Further insights into Allan-Herndon-Dudley syndrome: characterization of two genetic variants in SLC16A2 gene

Genetics variants in SLC16A2 gene encoding for the monocarboxylate transporter 8 (MCT8) cause a severe X-linked intellectual deficit and neurological impairment known as Allan-Herndon-Dudley syndrome (AHDS). MCT8 promotes cellular uptake and efflux of thyroid hormone and its mutations provoke elevated serum T3 levels in children. Iodothyronine deiodinases (DIO) 1 and 2 are implicated in the conversion of T4 into biologically active T3, while DIO3 converts T4 into the inactive hormone reverse T3 (rT3). Active T3 and retinoid X receptors (RXR) can form heterodimer complexes which bind to hormone response elements (HREs) that leads to activate or repress transcription. Our aim is to investigate the impact of MCT8 mutations on the pathogenetic mechanisms of AHDS. Fibroblasts were obtained from skin biopsies of 2 AHDS and matched controls. To evaluate both MCT8 and thyroid hormone signaling pathway related genes expression, RNA was extracted with TRIzoLTM and assessed by Real-Time PCR. Protein expression was valuated via western blot and immunofluorescence. MTT assay was used to compare cell viability. Live and dead assay was used to discriminate live and dead populations. Lipids were detected via oil red o staining. MTT assay demonstrated a reduced cell viability as consequence of mutations in SLC16A2. We report that SLC16A2 RNA expression in AHDS patients was extremely reduced in comparison with total RNA from healthy controls. Additionally, DIO2, progastricsin, HR and KLF9 RNA expression resulted upregulated, whilst DIO1, DIO2-AS1, DIO3 and TH were downregulated influencing T3 cell entrance. Myelin related genes were significatively reduced. The lipid staining revealed an increasing presence of lipid droplets in AHDS patients. Taken together, our preliminary data emphasize an impairment in AHDS fibroblasts in relation to mutations in MCT8 transporter, increasing our understanding in the pathogenic mechanism of mutation in two patients affected by AHDS

Assessment of Type I Interferon Signaling in Pediatric Inflammatory Disease

International audiencePURPOSE: Increased type I interferon is considered relevant to the pathology of a number of monogenic and complex disorders spanning pediatric rheumatology, neurology, and dermatology. However, no test exists in routine clinical practice to identify enhanced interferon signaling, thus limiting the ability to diagnose and monitor treatment of these diseases. Here, we set out to investigate the use of an assay measuring the expression of a panel of interferon-stimulated genes (ISGs) in children affected by a range of inflammatory diseases. DESIGN, SETTING, AND PARTICIPANTS: A cohort study was conducted between 2011 and 2016 at the University of Manchester, UK, and the Institut Imagine, Paris, France. RNA PAXgene blood samples and clinical data were collected from controls and symptomatic patients with a genetically confirmed or clinically well-defined inflammatory phenotype. The expression of six ISGs was measured by quantitative polymerase chain reaction, and the median fold change was used to calculate an interferon score (IS) for each subject compared to a previously derived panel of 29 controls (where +2 SD of the control data, an IS of \textgreater2.466, is considered as abnormal). Results were correlated with genetic and clinical data. RESULTS: Nine hundred ninety-two samples were analyzed from 630 individuals comprising symptomatic patients across 24 inflammatory genotypes/phenotypes, unaffected heterozygous carriers, and controls. A consistent upregulation of ISG expression was seen in 13 monogenic conditions (455 samples, 265 patients; median IS 10.73, interquartile range (IQR) 5.90-18.41), juvenile systemic lupus erythematosus (78 samples, 55 patients; median IS 10.60, IQR 3.99-17.27), and juvenile dermatomyositis (101 samples, 59 patients; median IS 9.02, IQR 2.51-21.73) compared to controls (78 samples, 65 subjects; median IS 0.688, IQR 0.427-1.196), heterozygous mutation carriers (89 samples, 76 subjects; median IS 0.862, IQR 0.493-1.942), and individuals with non-molecularly defined autoinflammation (89 samples, 69 patients; median IS 1.07, IQR 0.491-3.74). CONCLUSIONS AND RELEVANCE: An assessment of six ISGs can be used to define a spectrum of inflammatory diseases related to enhanced type I interferon signaling. If future studies demonstrate that the IS is a reactive biomarker, this measure may prove useful both in the diagnosis and the assessment of treatment efficacy

