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1.
Am J Hum Genet ; 105(2): 434-440, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31374204

RESUMO

Brittle and "tiger-tail" hair is the diagnostic hallmark of trichothiodystrophy (TTD), a rare recessive disease associated with a wide spectrum of clinical features including ichthyosis, intellectual disability, decreased fertility, and short stature. As a result of premature abrogation of terminal differentiation, the hair is brittle and fragile and contains reduced cysteine content. Hypersensitivity to UV light is found in about half of individuals with TTD; all of these individuals harbor bi-allelic mutations in components of the basal transcription factor TFIIH, and these mutations lead to impaired nucleotide excision repair and basal transcription. Different genes have been found to be associated with non-photosensitive TTD (NPS-TTD); these include MPLKIP (also called TTDN1), GTF2E2 (also called TFIIEß), and RNF113A. However, a relatively large group of these individuals with NPS-TTD have remained genetically uncharacterized. Here we present the identification of an NPS-TTD-associated gene, threonyl-tRNA synthetase (TARS), found by next-generation sequencing of a group of uncharacterized individuals with NPS-TTD. One individual has compound heterozygous TARS variants, c.826A>G (p.Lys276Glu) and c.1912C>T (p.Arg638∗), whereas a second individual is homozygous for the TARS variant: c.680T>C (p.Leu227Pro). We showed that these variants have a profound effect on TARS protein stability and enzymatic function. Our results expand the spectrum of genes involved in TTD to include genes implicated in amino acid charging of tRNA, which is required for the last step in gene expression, namely protein translation. We previously proposed that some of the TTD-specific features derive from subtle transcription defects as a consequence of unstable transcription factors. We now extend the definition of TTD from a transcription syndrome to a "gene-expression" syndrome.

2.
J Inherit Metab Dis ; 42(5): 1030-1039, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31032972

RESUMO

Murine succinic semialdehyde dehydrogenase deficiency (SSADHD) manifests with high concentrations of γ-aminobutyric acid (GABA) and γ-hydroxybutyrate (GHB) and low glutamine in the brain. To understand the pathogenic contribution of central glutamine deficiency, we exposed aldh5a1-/- (SSADHD) mice and their genetic controls (aldh5a1+/+ ) to either a 4% (w/w) glutamine-containing diet or a glutamine-free diet from conception until postnatal day 30. Endpoints included brain, liver and blood amino acids, brain GHB, ataxia scores, and open field testing. Glutamine supplementation did not improve aldh5a1-/- brain glutamine deficiency nor brain GABA and GHB. It decreased brain glutamate but did not change the ratio of excitatory (glutamate) to inhibitory (GABA) neurotransmitters. In contrast, glutamine supplementation significantly increased brain arginine (30% for aldh5a1+/+ and 18% for aldh5a1-/- mice), and leucine (12% and 18%). Glutamine deficiency was confirmed in the liver. The test diet increased hepatic glutamate in both genotypes, decreased glutamine in aldh5a1+/+ but not in aldh5a1-/- , but had no effect on GABA. Dried bloodspot analyses showed significantly elevated GABA in mutants (approximately 800% above controls) and decreased glutamate (approximately 25%), but no glutamine difference with controls. Glutamine supplementation did not impact blood GABA but significantly increased glutamine and glutamate in both genotypes indicating systemic exposure to dietary glutamine. Ataxia and pronounced hyperactivity were observed in aldh5a1-/- mice but remained unchanged by the diet intervention. The study suggests that glutamine supplementation improves peripheral but not central glutamine deficiency in experimental SSADHD. Future studies are needed to fully understand the pathogenic role of brain glutamine deficiency in SSADHD.

