Unusual context of CENPJ variants and primary microcephaly : compound heterozygosity and nonconsanguinity in an Argentinian patient

Primary microcephaly (MCPH) is a genetically heterogeneous disorder showing an autosomal recessive mode of inheritance. Patients with MCPH present head circumference values two or three standard deviations (SDs) significantly below the mean for age- and sex-matched populations. MCPH is associated with a nonprogressive mild to severe intellectual disability, with normal brain structure in most patients, or with a small brain and gyri without visceral malformations. We present the case of an adult patient born from Argentinian nonconsanguineous healthy parents. He had a head circumference >5 SD below the mean, cerebral neuroimaging showing hypoplasia of the corpus callosum, bilateral migration disorder with heterotopia of the sylvian fissure and colpocephaly. The patient was compound heterozygous for pathogenic variants in the CENPJ gene (c.289dupA inherited from his mother and c.1132 C > T inherited from his father). Our patient represents an uncommon situation for the usual known context of CENPJ and MCPH, including family origin (Argentinian), pedigree (nonconsanguineous), and genotype (a compound heterozygous case with two variants predicting a truncated protein). Next-generation sequencing studies applied in a broader spectrum of clinical presentations of MCPH syndromes may discover additional similar patients and families

Late-onset thymidine kinase 2 deficiency: a review of 18 cases

Mitochondrial myopathy; Multiple deletions; TK2 deficiencyMiopatia mitocondrial; Delecions múltiples; Deficiència de TK2Miopatía mitocondrial; Deleciones múltiples; Deficiencia de TK2BACKGROUND: TK2 gene encodes for mitochondrial thymidine kinase, which phosphorylates the pyrimidine nucleosides thymidine and deoxycytidine. Recessive mutations in the TK2 gene are responsible for the 'myopathic form' of the mitochondrial depletion/multiple deletions syndrome, with a wide spectrum of severity. METHODS: We describe 18 patients with mitochondrial myopathy due to mutations in the TK2 gene with absence of clinical symptoms until the age of 12. RESULTS: The mean age of onset was 31 years. The first symptom was muscle limb weakness in 10/18, eyelid ptosis in 6/18, and respiratory insufficiency in 2/18. All patients developed variable muscle weakness during the evolution of the disease. Half of patients presented difficulty in swallowing. All patients showed evidence of respiratory muscle weakness, with need for non-invasive Mechanical Ventilation in 12/18. Four patients had deceased, all of them due to respiratory insufficiency. We identified common radiological features in muscle magnetic resonance, where the most severely affected muscles were the gluteus maximus, semitendinosus and sartorius. On muscle biopsies typical signs of mitochondrial dysfunction were associated with dystrophic changes. All mutations identified were previously reported, being the most frequent the in-frame deletion p.Lys202del. All cases showed multiple mtDNA deletions but mtDNA depletion was present only in two patients. CONCLUSIONS: The late-onset is the less frequent form of presentation of the TK2 deficiency and its natural history is not well known. Patients with late onset TK2 deficiency have a consistent and recognizable clinical phenotype and a poor prognosis, due to the high risk of early and progressive respiratory insufficiency

A method for multiplexed full-length single-molecule sequencing of the human mitochondrial genome

Data processing; DNA sequencing; Genomic analysisTratamiento de datos; Secuenciación de ADN; Análisis genómicoTractament de dades; Seqüenciació d'ADN; Anàlisi genòmicaMethods to reconstruct the mitochondrial DNA (mtDNA) sequence using short-read sequencing come with an inherent bias due to amplification and mapping. They can fail to determine the phase of variants, to capture multiple deletions and to cover the mitochondrial genome evenly. Here we describe a method to target, multiplex and sequence at high coverage full-length human mitochondrial genomes as native single-molecules, utilizing the RNA-guided DNA endonuclease Cas9. Combining Cas9 induced breaks, that define the mtDNA beginning and end of the sequencing reads, as barcodes, we achieve high demultiplexing specificity and delineation of the full-length of the mtDNA, regardless of the structural variant pattern. The long-read sequencing data is analysed with a pipeline where our custom-developed software, baldur, efficiently detects single nucleotide heteroplasmy to below 1%, physically determines phase and can accurately disentangle complex deletions. Our workflow is a tool for studying mtDNA variation and will accelerate mitochondrial research.This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 824110 – EASI-Genomics (I.G.G.) and the ERC Synergy project BCLL@las under grant agreement No 810287 (I.G.G.). Institutional support was from the Spanish Instituto de Salud Carlos III, Fondo de Investigaciones Sanitarias and cofunded with ERDF funds (PI19/01772). We acknowledge the institutional support of the Spanish Ministry of Science and Innovation through the Instituto de Salud Carlos III and the 2014–2020 Smart Growth Operating Program, to the EMBL partnership and institutional co-financing with the European Regional Development Fund (MINECO/FEDER, BIO2015-71792-P). We also acknowledge the support of the Centro de Excelencia Severo Ochoa, and the Generalitat de Catalunya through the Departament de Salut, Departament d’Empresa i Coneixement and the CERCA Programme to the institute

