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1.
Can J Neurol Sci ; 46(6): 717-726, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31387656

RESUMO

BACKGROUND: An improved understanding of diagnostic and treatment practices for patients with rare primary mitochondrial disorders can support benchmarking against guidelines and establish priorities for evaluative research. We aimed to describe physician care for patients with mitochondrial diseases in Canada, including variation in care. METHODS: We conducted a cross-sectional survey of Canadian physicians involved in the diagnosis and/or ongoing care of patients with mitochondrial diseases. We used snowball sampling to identify potentially eligible participants, who were contacted by mail up to five times and invited to complete a questionnaire by mail or internet. The questionnaire addressed: personal experience in providing care for mitochondrial disorders; diagnostic and treatment practices; challenges in accessing tests or treatments; and views regarding research priorities. RESULTS: We received 58 survey responses (52% response rate). Most respondents (83%) reported spending 20% or less of their clinical practice time caring for patients with mitochondrial disorders. We identified important variation in diagnostic care, although assessments frequently reported as diagnostically helpful (e.g., brain magnetic resonance imaging, MRI/MR spectroscopy) were also recommended in published guidelines. Approximately half (49%) of participants would recommend "mitochondrial cocktails" for all or most patients, but we identified variation in responses regarding specific vitamins and cofactors. A majority of physicians recommended studies on the development of effective therapies as the top research priority. CONCLUSIONS: While Canadian physicians' views about diagnostic care and disease management are aligned with published recommendations, important variations in care reflect persistent areas of uncertainty and a need for empirical evidence to support and update standard protocols.

2.
Biol Psychiatry ; 2019 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-31443933

RESUMO

BACKGROUND: The X-chromosome gene USP9X encodes a deubiquitylating enzyme that has been associated with neurodevelopmental disorders primarily in female subjects. USP9X escapes X inactivation, and in female subjects de novo heterozygous copy number loss or truncating mutations cause haploinsufficiency culminating in a recognizable syndrome with intellectual disability and signature brain and congenital abnormalities. In contrast, the involvement of USP9X in male neurodevelopmental disorders remains tentative. METHODS: We used clinically recommended guidelines to collect and interrogate the pathogenicity of 44 USP9X variants associated with neurodevelopmental disorders in males. Functional studies in patient-derived cell lines and mice were used to determine mechanisms of pathology. RESULTS: Twelve missense variants showed strong evidence of pathogenicity. We define a characteristic phenotype of the central nervous system (white matter disturbances, thin corpus callosum, and widened ventricles); global delay with significant alteration of speech, language, and behavior; hypotonia; joint hypermobility; visual system defects; and other common congenital and dysmorphic features. Comparison of in silico and phenotypical features align additional variants of unknown significance with likely pathogenicity. In support of partial loss-of-function mechanisms, using patient-derived cell lines, we show loss of only specific USP9X substrates that regulate neurodevelopmental signaling pathways and a united defect in transforming growth factor ß signaling. In addition, we find correlates of the male phenotype in Usp9x brain-specific knockout mice, and further resolve loss of hippocampal-dependent learning and memory. CONCLUSIONS: Our data demonstrate the involvement of USP9X variants in a distinctive neurodevelopmental and behavioral syndrome in male subjects and identify plausible mechanisms of pathogenesis centered on disrupted transforming growth factor ß signaling and hippocampal function.

3.
Eur J Hum Genet ; 27(10): 1611-1618, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31278393

RESUMO

The developmental and epileptic encephalopathies (DEE) are a heterogeneous group of chronic encephalopathies frequently associated with rare de novo nonsynonymous coding variants in neuronally expressed genes. Here, we describe eight probands with a DEE phenotype comprising intellectual disability, epilepsy, and hypotonia. Exome trio analysis showed de novo variants in TRPM3, encoding a brain-expressed transient receptor potential channel, in each. Seven probands were identically heterozygous for a recurrent substitution, p.(Val837Met), in TRPM3's S4-S5 linker region, a conserved domain proposed to undergo conformational change during gated channel opening. The eighth individual was heterozygous for a proline substitution, p.(Pro937Gln), at the boundary between TRPM3's flexible pore-forming loop and an adjacent alpha-helix. General-population truncating variants and microdeletions occur throughout TRPM3, suggesting a pathomechanism other than simple haploinsufficiency. We conclude that de novo variants in TRPM3 are a cause of intellectual disability and epilepsy.