3.
Am J Hum Genet ; 104(3): 520-529, 2019 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-30824121

RESUMO

Aminoacyl-tRNA synthetases (ARSs) are essential enzymes responsible for charging tRNA molecules with cognate amino acids. Consistent with the essential function and ubiquitous expression of ARSs, mutations in 32 of the 37 ARS-encoding loci cause severe, early-onset recessive phenotypes. Previous genetic and functional data suggest a loss-of-function mechanism; however, our understanding of the allelic and locus heterogeneity of ARS-related disease is incomplete. Cysteinyl-tRNA synthetase (CARS) encodes the enzyme that charges tRNACys with cysteine in the cytoplasm. To date, CARS variants have not been implicated in any human disease phenotype. Here, we report on four subjects from three families with complex syndromes that include microcephaly, developmental delay, and brittle hair and nails. Each affected person carries bi-allelic CARS variants: one individual is compound heterozygous for c.1138C>T (p.Gln380∗) and c.1022G>A (p.Arg341His), two related individuals are compound heterozygous for c.1076C>T (p.Ser359Leu) and c.1199T>A (p.Leu400Gln), and one individual is homozygous for c.2061dup (p.Ser688Glnfs∗2). Measurement of protein abundance, yeast complementation assays, and assessments of tRNA charging indicate that each CARS variant causes a loss-of-function effect. Compared to subjects with previously reported ARS-related diseases, individuals with bi-allelic CARS variants are unique in presenting with a brittle-hair-and-nail phenotype, which most likely reflects the high cysteine content in human keratins. In sum, our efforts implicate CARS variants in human inherited disease, expand the locus and clinical heterogeneity of ARS-related clinical phenotypes, and further support impaired tRNA charging as the primary mechanism of recessive ARS-related disease.

4.
Hum Mutat ; 40(7): 975-982, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30908763

RESUMO

D-2-hydroxyglutaric aciduria Type I (D-2-HGA Type I), a neurometabolic disorder with a broad clinical spectrum, is caused by recessive variants in the D2HGDH gene encoding D-2-hydroxyglutarate dehydrogenase (D-2-HGDH). We and others detected 42 potentially pathogenic variants in D2HGDH of which 31 were missense. We developed functional studies to investigate the effect of missense variants on D-2-HGDH catalytic activity. Site-directed mutagenesis was used to introduce 31 missense variants in the pCMV5-D2HGDH expression vector. The wild type and missense variants were overexpressed in HEK293 cells. D-2-HGDH enzyme activity was evaluated based on the conversion of [2 H4 ]D-2-HG to [2 H4 ]2-ketoglutarate, which was subsequently converted into [2 H4 ]L-glutamate and the latter quantified by LC-MS/MS. Eighteen variants resulted in almost complete ablation of D-2-HGDH activity and thus, should be considered pathogenic. The remaining 13 variants manifested residual activities ranging between 17% and 94% of control enzymatic activity. Our functional assay evaluating the effect of novel D2HGDH variants will be beneficial for the classification of missense variants and determination of pathogenicity.

5.
Neurochem Int ; 125: 151-162, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30822440

RESUMO

The anticonvulsant vigabatrin (VGB; SabrilR) irreversibly inhibits GABA transaminase to increase neural GABA, yet its mechanism of retinal toxicity remains unclear. VGB is suggested to alter several amino acids, including homocarnosine, ß-alanine, ornithine, glycine, taurine, and 2-aminoadipic acid (AADA), the latter a homologue of glutamic acid. Here, we evaluate the effect of VGB on amino acid concentrations in mice, employing a continuous VGB infusion (subcutaneously implanted osmotic minipumps), dose-escalation paradigm (35-140 mg/kg/d, 12 days), and amino acid quantitation in eye, visual and prefrontal cortex, total brain, liver and plasma. We hypothesized that continuous VGB dosing would reveal numerous hitherto undescribed amino acid disturbances. Consistent amino acid elevations across tissues included GABA, ß-alanine, carnosine, ornithine and AADA, as well as neuroactive aspartic and glutamic acids, serine and glycine. Maximal increase of AADA in eye occurred at 35 mg/kg/d (41 ±â€¯2 nmol/g (n = 21, vehicle) to 60 ±â€¯8.5 (n = 8)), and at 70 mg/kg/d for brain (97 ±â€¯6 (n = 21) to 145 ±â€¯6 (n = 6)), visual cortex (128 ±â€¯6 to 215 ±â€¯19) and prefrontal cortex (124 ±â€¯11 to 200 ±â€¯13; mean ±â€¯SEM; p < 0.05), the first demonstration of tissue AADA accumulation with VGB in mammal. VGB effects on basic amino acids, including guanidino-species, suggested the capacity of VGB to alter urea cycle function and nitrogen disposal. The known toxicity of AADA in retinal glial cells highlights new avenues for assessing VGB retinal toxicity and other off-target effects.