Leigh syndrome associated with TRMU gene mutations

Insuficiència hepàtica aguda: Síndrome de Leigh; TRMUInsuficiencia hepática aguda; Síndrome de Leigh; TRMUAcute liver failure; Leigh syndrome; TRMUtRNA 5-methylaminomethyl-2-thiouridylate methyltransferase (TRMU) deficiency causes an early onset potentially reversible acute liver failure, so far reported in less than 30 patients. We describe two new unrelated patients with an acute liver failure and a neuroimaging compatible with Leigh syndrome (LS) due to TRMU deficiency, a combination not previously reported. Our report enlarges the phenotypical spectrum of TRMU disease.This work was partially supported by the Spanish Instituto de Salud Carlos III, Fondo de Investigaciones Sanitarias and cofounded with ERDF funds (Grant No. FIS PI15/01428, PI19/01772)

The Eutherian Armcx genes regulate mitochondrial trafficking in neurons and interact with Miro and Trak2

Producción CientíficaBrain function requires neuronal activity-dependent energy consumption. Neuronal energy supply is controlled by molecular mechanisms that regulate mitochondrial dynamics, including Kinesin motors and Mitofusins, Miro1-2 and Trak2 proteins. Here we show a new protein family that localizes to the mitochondria and controls mitochondrial dynamics. This family of proteins is encoded by an array of armadillo (Arm) repeat-containing genes located on the X chromosome. The Armcx cluster is unique to Eutherian mammals and evolved from a single ancestor gene (Armc10). We show that these genes are highly expressed in the developing and adult nervous system. Furthermore, we demonstrate that Armcx3 expression levels regulate mitochondrial dynamics and trafficking in neurons, and that Alex3 interacts with the Kinesin/Miro/Trak2 complex in a Ca2 + -dependent manner. Our data provide evidence of a new Eutherian-specific family of mitochondrial proteins that controls mitochondrial dynamics and indicate that this key process is differentially regulated in the brain of higher vertebrates.2015-03-3

An Atypical Presentation of Upper Motor Neuron Predominant Juvenile Amyotrophic Lateral Sclerosis Associated with TARDBP Gene: A Case Report and Review of the Literature

Juvenile amyotrophic lateral sclerosis; Predominant disorderEsclerosi lateral amiotròfica juvenil; Trastorn predominantEsclerosis lateral amiotrófica juvenil; Trastorno predominanteAmyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that can rarely affect young individuals. Juvenile ALS (JALS) is defined for individuals with an onset of the disease before the age of 25. The contribution of genetics to ALS pathology is a field of growing interest. One of the differences between adult-onset ALS and JALS is their genetic background, with a higher contribution of genetic causes in JALS. We report a patient with JALS and a pathogenic variant in the TARDBP gene (c.1035C > G; p.Asn345Lys), previously reported only in adult-onset ALS, and with an atypical phenotype of marked upper motor neuron predominance. In addition, the proband presented an additional variant in the NEK1 gene, c.2961C > G (p.Phe987Leu), which is classified as a variant of unknown significance. Segregation studies showed a paternal origin of the TARDBP variant, while the variant in NEK1 was inherited from the mother. We hypothesize that the NEK1 variant acts as a disease modifier and suggests the possibility of a functional interaction between both genes in our case. This hypothesis could explain the peculiarities of the phenotype, penetrance, and the age of onset. This report highlights the heterogeneity of the phenotypic presentation of ALS associated with diverse pathogenic genetic variants