4.
Brain ; 142(3): 542-559, 2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30668673

RESUMO

Biallelic pathogenic variants in PLPBP (formerly called PROSC) have recently been shown to cause a novel form of vitamin B6-dependent epilepsy, the pathophysiological basis of which is poorly understood. When left untreated, the disease can progress to status epilepticus and death in infancy. Here we present 12 previously undescribed patients and six novel pathogenic variants in PLPBP. Suspected clinical diagnoses prior to identification of PLPBP variants included mitochondrial encephalopathy (two patients), folinic acid-responsive epilepsy (one patient) and a movement disorder compatible with AADC deficiency (one patient). The encoded protein, PLPHP is believed to be crucial for B6 homeostasis. We modelled the pathogenicity of the variants and developed a clinical severity scoring system. The most severe phenotypes were associated with variants leading to loss of function of PLPBP or significantly affecting protein stability/PLP-binding. To explore the pathophysiology of this disease further, we developed the first zebrafish model of PLPHP deficiency using CRISPR/Cas9. Our model recapitulates the disease, with plpbp-/- larvae showing behavioural, biochemical, and electrophysiological signs of seizure activity by 10 days post-fertilization and early death by 16 days post-fertilization. Treatment with pyridoxine significantly improved the epileptic phenotype and extended lifespan in plpbp-/- animals. Larvae had disruptions in amino acid metabolism as well as GABA and catecholamine biosynthesis, indicating impairment of PLP-dependent enzymatic activities. Using mass spectrometry, we observed significant B6 vitamer level changes in plpbp-/- zebrafish, patient fibroblasts and PLPHP-deficient HEK293 cells. Additional studies in human cells and yeast provide the first empirical evidence that PLPHP is localized in mitochondria and may play a role in mitochondrial metabolism. These models provide new insights into disease mechanisms and can serve as a platform for drug discovery.

5.
Can J Neurol Sci ; : 1-7, 2018 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-30419982

RESUMO

Multiple genes/variants have been implicated in various epileptic conditions. However, there is little general guidance available on the circumstances in which genetic testing is indicated and test selection in order to guide optimal test appropriateness and benefit. This is an account of the development of guidelines for genetic testing in epilepsy, which have been developed in Ontario, Canada. The Genetic Testing Advisory Committee was established in Ontario to review the clinical utility and validity of genetic tests and the provision of genetic testing in Ontario. As part of their mandate, the committee also developed recommendations and guidelines for genetic testing in epilepsy. The recommendations include mandatory prerequisites for an epileptology/geneticist/clinical biochemical geneticist consultation, prerequisite diagnostic procedures, circumstances in which genetic testing is indicated and not indicated and guidance for selection of genetic tests, including their general limitations and considerations. These guidelines represent a step toward the development of evidence-based gene panels for epilepsy in Ontario, the repatriation of genetic testing for epilepsy into Ontario molecular genetic laboratories and public funding of genetic tests for epilepsy in Ontario.

6.
Am J Med Genet A ; 2018 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-30244534

RESUMO

De novo mutations of the TRIM8 gene, which codes for a tripartite motif protein, have been identified using whole exome sequencing (WES) in two patients with epileptic encephalopathy (EE), but these reports were not sufficient to conclude that TRIM8 was a novel gene responsible for EE. Here we report four additional patients presenting with EE and de novo truncating mutations of TRIM8 detected by WES, and give further details of the patient previously reported by the Epi4K consortium. Epilepsy of variable severity was diagnosed in children aged 2 months to 3.5 years of age. All patients had developmental delay of variable severity with no or very limited language, often associated with behavioral anomalies and unspecific facial features or MRI brain abnormalities. The phenotypic variability observed in these patients appeared related to the severity of the epilepsy. One patient presented pharmacoresistant EE with regression, recurrent infections and nephrotic syndrome, compatible with the brain and kidney expression of TRIM8. Interestingly, all mutations were located at the highly conserved C-terminus section of TRIM8. This collaborative study confirms that TRIM8 is a novel gene responsible for EE, possibly associated with nephrotic syndrome. This report brings new evidence on the pathogenicity of TRIM8 mutations and highlights the value of data-sharing to delineate the phenotypic characteristics and biological basis of extremely rare disorders.