6.
Nat Commun ; 10(1): 707, 2019 02 12.
Artigo em Inglês | MEDLINE | ID: mdl-30755602

RESUMO

Aminoacyl-tRNA synthetases (ARSs) function to transfer amino acids to cognate tRNA molecules, which are required for protein translation. To date, biallelic mutations in 31 ARS genes are known to cause recessive, early-onset severe multi-organ diseases. VARS encodes the only known valine cytoplasmic-localized aminoacyl-tRNA synthetase. Here, we report seven patients from five unrelated families with five different biallelic missense variants in VARS. Subjects present with a range of global developmental delay, epileptic encephalopathy and primary or progressive microcephaly. Longitudinal assessment demonstrates progressive cortical atrophy and white matter volume loss. Variants map to the VARS tRNA binding domain and adjacent to the anticodon domain, and disrupt highly conserved residues. Patient primary cells show intact VARS protein but reduced enzymatic activity, suggesting partial loss of function. The implication of VARS in pediatric neurodegeneration broadens the spectrum of human diseases due to mutations in tRNA synthetase genes.


Assuntos
Epilepsia/genética , Mutação , Valina-tRNA Ligase/genética , Alelos , Anticódon , Criança , Pré-Escolar , Progressão da Doença , Epilepsia/enzimologia , Epilepsia/patologia , Feminino , Predisposição Genética para Doença , Humanos , Estudos Longitudinais , Mutação com Perda de Função , Masculino , Microcefalia/enzimologia , Microcefalia/genética , Modelos Moleculares , Transtornos do Neurodesenvolvimento/enzimologia , Transtornos do Neurodesenvolvimento/genética , Transtornos do Neurodesenvolvimento/patologia , Linhagem , Biossíntese de Proteínas , Domínios e Motivos de Interação entre Proteínas , RNA de Transferência/genética , Sequenciamento Completo do Exoma , Sequenciamento Completo do Genoma
7.
J Inherit Metab Dis ; 42(1): 147-158, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30740741

RESUMO

BACKGROUND: Transaldolase deficiency (TALDO-D) is a rare autosomal recessive inborn error of the pentose phosphate pathway. Since its first description in 2001, several case reports have been published, but there has been no comprehensive overview of phenotype, genotype, and phenotype-genotype correlation. METHODS: We performed a retrospective questionnaire and literature study of clinical, biochemical, and molecular data of 34 patients from 25 families with proven TALDO-D. In some patients, endocrine abnormalities have been found. To further evaluate these abnormalities, we performed biochemical investigations on blood of 14 patients. RESULTS AND CONCLUSIONS: Most patients (n = 22) had an early-onset presentation (prenatally or before 1 month of age); 12 patients had a late-onset presentation (3 months to 9 years). Main presenting symptoms were intrauterine growth restriction, dysmorphic facial features, congenital heart disease, anemia, thrombocytopenia, and hepato(spleno)megaly. An older sib of two affected patients was asymptomatic until the age of 9 years, and only after molecular diagnosis was hepatomegaly noted. In some patients, there was gonadal dysfunction with low levels of testosterone and secondary luteinizing hormone (LH) and follicle-stimulating hormone (FSH) abnormalities later in life. This overview provides information that can be helpful for managing patients and counseling families regarding prognosis. Diagnostic guidelines, possible genotype-phenotype correlations, treatment options, and pathophysiological disease mechanisms are proposed.

8.
Neurology ; 92(11): e1225-e1237, 2019 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-30737337

RESUMO

OBJECTIVE: To describe the leukodystrophy caused by pathogenic variants in LARS2 and KARS, encoding mitochondrial leucyl transfer RNA (tRNA) synthase and mitochondrial and cytoplasmic lysyl tRNA synthase, respectively. METHODS: We composed a group of 5 patients with leukodystrophy, in whom whole-genome or whole-exome sequencing revealed pathogenic variants in LARS2 or KARS. Clinical information, brain MRIs, and postmortem brain autopsy data were collected. We assessed aminoacylation activities of purified mutant recombinant mitochondrial leucyl tRNA synthase and performed aminoacylation assays on patients' lymphoblasts and fibroblasts. RESULTS: Patients had a combination of early-onset deafness and later-onset neurologic deterioration caused by progressive brain white matter abnormalities on MRI. Female patients with LARS2 pathogenic variants had premature ovarian failure. In 2 patients, MRI showed additional signs of early-onset vascular abnormalities. In 2 other patients with LARS2 and KARS pathogenic variants, magnetic resonance spectroscopy revealed elevated white matter lactate, suggesting mitochondrial disease. Pathology in one patient with LARS2 pathogenic variants displayed evidence of primary disease of oligodendrocytes and astrocytes with lack of myelin and deficient astrogliosis. Aminoacylation activities of purified recombinant mutant leucyl tRNA synthase showed a 3-fold loss of catalytic efficiency. Aminoacylation assays on patients' lymphoblasts and fibroblasts showed about 50% reduction of enzyme activity. CONCLUSION: This study adds LARS2 and KARS pathogenic variants as gene defects that may underlie deafness, ovarian failure, and leukodystrophy with mitochondrial signature. We discuss the specific MRI characteristics shared by leukodystrophies caused by mitochondrial tRNA synthase defects. We propose to add aminoacylation assays as biochemical diagnostic tools for leukodystrophies.