More Than Hypomyelination in Pol-III Disorder

The 4H syndrome (hypomyelination, hypodontia, hypogonadotropic hypogonadism) is a newly recognized leukodystrophy. The classical form is characterized by the association of hypomyelination, abnormal dentition, and hypogonadotropic hypogonadism, but the recent identification of 2 genes responsible for the syndrome demonstrates that these 3 main characteristics can be variably combined among "Pol-III (polymerase III) Yrelated leukodystrophies.'' The pathophysiology of this group of diseases is still to be elucidated, and there are no neuropathologic descriptions of brain tissue. We report the clinical, neuroradiologic, and neuropathologic findings of a patient affected by 4H syndrome with confirmed POLR3A mutations. We found a marked loss of oligodendrocytes, varying in severity in different brain regions, and accompanied by severe loss of myelin, moderately severe loss of axons, and patchy perivascular regions of better preserved white matter. There was relatively mild white matter astrogliosis and microgliosis. A macrophage reaction involving viable normal-appearing oligodendroglia suggests the possibility of an immunologic process in this disorder. Cortical laminar astrogliosis and mineralization of Layers I and II in particular were present. Thus, despite the uniformly hypomyelinating pattern seen on magnetic resonance imaging, neuropathologic examination reveals a complex heterogeneous leukodystrophy with prominent neuroaxonal and glial involvement in this disorder

Further insights into Allan-Herndon-Dudley syndrome: a novel SLC16A2 splice site variant

Background Genetics variants in SLC16A2 gene encoding for the monocarboxylate transporter 8 (MCT8) cause a severe X-linked leukoencephalopathy known as Allan-Herndon-Dudley syndrome (AHDS). MCT8 promotes cellular uptake and efflux of thyroid hormone. Iodothyronine deiodinases (DIO) 1 and 2 are implicated in the conversion of T4 into biologically active T3, while DIO3 converts T4 into the inactive hormone reverse T3 (rT3). Active T3 and retinoid X receptors (RXR) can form heterodimer complexes which bind to hormone response elements (HREs) that leads to activate or repress transcription. Aim of the study The aim of this work is to investigate the impact of a novel SLC16A2 splice site variant on the pathogenesis of AHDS. Materials and Methods In silico prediction tools, such as Mutation Taster, were used to assess the pathogenic score of the identified variant, while splicing prediction tools, such as Fruit Fly Splice Predictor, were used to analyze the effect of variant on the splicing mechanism. Fibroblasts were obtained from skin biopsies of both AHDS patient and a matched control. To evaluate MCT8 and thyroid hormone signaling pathway related genes expression, RNA was extracted with TRIzoLTM and assessed by Real-Time PCR. Protein expression was evaluated via western blot and immunofluorescence. MTT assay was used to compare cell viability. Live and dead assay was used to discriminate live and dead populations. Lipid droplets were detected via oil red o staining. Results The identified variant in the SLC16A2 gene causes the breakup of the wild type donor splice site, possibly leading to exon 1 skipping, affecting cell viability. SLC16A2 RNA expression in our AHDS patient was extremely reduced in comparison with total RNA from healthy control. DIO2, progastricsin, HR and KLF9 RNA expression resulted upregulated, whilst DIO1, DIO2-AS1, DIO3 and TH were downregulated influencing T3 cell entrance. Myelin related genes were significatively reduced. The lipid staining revealed an increasing presence of lipid droplets in AHDS patients. Conclusions Our preliminary data emphasize an impairment in AHDS fibroblasts in relation to SLC16A2 splice site variant, increasing our understanding in the pathogenic mechanism of patients affected by AHDS

Time-course of myelination and atrophy on cerebral imaging in 35 patients with PLP1-related disorders

AIM Brain magnetic resonance imaging (MRI) motor development score (MDS) correlations were used to analyze the natural time-course of hypomyelinating PLP1-related disorders (Pelizaeus-Merzbacher disease [PMD] and spastic paraplegia type 2). METHOD Thirty-five male patients (ranging from 0.7-43.5y at the first MRI) with PLP1-related disorder were prospectively followed over 7 years. Patients were classified according to best motor function acquired before 5 years (MDS) into five categories (from PMD0 without motor acquisition to PMD4 with autonomous walking). We determined myelination and atrophy scores and measured corpus callosum area, volume of cerebellum, white matter and grey matter on 63 MRI. RESULTS Age-adjusted multivariate analysis revealed that patients with PMD0-1 had higher-severity atrophy scores and smaller corpus callosum area than did patients with PMD2 and PMD3-4. Myelination score increased until 12 years. There was evidence that the mean myelination differed in frontal white matter, arcuate fibres, and internal capsules among the groups. Most patients showed worsening atrophy (brain, cerebellum, corpus callosum), whereas grey matter and white matter proportions did not change. INTERPRETATION Brain atrophy and myelination of anterior cerebral regions appear to be pertinent biomarkers of motor development. The time-course of inter-and intra-individual cerebral white matter and grey matter atrophy suggests that both oligodendrocytes and neurons are involved in the physiopathology of PLP1-related disorders