7.
Mol Genet Metab ; 125(3): 281-291, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30177229

RESUMO

An increasing number of mitochondrial diseases are found to be caused by pathogenic variants in nuclear encoded mitochondrial aminoacyl-tRNA synthetases. FARS2 encodes mitochondrial phenylalanyl-tRNA synthetase (mtPheRS) which transfers phenylalanine to its cognate tRNA in mitochondria. Since the first case was reported in 2012, a total of 21 subjects with FARS2 deficiency have been reported to date with a spectrum of disease severity that falls between two phenotypes; early onset epileptic encephalopathy and a less severe phenotype characterized by spastic paraplegia. In this report, we present an additional 15 individuals from 12 families who are mostly Arabs homozygous for the pathogenic variant Y144C, which is associated with the more severe early onset phenotype. The total number of unique pathogenic FARS2 variants known to date is 21 including three different partial gene deletions reported in four individuals. Except for the large deletions, all variants but two (one in-frame deletion of one amino acid and one splice-site variant) are missense. All large deletions and the single splice-site variant are in trans with a missense variant. This suggests that complete loss of function may be incompatible with life. In this report, we also review structural, functional, and evolutionary significance of select FARS2 pathogenic variants reported here.

9.
Mol Genet Metab ; 123(3): 309-316, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29269105

RESUMO

Serine biosynthesis defects are autosomal recessive metabolic disorders resulting from the deficiency of any of the three enzymes involved in de novo serine biosynthesis, specifically phosphoglycerate dehydrogenase (PGDH), phosphoserine aminotransferase (PSAT), and phosphoserine phosphatase (PSP). In this study, we performed metabolomic profiling on 4 children with serine biosynthesis defects; 3 with PGDH deficiency and 1 with PSAT deficiency. The evaluations were performed at baseline and with serine and glycine supplementation. Metabolomic profiling performed at baseline showed low phospholipid species, including glycerophosphocholine, glycerophosphoethanolamine, and sphingomyelin. All children had low serine and glycine as expected. Low glycerophosphocholine compounds were found in 4 children, low glycerophosphoethanolamine compounds in 3 children, and low sphingomyelin species in 2 children. Metabolic profiling with serine and glycine supplementation showed normalization of most of the low phospholipid compounds in the 4 children. Phospholipids are the major component of plasma and intracellular membranes, and phosphatidylcholine is the most abundant phospholipid of all mammalian cell types and subcellular organelles. Phosphatidylcholine is of particular importance for the nervous system, where it is essential for neuronal differentiation. The observed low phosphatidylcholine species in children with serine biosynthesis defects that improved after serine supplementation, supports the role of serine as a significant precursor for phosphatidylcholine. The vital role that phosphatidylcholine has during neuronal differentiation and the pronounced neurological manifestations in serine biosynthesis defects suggest that phosphatidylcholine deficiency occurring secondary to serine deficiency may have a significant contribution to the development of the neurological manifestations in individuals with serine biosynthesis defects.

10.
Am J Med Genet B Neuropsychiatr Genet ; 177(1): 101-109, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29152901

RESUMO

White matter lesions have been described in patients with PTEN hamartoma tumor syndrome (PHTS). How these lesions correlate with the neurocognitive features associated with PTEN mutations, such as autism spectrum disorder (ASD) or developmental delay, has not been well established. We report nine patients with PTEN mutations and white matter changes on brain magnetic resonance imaging (MRI), eight of whom were referred for reasons other than developmental delay or ASD. Their clinical presentations ranged from asymptomatic macrocephaly with normal development/intellect, to obsessive compulsive disorder, and debilitating neurological disease. To our knowledge, this report constitutes the first detailed description of PTEN-related white matter changes in adult patients and in children with normal development and intelligence. We present a detailed assessment of the neuropsychological phenotype of our patients and discuss the relationship between the wide array of neuropsychiatric features and observed white matter findings in the context of these individuals.