9.
Pharmacol Res Perspect ; 7(1): e00456, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30631446

RESUMO

Vigabatrin (VGB; (S)-(+)/(R)-(-) 4-aminohex-5-enoic acid), an antiepileptic irreversibly inactivating GABA transaminase (GABA-T), manifests use-limiting ocular toxicity. Hypothesizing that the active S enantiomer of VGB would preferentially accumulate in eye and visual cortex (VC) as one potential mechanism for ocular toxicity, we infused racemic VGB into mice via subcutaneous minipump at 35, 70, and 140 mg/kg/d (n = 6-8 animals/dose) for 12 days. VGB enantiomers, total GABA and ß-alanine (BALA), 4-guanidinobutyrate (4-GBA), and creatine were quantified by mass spectrometry in eye, brain, liver, prefrontal cortex (PFC), and VC. Plasma VGB concentrations increased linearly by dose (3 ± 0.76 (35 mg/kg/d); 15.1 ± 1.4 (70 mg/kg/d); 34.6 ± 3.2 µmol/L (140 mg/kg/d); mean ± SEM) with an S/R ratio of 0.74 ± 0.02 (n = 14). Steady state S/R ratios (35, 70 mg/kg/d doses) were highest in eye (5.5 ± 0.2; P < 0.0001), followed by VC (3.9 ± 0.4), PFC (3.6 ± 0.3), liver (2.9 ± 0.1), and brain (1.5 ± 0.1; n = 13-14 each). Total VGB content of eye exceeded that of brain, PFC and VC at all doses. High-dose VGB diminished endogenous metabolite production, especially in PFC and VC. GABA significantly increased in all tissues (all doses) except brain; BALA increases were confined to liver and VC; and 4-GBA was prominently increased in brain, PFC and VC (and eye at high dose). Linear correlations between enantiomers and GABA were observed in all tissues, but only in PFC/VC for BALA, 4-GBA, and creatine. Preferential accumulation of the VGB S isomer in eye and VC may provide new insight into VGB ocular toxicity.


Assuntos
Anticonvulsivantes/farmacocinética , Vigabatrina/farmacocinética , Transtornos da Visão/prevenção & controle , 4-Aminobutirato Transaminase/antagonistas & inibidores , Animais , Anticonvulsivantes/efeitos adversos , Anticonvulsivantes/química , Avaliação Pré-Clínica de Medicamentos , Olho/efeitos dos fármacos , Olho/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Modelos Animais , Estereoisomerismo , Distribuição Tecidual , Vigabatrina/efeitos adversos , Vigabatrina/química , Transtornos da Visão/induzido quimicamente , Córtex Visual/efeitos dos fármacos , Córtex Visual/metabolismo , Campos Visuais/efeitos dos fármacos
10.
J Inherit Metab Dis ; 2018 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-30043187

RESUMO

Pyridoxine dependent epilepsy (PDE) is a treatable epileptic encephalopathy characterized by a positive response to pharmacologic doses of pyridoxine. Despite seizure control, at least 75% of individuals have intellectual disability and developmental delay. Current treatment paradigms have resulted in improved cognitive outcomes emphasizing the importance of an early diagnosis. As genetic testing is increasingly accepted as first tier testing for epileptic encephalopathies, we aimed to provide a comprehensive overview of ALDH7A1 mutations that cause PDE. The genotypes, ethnic origin, and reported gender was collected from 185 subjects with a diagnosis of PDE. The population frequency for the variants in this report and the existing literature were reviewed in the Genome Aggregation Database (gnomAD). Novel variants identified in population databases were also evaluated through in silico prediction software and select variants were over-expressed in an E.coli-based expression system to measure α-aminoadipic semialdehyde dehydrogenase activity and production of α-aminoadipic acid. This study adds 47 novel variants to the literature resulting in a total of 165 reported pathogenic variants. Based on this report, in silico predictions, and general population data, we estimate an incidence of approximately 1:64,352 live births. This report provides a comprehensive overview of known ALDH7A1 mutations that cause PDE, and suggests that PDE may be more common than initially estimated. Due to the relative high frequency of the disease, the likelihood of under-diagnosis given the wide clinical spectrum and limited awareness among clinicians as well as the cognitive improvement noted with early treatment, newborn screening for PDE may be warranted.