Leigh Syndrome Associated with TRMU Gene Mutations

tRNA 5-methylaminomethyl-2-thiouridylate methyltransferase (TRMU) deficiency causes an early onset potentially reversible acute liver failure, so far reported in less than 30 patients. We describe two new unrelated patients with an acute liver failure and a neuroimaging compatible with Leigh syndrome (LS) due to TRMU deficiency, a combination not previously reported. Our report enlarges the phenotypical spectrum of TRMU diseaseThe Centro de Investigacion Biomedica en Red de Enfermedades Raras (CIBERER), is an initiative of the Instituto de Salud Carlos III (Ministerio de Ciencia e Innovacion, Spain). This study was supported by the Agencia de Gestio d'Ajuts Universitaris i de Recerca (AGAUR) (2014: SGR 393) and the CERCA Programme/Generalitat de Catalunya. The present study was supported by the Department de Salut, Generalitat de Catalunya (URDCAT project, SLT002/16/00174

Oxidative damage compromises energy metabolism in the axonal degeneration mouse model of X-adrenoleukodystrophy

Aims: Chronic metabolic impairment and oxidative stress are associated with the pathogenesis of axonal dysfunction in a growing number of neurodegenerative conditions. To investigate the intertwining of both noxious factors, we have chosen the mouse model of adrenoleukodystrophy (X-ALD), which exhibits axonal degeneration in spinal cords and motor disability. The disease is caused by loss of function of the ABCD1 transporter, involved in the import and degradation of very long-chain fatty acids (VLCFA) in peroxisomes. Oxidative stress due to VLCFA excess appears early in the neurodegenerative cascade. Results: In this study, we demonstrate by redox proteomics that oxidative damage to proteins specifically affects five key enzymes of glycolysis and TCA (Tricarboxylic acid) cycle in spinal cords of Abcd1(-) mice and pyruvate kinase in human X-ALD fibroblasts. We also show that NADH and ATP levels are significantly diminished in these samples, together with decrease of pyruvate kinase activities and GSH levels, and increase of NADPH. Innovation: Treating Abcd1(-) mice with the antioxidants N-acetylcysteine and alpha-lipoic acid (LA) prevents protein oxidation; preserves NADH, NADPH, ATP, and GSH levels; and normalizes pyruvate kinase activity, which implies that oxidative stress provoked by VLCFA results in bioenergetic dysfunction, at a presymptomatic stage. Conclusion: Our results provide mechanistic insight into the beneficial effects of antioxidants and enhance the rationale for translation into clinical trials for X-adrenoleukodystrophy. Antioxid. Redox Signal. 15, 2095-2107

Multicentric Standardization of Protocols for the Diagnosis of Human Mitochondrial Respiratory Chain Defects

The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Institutional Review Board of each institution: IBC U737 (C0000128), HCL U722 (HCB2017/0808), 12O U723 (CEI:18/487), VH U701 (PR(IR)63/2016) and UPO U729 (C.I. 2768-N-21)The quantification of mitochondrial respiratory chain (MRC) enzymatic activities is essential for diagnosis of a wide range of mitochondrial diseases, ranging from inherited defects to secondary dysfunctions. MRC lesion is frequently linked to extended cell damage through the generation of proton leak or oxidative stress, threatening organ viability and patient health. However, the intrinsic challenge of a methodological setup and the high variability in measuring MRC enzymatic activities represents a major obstacle for comparative analysis amongst institutions. To improve experimental and statistical robustness, seven Spanish centers with extensive experience in mitochondrial research and diagnosis joined to standardize common protocols for spectrophotometric MRC enzymatic measurements using minimum amounts of sample. Herein, we present the detailed protocols, reference ranges, tips and troubleshooting methods for experimental and analytical setups in different sample preparations and tissues that will allow an international standardization of common protocols for the diagnosis of MRC defects. Methodological standardization is a crucial step to obtain comparable reference ranges and international standards for laboratory assays to set the path for further diagnosis and research in the field of mitochondrial diseasesThis work was supported by Instituto de Salud Carlos III (ISCIII), grants FIS PI17/00021, PI17/00359, PI18/00498, PI18/00451, PI18/01374, PI19/01772, PI20/00541, PI21/00229, PI21/00381 and PI21/00935 (ISCIII-FEDER “Cofinanciado por la Unión Europea”), Fundació Privada Cellex, Junta de Andalucía (UPO-1262247) and Ministerio de Ciencia e Innovación (MCINN) grant PID2019-110320RBI00. All participant centers are integrated in the Centro de Investigación Biomédica en Red (CIBER), Sección de Enfermedades Raras (CIBERER, an initiative of ISCIII), which is the founder of this present methodological stud