Assuntos
Síndrome do Hamartoma Múltiplo/fisiopatologia , Leucoencefalopatias/metabolismo , PTEN Fosfo-Hidrolase/metabolismo , Adolescente , Adulto , Transtorno do Espectro Autista/genética , Criança , Pré-Escolar , Deficiências do Desenvolvimento , Feminino , Síndrome do Hamartoma Múltiplo/genética , Humanos , Inteligência , Leucoencefalopatias/genética , Imagem por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Fenótipo , Substância Branca/patologia
11.
Eur J Hum Genet ; 25(9): 1049-1054, 2017 09.
Artigo em Inglês | MEDLINE | ID: mdl-28635952

RESUMO

Yunis-Varón syndrome (YVS) is an autosomal recessive disorder comprising skeletal anomalies, dysmorphism, global developmental delay and intracytoplasmic vacuolation in brain and other tissues. All hitherto-reported pathogenic variants affect FIG4, a lipid phosphatase involved in phosphatidylinositol (3,5)-bisphosphate [PtdIns(3,5)P2] metabolism. FIG4 interacts with PIKfyve, a lipid kinase, via the adapter protein VAC14; all subunits of the resulting complex are essential for PtdIns(3,5)P2 synthesis in the endolysosomal membrane compartment. Here, we present the case of a female neonate with clinical features of YVS and normal FIG4 sequencing; exome sequencing identified biallelic rare coding variants in VAC14. Cultured patient fibroblasts exhibited a YVS-like vacuolation phenotype ameliorated in a dose-dependent fashion by ML-SA1, a pharmacological activator of the lysosomal PtdIns(3,5)P2 effector TRPML1. The patient developed a diffuse leukoencephalopathy with loss of the normal N-acetylaspartate spectrographic peak and presence of a large abnormal peak consistent with myoinositol. We report that VAC14 is a second gene for Yunis-Varón syndrome.


Assuntos
Displasia Cleidocraniana/genética , Displasia Ectodérmica/genética , Deformidades Congênitas dos Membros/genética , Proteínas de Membrana/genética , Micrognatismo/genética , Mutação , Alelos , Células Cultivadas , Displasia Cleidocraniana/diagnóstico , Displasia Ectodérmica/diagnóstico , Feminino , Fibroblastos/citologia , Fibroblastos/efeitos dos fármacos , Fibroblastos/metabolismo , Humanos , Recém-Nascido , Inositol/metabolismo , Deformidades Congênitas dos Membros/diagnóstico , Proteínas de Membrana/metabolismo , Micrognatismo/diagnóstico , Fenótipo , Ftalimidas/farmacologia , Quinolinas/farmacologia , Vacúolos/metabolismo
12.
Orphanet J Rare Dis ; 12(1): 121, 2017 06 28.
Artigo em Inglês | MEDLINE | ID: mdl-28659154

RESUMO

BACKGROUND: Spinocerebellar ataxia type 29 (SCA29) is an autosomal dominant, non-progressive cerebellar ataxia characterized by infantile-onset hypotonia, gross motor delay and cognitive impairment. Affected individuals exhibit cerebellar dysfunction and often have cerebellar atrophy on neuroimaging. Recently, missense mutations in ITPR1 were determined to be responsible. RESULTS: Clinical information on 21 individuals from 15 unrelated families with ITPR1 mutations was retrospectively collected using standardized questionnaires, including 11 previously unreported singletons and 2 new patients from a previously reported family. We describe the genetic, clinical and neuroimaging features of these patients to further characterize the clinical features of this rare condition and assess for any genotype-phenotype correlation for this disorder. Our cohort consisted of 9 males and 12 females, with ages ranging from 28 months to 49 years. Disease course was non-progressive with infantile-onset hypotonia and delays in motor and speech development. Gait ataxia was present in all individuals and 10 (48%) were not ambulating independently between the ages of 3-12 years of age. Mild-to-moderate cognitive impairment was present in 17 individuals (85%). Cerebellar atrophy developed after initial symptom presentation in 13 individuals (72%) and was not associated with disease progression or worsening functional impairment. We identified 12 different mutations including 6 novel mutations; 10 mutations were missense (with 4 present in >1 individual), 1 a splice site mutation leading to an in-frame insertion and 1 an in-frame deletion. No specific genotype-phenotype correlations were observed within our cohort. CONCLUSIONS: Our findings document significant clinical heterogeneity between individuals with SCA29 in a large cohort of molecularly confirmed cases. Based on the retrospective observed clinical features and disease course, we provide recommendations for management. Further research into the natural history of SCA29 through prospective studies is an important next step in better understanding the condition.