11.
PLoS One ; 13(6): e0199737, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29953513

RESUMO

INTRODUCTION: The gene encoding isocitrate dehydrogenase 1 (IDH1) is frequently mutated in several tumor types including gliomas. The most prevalent mutation in gliomas is a missense mutation leading to a substitution of arginine with histidine at the residue 132 (R132H). Wild type IDH1 catalyzes oxidative decarboxylation of isocitrate to α-ketoglutarate (α-KG) whereas mutant IDH1 converts α-KG into D2-hydroxyglutarate (D2HG). Unfortunately, there are few in vivo model systems for IDH-mutated tumors to study the effects of IDH1 mutations in tumor development. We have therefore created transgenic zebrafish lines that express various IDH1 mutants. MATERIALS AND METHODS: IDH1 mutations (IDH1R132H, IDH1R132C and loss-of-function mutation IDH1G70D), IDH1wildtype or eGFP were cloned into constructs with several brain-specific promoters (Nestin, Gfap or Gata2). These constructs were injected into fertilized zebrafish eggs at the one-cell stage. RESULTS: In total more than ten transgenic zebrafish lines expressing various brain-specific IDH1 mutations were created. A significant increase in the level of D2HG was observed in all transgenic lines expressing IDH1R132C or IDH1R132H, but not in any of the lines expressing IDH1wildtype, IDH1G70D or eGFP. No differences in 5-hydroxymethyl cytosine and mature collagen IV levels were observed between wildtype and mutant IDH1 transgenic fish. To our surprise, we failed to identify any strong phenotype, despite increased levels of the oncometabolite D2HG. No tumors were observed, even when backcrossing with tp53-mutant fish which suggests that additional transforming events are required for tumor formation. Elevated D2HG levels could be lowered by treatment of the transgenic zebrafish with an inhibitor of mutant IDH1 activity. CONCLUSIONS: We have generated a transgenic zebrafish model system for mutations in IDH1 that can be used for functional analysis and drug screening. Our model systems help understand the biology of IDH1 mutations and its role in tumor formation.

12.
JIMD Rep ; 2018 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-29654543

RESUMO

BACKGROUND: Mutations in SLC25A4 (syn. ANT1, Adenine nucleotide translocase, type 1) are known to cause either autosomal dominant progressive external ophthalmoplegia (adPEO) or recessive mitochondrial myopathy, hypertrophic cardiomyopathy, and lactic acidosis. METHODS AND RESULTS: Whole exome sequencing in a young man with myopathy, subsarcolemmal mitochondrial aggregations, cardiomyopathy, lactic acidosis, and L-2-hydroxyglutaric aciduria (L-2-HGA) revealed a new homozygous mutation in SLC25A4 [c.653A>C, NM_001151], leading to the replacement of a highly conserved glutamine by proline [p.(Q218P); NP_001142] that most likely affects the folding of the ANT1 protein. No pathogenic mutation was found in L2HGDH, which is associated with "classic" L-2-HGA. Furthermore, L-2-HGDH enzymatic activity in the patient fibroblasts was normal. Long-range PCR and Southern blot confirmed absence of mtDNA-deletions in blood and muscle. CONCLUSION: The disturbed ADP/ATP transport across the inner mitochondrial membrane may lead to an accumulation of different TCA-cycle intermediates such as 2-ketoglutarate (2-KG) in our patient. As L-2-HG is generated from 2-KG we hypothesize that the L-2-HG increase is a secondary effect of 2-KG accumulation. Hence, our report expands the spectrum of laboratory findings in ANT1-related diseases and hints towards a connection with organic acidurias.

