oxygen species generation was increased. Transmitochondrial cybrid cell lines studies confirmed the deleterious effects of the novel m.8782 G>A; p.(Gly86*) mutation. CONCLUSIONS: We expand the clinical and molecular spectrum of MT-ATP6-related mitochondrial disorders to include leukodystrophy, renal disease, and myoclonic epilepsy with cerebellar ataxia. Truncating MT-ATP6 mutations may exhibit highly variable mutant levels across different tissue types, an important consideration during genetic counseling.

The natural history of infantile mitochondrial DNA depletion syndrome due to RRM2B deficiency.

PURPOSE: Mitochondrial DNA (mtDNA) depletion syndrome (MDDS) encompasses a group of genetic disorders of mtDNA maintenance. Mutation of RRM2B is an uncommon cause of infantile-onset encephalomyopathic MDDS. Here we describe the natural history of this disease. METHODS: Multinational series of new genetically confirmed cases from six pediatric centers. RESULTS: Nine new cases of infantile-onset RRM2B deficiency, and 22 previously published cases comprised a total cohort of 31 patients. Infants presented at a mean of 1.95 months with truncal hypotonia, generalized weakness, and faltering growth. Seizures evolved in 39% at a mean of 3.1 months. Non-neurological manifestations included respiratory distress/failure (58%), renal tubulopathy (55%), sensorineural hearing loss (36%), gastrointestinal disturbance (32%), eye abnormalities (13%), and anemia (13%). Laboratory features included elevated lactate (blood, cerebrospinal fluid (CSF), urine, magnetic resonance (MR), spectroscopy), ragged-red and cytochrome c oxidase-deficient fibers, lipid myopathy, and multiple oxidative phosphorylation enzyme deficiencies in skeletal muscle. Eight new RRM2B variants were identified. Patients with biallelic truncating variants had the worst survival. Overall survival was 29% at 6 months and 16% at 1 year. CONCLUSIONS: Infantile-onset MDDS due to RRM2B deficiency is a severe disorder with characteristic clinical features and extremely poor prognosis. Presently management is supportive as there is no effective treatment. Novel treatments are urgently needed.