Assuntos
Receptores de Inositol 1,4,5-Trifosfato/genética , Ataxias Espinocerebelares/genética , Adolescente , Adulto , Ataxia Cerebelar/genética , Criança , Pré-Escolar , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Mutação/genética , Estudos Retrospectivos , Adulto Jovem
13.
Neuropediatrics ; 48(3): 166-184, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28561207

RESUMO

We investigated the genetic, phenotypic, and interferon status of 46 patients from 37 families with neurological disease due to mutations in ADAR1. The clinicoradiological phenotype encompassed a spectrum of Aicardi-Goutières syndrome, isolated bilateral striatal necrosis, spastic paraparesis with normal neuroimaging, a progressive spastic dystonic motor disorder, and adult-onset psychological difficulties with intracranial calcification. Homozygous missense mutations were recorded in five families. We observed a p.Pro193Ala variant in the heterozygous state in 22 of 23 families with compound heterozygous mutations. We also ascertained 11 cases from nine families with a p.Gly1007Arg dominant-negative mutation, which occurred de novo in four patients, and was inherited in three families in association with marked phenotypic variability. In 50 of 52 samples from 34 patients, we identified a marked upregulation of type I interferon-stimulated gene transcripts in peripheral blood, with a median interferon score of 16.99 (interquartile range [IQR]: 10.64-25.71) compared with controls (median: 0.93, IQR: 0.57-1.30). Thus, mutations in ADAR1 are associated with a variety of clinically distinct neurological phenotypes presenting from early infancy to adulthood, inherited either as an autosomal recessive or dominant trait. Testing for an interferon signature in blood represents a useful biomarker in this context.


Assuntos
Adenosina Desaminase/genética , Doenças Autoimunes do Sistema Nervoso/genética , Doenças Autoimunes do Sistema Nervoso/imunologia , Interferon Tipo I/metabolismo , Malformações do Sistema Nervoso/genética , Malformações do Sistema Nervoso/imunologia , Proteínas de Ligação a RNA/genética , Adolescente , Adulto , Doenças Autoimunes do Sistema Nervoso/diagnóstico por imagem , Biomarcadores/metabolismo , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Masculino , Mutação , Malformações do Sistema Nervoso/diagnóstico por imagem , Fenótipo , Adulto Jovem
14.
CMAJ ; 188(11): E254-60, 2016 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-27241786

RESUMO

BACKGROUND: Rare diseases often present in the first days and weeks of life and may require complex management in the setting of a neonatal intensive care unit (NICU). Exhaustive consultations and traditional genetic or metabolic investigations are costly and often fail to arrive at a final diagnosis when no recognizable syndrome is suspected. For this pilot project, we assessed the feasibility of next-generation sequencing as a tool to improve the diagnosis of rare diseases in newborns in the NICU. METHODS: We retrospectively identified and prospectively recruited newborns and infants admitted to the NICU of the Children's Hospital of Eastern Ontario and the Ottawa Hospital, General Campus, who had been referred to the medical genetics or metabolics inpatient consult service and had features suggesting an underlying genetic or metabolic condition. DNA from the newborns and parents was enriched for a panel of clinically relevant genes and sequenced on a MiSeq sequencing platform (Illumina Inc.). The data were interpreted with a standard informatics pipeline and reported to care providers, who assessed the importance of genotype-phenotype correlations. RESULTS: Of 20 newborns studied, 8 received a diagnosis on the basis of next-generation sequencing (diagnostic rate 40%). The diagnoses were renal tubular dysgenesis, SCN1A-related encephalopathy syndrome, myotubular myopathy, FTO deficiency syndrome, cranioectodermal dysplasia, congenital myasthenic syndrome, autosomal dominant intellectual disability syndrome type 7 and Denys-Drash syndrome. INTERPRETATION: This pilot study highlighted the potential of next-generation sequencing to deliver molecular diagnoses rapidly with a high success rate. With broader use, this approach has the potential to alter health care delivery in the NICU.