13.
Am J Hum Genet ; 102(4): 676-684, 2018 04 05.
Artigo em Inglês | MEDLINE | ID: mdl-29576217

RESUMO

Hypomyelinating leukodystrophies are genetic disorders characterized by insufficient myelin deposition during development. They are diagnosed on the basis of both clinical and MRI features followed by genetic confirmation. Here, we report on four unrelated affected individuals with hypomyelination and bi-allelic pathogenic variants in EPRS, the gene encoding cytoplasmic glutamyl-prolyl-aminoacyl-tRNA synthetase. EPRS is a bifunctional aminoacyl-tRNA synthetase that catalyzes the aminoacylation of glutamic acid and proline tRNA species. It is a subunit of a large multisynthetase complex composed of eight aminoacyl-tRNA synthetases and its three interacting proteins. In total, five different EPRS mutations were identified. The p.Pro1115Arg variation did not affect the assembly of the multisynthetase complex (MSC) as monitored by affinity purification-mass spectrometry. However, immunoblot analyses on protein extracts from fibroblasts of the two affected individuals sharing the p.Pro1115Arg variant showed reduced EPRS amounts. EPRS activity was reduced in one affected individual's lymphoblasts and in a purified recombinant protein model. Interestingly, two other cytoplasmic aminoacyl-tRNA synthetases have previously been implicated in hypomyelinating leukodystrophies bearing clinical and radiological similarities to those in the individuals we studied. We therefore hypothesized that leukodystrophies caused by mutations in genes encoding cytoplasmic aminoacyl-tRNA synthetases share a common underlying mechanism, such as reduced protein availability, abnormal assembly of the multisynthetase complex, and/or abnormal aminoacylation, all resulting in reduced translation capacity and insufficient myelin deposition in the developing brain.

14.
Eur J Paediatr Neurol ; 22(3): 369-379, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29506905

RESUMO

PURPOSE: Guanidinoacetate methyltransferase (GAMT) deficiency is an autosomal recessive disorder caused by pathogenic variants in GAMT. Brain creatine depletion and guanidinoacetate accumulation cause developmental delay, seizures and movement disorder. Treatment consists of creatine, ornithine and arginine-restricted diet. We initiated an international treatment registry using Research Electronic Data Capture (REDCap) software to evaluate treatment outcome. METHODS: Physicians completed an online REDCap questionnaire. Clinical severity score applied pre-treatment and on treatment. RESULTS: There were 22 patients. All had developmental delay, 18 had seizures and 8 had movement disorder. Based on the clinical severity score, 5 patients had a severe, 14 patients had a moderate and 3 patients had a mild phenotype. All patients had pathogenic variants in GAMT. The phenotype ranged from mild to moderate in patients with the most common c.327G > A variant. The phenotype ranged from mild to severe in patients with truncating variants. All patients were on creatine, 18 patients were on ornithine and 15 patients were on arginine- or protein-restricted diet. Clinical severity score improved in 13 patients on treatment. Developmental delay improved in five patients. One patient achieved normal development. Eleven patients became seizure free. Movement disorder resolved in four patients. CONCLUSION: In our small patient cohort, there seems to be no phenotype-genotype correlation. Creatine and ornithine and/or arginine- or protein-restricted diet were the most useful treatment to improve phenotype.


Assuntos
Guanidinoacetato N-Metiltransferase/deficiência , Transtornos do Desenvolvimento da Linguagem/dietoterapia , Transtornos dos Movimentos/congênito , Estudos de Coortes , Creatina/administração & dosagem , Dieta com Restrição de Proteínas/métodos , Feminino , Humanos , Transtornos do Desenvolvimento da Linguagem/complicações , Masculino , Transtornos dos Movimentos/complicações , Transtornos dos Movimentos/dietoterapia , Ornitina/administração & dosagem , Estudos Retrospectivos , Convulsões/tratamento farmacológico , Convulsões/etiologia , Resultado do Tratamento
15.
Eur J Hum Genet ; 26(4): 537-551, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29440775