New spastic paraplegia phenotype associated to mutation of NFU1

Recently an early onset lethal encephalopathy has been described in relation to mutations of NFU1, one of the genes involved in iron-sulfur cluster metabolism. We report a new NFU1 mutated patient presenting with a milder phenotype characterized by a later onset, a slowly progressive spastic paraparesis with relapsing-remitting episodes, mild cognitive impairment and a long survival. The early white matter abnormalities observed on MRI was combined with a mixed sensory-motor neuropathy in the third decade. Our case clearly suggests the importance of considering NFU1 mutation in slowly evolving leukoencephalopathy with high glycine concentration

Mucopolysaccharidosis-Plus Syndrome, a Rapidly Progressive Disease: Favorable Impact of a Very Prolonged Steroid Treatment on the Clinical Course in a Child

Mucopolysaccharidosis-plus syndrome (MPS-PS) is a novel autosomal recessive disorder caused by a mutation in the VPS33A gene. This syndrome presents with typical symptoms of mucopolysaccharidosis, as well as congenital heart defects, renal, and hematopoietic system disorders. To date, twenty-four patients have been described. There is no specific therapy for MPS-PS; clinical management is therefore limited to symptoms management. The clinical course is rapidly progressive, and most patients die before 1–2 years of age. We describe a currently 6-year-old male patient with MPS-PS presenting with multiorgan involvement. Symptoms started at four months of age when he progressively suffered from numerous acute and potentially life-threatening events. When he was two years old, he developed secondary hemophagocytic lymphohistiocytosis (HLH), which was successfully treated with steroids. To date, this child represents the oldest patient affected by MPS-PS described in the literature and the first one presenting with a life-threatening secondary HLH. The prolonged steroid treatment allowed a stabilization of his general and hematological conditions and probably determined an improvement of his psychomotor milestones and new neurological acquisitions with an improvement of quality of life. HLH should be suspected and adequately treated in MPS-PS patients presenting with suggestive symptoms of the disease. The usefulness of a prolonged steroid treatment to improve the clinical course of children with MPS-PS deserves further investigation

Neurotransmitter abnormalities and response to supplementation in SPG11

Objective: To report the detection of secondary neurotransmitter abnormalities in a group of SPG11 patients and describe treatment with L-dopa/carbidopa and sapropterin. Design: Case reports. Setting: National Institutes of Health in the Undiagnosed Disease Program; Children's National Medical Center in the Myelin Disorders Bioregistry Program. Patients: Four SPG11 patients with a clinical picture of progressive spastic paraparesis complicated by extrapyramidal symptoms and maculopathy. Interventions: L-Dopa/carbidopa and sapropterin. Results: 3/4 patients presented secondary neurotransmitter abnormalities; 4/4 partially responded to L-dopa as well as sapropterin. Conclusions: In the SPG11 patient with extrapyramidal symptoms, a trial of L-dopa/carbidopa and sapropterin anti/or evaluation of cerebrospinal fluid neurotransmitters should be considered

Redox Imbalance in Neurological Disorders in Adults and Children

Oxygen is a central molecule for numerous metabolic and cytophysiological processes, and, indeed, its imbalance can lead to numerous pathological consequences. In the human body, the brain is an aerobic organ and for this reason, it is very sensitive to oxygen equilibrium. The consequences of oxygen imbalance are especially devastating when occurring in this organ. Indeed, oxygen imbalance can lead to hypoxia, hyperoxia, protein misfolding, mitochondria dysfunction, alterations in heme metabolism and neuroinflammation. Consequently, these dysfunctions can cause numerous neurological alterations, both in the pediatric life and in the adult ages. These disorders share numerous common pathways, most of which are consequent to redox imbalance. In this review, we will focus on the dysfunctions present in neurodegenerative disorders (specifically Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis) and pediatric neurological disorders (X-adrenoleukodystrophies, spinal muscular atrophy, mucopolysaccharidoses and Pelizaeus-Merzbacher Disease), highlighting their underlining dysfunction in redox and identifying potential therapeutic strategies