Assuntos
Estudos de Associação Genética/métodos , Testes Genéticos/métodos , Sequenciamento de Nucleotídeos em Larga Escala , Unidades de Terapia Intensiva Neonatal , Doenças Raras/diagnóstico , Doenças Raras/genética , Feminino , Humanos , Recém-Nascido , Masculino , Mutação , Ontário , Projetos Piloto , Estudos Prospectivos , Estudos Retrospectivos
15.
JIMD Rep ; 30: 73-79, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27306203

RESUMO

Mutations of the mitochondrial citrate carrier (CIC) SLC25A1 cause combined D-2- and L-2-hydroxyglutaric aciduria (DL-2HGA; OMIM #615182), a neurometabolic disorder characterized by developmental delay, hypotonia, and seizures. Here, we describe the female child of consanguineous parents who presented neonatally with lactic acidosis, periventricular frontal lobe cysts, facial dysmorphism, recurrent apneic episodes, and deficient complex IV (cytochrome c oxidase) activity in skeletal muscle. Exome sequencing revealed a homozygous SLC25A1 missense mutation [NM_005984.4: c.593G>A; p.(Arg198His)] of a ubiquitously conserved arginine residue putatively situated within the substrate-binding site I of CIC. Retrospective review of the patient's organic acids confirmed the D- and L-2-hydroxyglutaric aciduria typical of DL-2HGA to be present, although this was not appreciated on initial presentation. Cultured patient skin fibroblasts showed reduced survival in culture, diminished mitochondrial spare respiratory capacity, increased glycolytic flux, and normal mitochondrial bulk, inner membrane potential, and network morphology. Neither cell survival nor cellular respiratory parameters were improved by citrate supplementation, although oral citrate supplementation did coincide with amelioration of lactic acidosis and apneic attacks in the patient. This is the fifth clinical report of CIC deficiency to date. The clinical features in our patient suggest that this disorder, which can potentially be recognized either by molecular means or based on its characteristic organic aciduria, should be considered in the differential diagnosis of pyruvate dehydrogenase deficiency and respiratory chain disorders. One-Sentence Summary A novel homozygous missense substitution in SLC25A1 was identified in a neonate presenting with lactic acidosis, intracerebral cysts, and an apparent mitochondrial complex IV defect in muscle.

16.
Orphanet J Rare Dis ; 11(1): 79, 2016 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-27317422

RESUMO

BACKGROUND: SIFD (Sideroblastic anemia with B-cell immunodeficiency, periodic fevers, and developmental delay) is a novel form of congenital sideroblastic anemia associated with B-cell immunodeficiency, periodic fevers, and developmental delay caused by mutations in the CCA-adding enzyme TRNT1, but the precise molecular pathophysiology is not known. RESULTS: We show that the disease causing mutations in patient-derived fibroblasts do not affect subcellular localization of TRNT1 and show no gross morphological differences when compared to control cells. Analysis of cellular respiration and oxidative phosphorylation (OXPHOS) complexes demonstrates that both basal and maximal respiration rates are decreased in patient cells, which may be attributed to an observed decrease in the abundance of select proteins of the OXPHOS complexes. CONCLUSIONS: Our data provides further insight into cellular pathophysiology of SIFD.