RESUMO

This study aims to identify gene defects in pediatric cardiomyopathy and early-onset brain disease with oxidative phosphorylation (OXPHOS) deficiencies. We applied whole-exome sequencing in three patients with pediatric cardiomyopathy and early-onset brain disease with OXPHOS deficiencies. The brain pathology was studied by MRI analysis. In consanguineous patient 1, we identified a homozygous intronic variant (c.850-3A > G) in the QRSL1 gene, which was predicted to cause abnormal splicing. The variant segregated with the disease and affected the protein function, which was confirmed by complementation studies, restoring OXPHOS function only with wild-type QRSL1. Patient 2 was compound heterozygous for two novel affected and disease-causing variants (c.[253G > A];[938G > A]) in the MTO1 gene. In patient 3, we detected one unknown affected and disease-causing variants (c.2872C > T) and one known disease-causing variant (c.1774C > T) in the AARS2 gene. The c.1774C > T variant was present in the paternal copy of the AARS2 gene, the c.2872C > T in the maternal copy. All genes were involved in translation of mtDNA-encoded proteins. Defects in mtDNA-encoded protein translation lead to severe pediatric cardiomyopathy and brain disease with OXPHOS abnormalities. This suggests that the heart and brain are particularly sensitive to defects in mitochondrial protein synthesis during late embryonic or early postnatal development, probably due to the massive mitochondrial biogenesis occurring at that stage. If both the heart and brain are involved, the prognosis is poor with a likely fatal outcome at young age.

16.
Metab Brain Dis ; 33(3): 875-884, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29435807

RESUMO

To evaluate the outcome of current treatment for creatine transporter (CRTR) deficiency, we developed a clinical severity score and initiated an international treatment registry. An online questionnaire was completed by physicians following patients with CRTR deficiency on a treatment, including creatine and/or arginine, and/or glycine. Clinical severity score included 1) global developmental delay/intellectual disability; 2) seizures; 3) behavioural disorder. Phenotype scored 1-3 = mild; 4-6 = moderate; and 7-9 = severe. We applied the clinical severity score pre- and on-treatment. Seventeen patients, 14 males and 3 females, from 16 families were included. Four patients had severe, 6 patients had moderate, and 7 patients had a mild phenotype. The phenotype ranged from mild to severe in patients diagnosed at or before 2 years of age or older than 6 years of age. The phenotype ranged from mild to severe in patients with mildly elevated urine creatine to creatinine ratio. Fourteen patients were on the combined creatine, arginine and glycine therapy. On the combined treatment with creatine, arginine and glycine, none of the males showed either deterioration or improvements in their clinical severity score, whereas two females showed improvements in the clinical severity score. Creatine monotherapy resulted in deterioration of the clinical severity score in one male. There seems to be no correlation between phenotype and degree of elevation in urine creatine to creatinine ratio, genotype, or age at diagnosis. Combined creatine, arginine and glycine therapy might have stopped disease progression in males and improved phenotype in females.

17.
Can J Neurol Sci ; 45(1): 93-96, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-29144225

RESUMO

Between July of 2012 and December of 2014, 39 patients were enrolled prospectively to investigate the prevalence of glucose transporter 1 (GLUT1) deficiency in a ketogenic diet clinic. None of them had GLUT1 deficiency. All patients seen in the same clinic within the same period were reviewed retrospectively. A total of 18 of these 85 patients had a genetic diagnosis, including GLUT1 deficiency, pathogenic copy number variants, congenital disorder of glycosylation, neuronal ceroid lipofuscinosis type II, mitochondrial disorders, tuberous sclerosis, lissencephaly, and SCN1A-, SCN8A-, and STXBP1-associated epileptic encephalopathies. The prevalence of genetic diagnoses was 21% and prevalence of GLUT1 deficiency was 2.4% in our retrospective cohort study.

18.
J Inherit Metab Dis ; 41(2): 169-180, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29238895

RESUMO

Combined D-2- and L-2-hydroxyglutaric aciduria (D/L-2-HGA) is a devastating neurometabolic disorder, usually lethal in the first years of life. Autosomal recessive mutations in the SLC25A1 gene, which encodes the mitochondrial citrate carrier (CIC), were previously detected in patients affected with combined D/L-2-HGA. We showed that transfection of deficient fibroblasts with wild-type SLC25A1 restored citrate efflux and decreased intracellular 2-hydroxyglutarate levels, confirming that deficient CIC is the cause of D/L-2-HGA. We developed and implemented a functional assay and applied it to all 17 missense variants detected in a total of 26 CIC-deficient patients, including eight novel cases, showing reduced activities of varying degrees. In addition, we analyzed the importance of residues affected by these missense variants using our existing scoring system. This allowed not only a clinical and biochemical overview of the D/L-2-HGA patients but also phenotype-genotype correlation studies.

19.
PLoS One ; 12(10): e0186645, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29053735

RESUMO

Pyridoxine dependent epilepsy (PDE) is caused by likely pathogenic variants in ALDH7A1 (PDE-ALDH7A1) and inherited autosomal recessively. Neurotoxic alpha-amino adipic semialdehyde (alpha-AASA), piperideine 6-carboxylate and pipecolic acid accumulate in body fluids. Neonatal or infantile onset seizures refractory to anti-epileptic medications are clinical features. Treatment with pyridoxine, arginine and lysine-restricted diet does not normalize neurodevelopmental outcome or accumulation of neurotoxic metabolites. There is no animal model for high throughput drug screening. For this reason, we developed and characterized the first knock-out aldh7a1 zebrafish model using CRISPR-Cas9 technology. Zebrafish aldh7a1 mutants were generated by using a vector free method of CRISPR-Cas9 mutagenesis. Genotype analysis of aldh7a1 knock-out zebrafish was performed by high resolution melt analysis, direct sequencing and QIAxcel system. Electroencephalogram was performed. Alpha-AASA, piperideine 6-carboxylate and pipecolic acid, were measured by liquid chromatography-tandem mass spectrometry. Our knock-out aldh7a1 zebrafish has homozygous 5 base pair (bp) mutation in ALDH7A1. Knock-out aldh7a1 embryos have spontaneous rapid increase in locomotion and a rapid circling swim behavior earliest 8-day post fertilization (dpf). Electroencephalogram revealed large amplitude spike discharges compared to wild type. Knock-out aldh7a1 embryos have elevated alpha-AASA, piperideine 6-carboxylate and pipecolic acid compared to wild type embryos at 3 dpf. Knock-out aldh7a1 embryos showed no aldh7a1 protein by western blot compared to wild type. Our knock-out aldh7a1 zebrafish is a well characterized model for large-scale drug screening using behavioral and biochemical features and accurately recapitulates the human PDE-ALDH7A1 disease.


Assuntos
Aldeído Desidrogenase/genética , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas , Epilepsia/induzido quimicamente , Piridoxina/toxicidade , Peixe-Zebra/genética , Potenciais de Ação , Animais , Comportamento Animal , Eletroencefalografia , Epilepsia/genética , Epilepsia/fisiopatologia , Técnicas de Silenciamento de Genes , Peixe-Zebra/embriologia
20.
PLoS One ; 12(10): e0186919, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29053743

RESUMO

We explored the utility of neural stem cells (NSCs) as an in vitro model for evaluating preclinical therapeutics in succinic semialdehyde dehydrogenase-deficient (SSADHD) mice. NSCs were obtained from aldh5a1+/+ and aldh5a1-/- mice (aldh5a1 = aldehyde dehydrogenase 5a1 = SSADH). Multiple parameters were evaluated including: (1) production of GHB (γ-hydroxybutyrate), the biochemical hallmark of SSADHD; (2) rescue from cell death with the dual mTOR (mechanistic target of rapamycin) inhibitor, XL-765, an agent previously shown to rescue aldh5a1-/- mice from premature lethality; (3) mitochondrial number, total reactive oxygen species, and mitochondrial superoxide production, all previously documented as abnormal in aldh5a1-/- mice; (4) total ATP levels and ATP consumption; and (5) selected gene expression profiles associated with epilepsy, a prominent feature in both experimental and human SSADHD. Patterns of dysfunction were observed in all of these parameters and mirrored earlier findings in aldh5a1-/- mice. Patterns of dysregulated gene expression between hypothalamus and NSCs centered on ion channels, GABAergic receptors, and inflammation, suggesting novel pathomechanisms as well as a developmental ontogeny for gene expression potentially associated with the murine epileptic phenotype. The NSC model of SSADHD will be valuable in providing a first-tier screen for centrally-acting therapeutics and prioritizing therapeutic concepts of preclinical animal studies applicable to SSADHD.


Assuntos
Erros Inatos do Metabolismo dos Aminoácidos/patologia , Encéfalo/patologia , Deficiências do Desenvolvimento/patologia , Modelos Animais de Doenças , Células-Tronco Neurais/patologia , Succinato-Semialdeído Desidrogenase/deficiência , Trifosfato de Adenosina/metabolismo , Animais , Meios de Cultura , Epilepsia/genética , Técnicas In Vitro , Camundongos , Estresse Oxidativo , Succinato-Semialdeído Desidrogenase/genética
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