Assuntos
Anemia Sideroblástica/metabolismo , Respiração Celular/fisiologia , Fibroblastos/metabolismo , Nucleotidiltransferases/metabolismo , Anemia Sideroblástica/genética , Western Blotting , Respiração Celular/genética , Células Cultivadas , Feminino , Imunofluorescência , Humanos , Potencial da Membrana Mitocondrial , Microscopia Eletrônica de Transmissão , Mitocôndrias/metabolismo , Mutação , Nucleotidiltransferases/genética , Fosforilação Oxidativa
17.
Eur J Hum Genet ; 24(7): 1084-8, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-26604000

RESUMO

Mitochondrial fission and fusion are dynamic processes vital to mitochondrial quality control and the maintenance of cellular respiration. In dividing mitochondria, membrane scission is accomplished by a dynamin-related GTPase, DNM1L, that oligomerizes at the site of fission and constricts in a GTP-dependent manner. There is only a single previous report of DNM1L-related clinical disease: a female neonate with encephalopathy due to defective mitochondrial and peroxisomal fission (EMPF; OMIM #614388), a lethal disorder characterized by cerebral dysgenesis, seizures, lactic acidosis, elevated very long chain fatty acids, and abnormally elongated mitochondria and peroxisomes. Here, we describe a second individual, diagnosed via whole-exome sequencing, who presented with developmental delay, refractory epilepsy, prolonged survival, and no evidence of mitochondrial or peroxisomal dysfunction on standard screening investigations in blood and urine. EEG was nonspecific, showing background slowing with frequent epileptiform activity at the frontal and central head regions. Electron microscopy of skeletal muscle showed subtle, nonspecific abnormalities of cristal organization, and confocal microscopy of patient fibroblasts showed striking hyperfusion of the mitochondrial network. A panel of further bioenergetic studies in patient fibroblasts showed no significant differences versus controls. The proband's de novo DNM1L variant, NM_012062.4:c.1085G>A; NP_036192.2:p.(Gly362Asp), falls within the middle (oligomerization) domain of DNM1L, implying a likely dominant-negative mechanism. This disorder, which presents nonspecifically and affords few diagnostic clues, can be diagnosed by means of DNM1L sequencing and/or confocal microscopy.


Assuntos
Deficiências do Desenvolvimento/genética , Epilepsia Resistente a Medicamentos/genética , GTP Fosfo-Hidrolases/genética , Proteínas Associadas aos Microtúbulos/genética , Dinâmica Mitocondrial/genética , Proteínas Mitocondriais/genética , Mutação de Sentido Incorreto , Células Cultivadas , Criança , Deficiências do Desenvolvimento/patologia , Epilepsia Resistente a Medicamentos/patologia , Exoma , Fibroblastos/ultraestrutura , Humanos , Masculino , Mitocôndrias Musculares/metabolismo , Mitocôndrias Musculares/ultraestrutura , Músculo Esquelético/ultraestrutura , Síndrome
18.
JIMD Rep ; 27: 1-9, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26404457

RESUMO

Mutations of FBXL4, which encodes an orphan mitochondrial F-box protein, are a recently identified cause of encephalomyopathic mtDNA depletion. Here, we describe the detailed clinical and biochemical phenotype of a neonate presenting with hyperlactatemia, leukoencephalopathy, arrhythmias, pulmonary hypertension, dysmorphic features, and lymphopenia. Next-generation sequencing in the proband identified a homozygous frameshift, c.1641_1642delTG, in FBXL4, with a surrounding block of SNP marker homozygosity identified by microarray. Muscle biopsy showed a paucity of mitochondria with ultrastructural abnormalities, mitochondrial DNA depletion, and profound deficiency of all respiratory chain complexes. Cell-based mitochondrial phenotyping in fibroblasts showed mitochondrial fragmentation, decreased basal and maximal respiration, absence of ATP-linked respiratory and leak capacity, impaired survival under obligate aerobic respiration, and reduced mitochondrial inner membrane potential, with relative sparing of mitochondrial mass. Cultured fibroblasts from the patient exhibited a more oxidized glutathione ratio, consistent with altered cellular redox poise. High-resolution respirometry of permeabilized muscle fibers showed marked deficiency of oxidative phosphorylation using a variety of mitochondrial energy substrates and inhibitors. This constitutes the fourth and most detailed report of FBXL4 deficiency to date. In light of our patient's clinical findings and genotype (homozygous frameshift), this phenotype likely represents the severe end of the FBXL4 clinical spectrum.

19.
Am J Med Genet A ; 170A(4): 967-77, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26692240

RESUMO

We report 13 new individuals with duplications in Xp11.22-p11.23. The index family has one male and two female members in three generations with mild-severe intellectual disability (ID), speech delay, dysmorphic features, early puberty, constipation, and/or hand and foot abnormalities. Affected individuals were found to have two small duplications in Xp11.22 at nucleotide position (hg19) 50,112,063-50,456,458 bp (distal) and 53,160,114-53,713,154 bp (proximal). Collectively, these two regions include 14 RefSeq genes, prompting collection of a larger cohort of patients, in an attempt to delineate critical genes associated with the observed phenotype. In total, we have collected data on nine individuals with duplications overlapping the distal duplication region containing SHROOM4 and DGKK and eight individuals overlapping the proximal region including HUWE1. Duplications of HUWE1 have been previously associated with non-syndromic ID. Our data, with previously published reports, suggest that duplications involving SHROOM4 and DGKK may represent a new syndromic X-linked ID critical region associated with mild to severe ID, speech delay +/- dysarthria, attention deficit disorder, precocious puberty, constipation, and motor delay. We frequently observed foot abnormalities, 5th finger clinodactyly, tapering fingers, constipation, and exercise intolerance in patients with duplications of these two genes. Regarding duplications including the proximal region, our observations agree with previous studies, which have found associations with intellectual disability. In addition, expressive language delay, failure to thrive, motor delay, and 5th finger clinodactyly were also frequently observed in patients with the proximal duplication.


Assuntos
Duplicação Cromossômica , Cromossomos Humanos X , Estudos de Associação Genética , Transtornos dos Cromossomos Sexuais/diagnóstico , Transtornos dos Cromossomos Sexuais/genética , Adolescente , Adulto , Idoso , Criança , Mapeamento Cromossômico , Hibridização Genômica Comparativa , Facies , Feminino , Genótipo , Humanos , Masculino , Pessoa de Meia-Idade , Linhagem , Fenótipo , Adulto Jovem
20.
Hum Genet ; 134(9): 981-91, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26099313

RESUMO

Leigh syndrome (LS) is a rare heterogeneous progressive neurodegenerative disorder usually presenting in infancy or early childhood. Clinical presentation is variable and includes psychomotor delay or regression, acute neurological or acidotic episodes, hypotonia, ataxia, spasticity, movement disorders, and corresponding anomalies of the basal ganglia and brain stem on magnetic resonance imaging. To date, 35 genes have been associated with LS, mostly involved in mitochondrial respiratory chain function and encoded in either nuclear or mitochondrial DNA. We used whole-exome sequencing to identify disease-causing variants in four patients with basal ganglia abnormalities and clinical presentations consistent with LS. Compound heterozygote variants in ECHS1, encoding the enzyme enoyl-CoA hydratase were identified. One missense variant (p.Thr180Ala) was common to all four patients and the haplotype surrounding this variant was also shared, suggesting a common ancestor of French-Canadian origin. Rare mutations in ECHS1 as well as in HIBCH, the enzyme downstream in the valine degradation pathway, have been associated with LS or LS-like disorders. A clear clinical overlap is observed between our patients and the reported cases with ECHS1 or HIBCH deficiency. The main clinical features observed in our cohort are T2-hyperintense signal in the globus pallidus and putamen, failure to thrive, developmental delay or regression, and nystagmus. Respiratory chain studies are not strikingly abnormal in our patients: one patient had a mild reduction of complex I and III and another of complex IV. The identification of four additional patients with mutations in ECHS1 highlights the emerging importance of this pathway in LS.


Assuntos
Enoil-CoA Hidratase/genética , Exoma , Doença de Leigh/genética , Anormalidades Múltiplas/sangue , Erros Inatos do Metabolismo dos Aminoácidos/sangue , Canadá , Pré-Escolar , Análise Mutacional de DNA , Feminino , Haplótipos , Heterozigoto , Humanos , Lactente , Doença de Leigh/diagnóstico , Imagem por Ressonância Magnética , Masculino , Mutação , Linhagem , Tioléster Hidrolases/sangue , Tioléster Hidrolases/deficiência
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