RESUMEN
Mitochondria are multifaceted organelles crucial for cellular homeostasis that contain their own genome. Mitochondrial DNA (mtDNA) replication is a spatially regulated process essential for the maintenance of mitochondrial function, its defect causing mitochondrial diseases. mtDNA replication occurs at endoplasmic reticulum (ER)-mitochondria contact sites and is affected by mitochondrial dynamics: The absence of mitochondrial fusion is associated with mtDNA depletion whereas loss of mitochondrial fission causes the aggregation of mtDNA within abnormal structures termed mitobulbs. Here, we show that contact sites between mitochondria and ER sheets, the ER structure associated with protein synthesis, regulate mtDNA replication and distribution within mitochondrial networks. DRP1 loss or mutation leads to modified ER sheets and alters the interaction between ER sheets and mitochondria, disrupting RRBP1-SYNJ2BP interaction. Importantly, mtDNA distribution and replication were rescued by promoting ER sheets-mitochondria contact sites. Our work identifies the role of ER sheet-mitochondria contact sites in regulating mtDNA replication and distribution.
RESUMEN
TRPM3 encodes a transient receptor potential cation channel of the melastatin family, expressed in the central nervous system and in peripheral sensory neurons of the dorsal root ganglia. The recurrent substitution in TRPM3: c.2509G>A, p.(Val837Met) has been associated with syndromic intellectual disability and seizures. In this report, we present the clinical and molecular features of seven previously unreported individuals, identified by exome sequencing, with the recurrent p.(Val837Met) variant and global developmental delay. Other shared clinical features included congenital hypotonia, dysmorphic facial features (broad forehead, deep-set eyes, and down turned mouth), exotropia, and musculoskeletal issues (hip dysplasia, hip dislocation, scoliosis). Seizures were observed in two of seven individuals (febrile seizure in one and generalized tonic-clonic seizures with atonic drops in another), and epileptiform activity was observed in an additional two individuals. This report extends the number of affected individuals to 16 who are heterozygous for the de novo recurrent substitution p.(Val837Met). In contrast with the initial report, epilepsy was not a mandatory feature observed in this series. TRPM3 pathogenic variation should be considered in individuals with global developmental delays, moderate-severe intellectual disability with, or without, childhood-onset epilepsy.
Asunto(s)
Epilepsia , Enfermedades del Recién Nacido , Discapacidad Intelectual , Canales Catiónicos TRPM , Niño , Discapacidades del Desarrollo/genética , Humanos , Recién Nacido , Discapacidad Intelectual/genética , Hipotonía Muscular/genética , Mutación Missense , Canales Catiónicos TRPM/genética , Secuenciación del ExomaRESUMEN
Developmental and epileptic encephalopathy 35 (DEE 35) is a severe neurological condition caused by biallelic variants in ITPA, encoding inosine triphosphate pyrophosphatase, an essential enzyme in purine metabolism. We delineate the genotypic and phenotypic spectrum of DEE 35, analyzing possible predictors for adverse clinical outcomes. We investigated a cohort of 28 new patients and reviewed previously described cases, providing a comprehensive characterization of 40 subjects. Exome sequencing was performed to identify underlying ITPA pathogenic variants. Brain MRI (magnetic resonance imaging) scans were systematically analyzed to delineate the neuroradiological spectrum. Survival curves according to the Kaplan-Meier method and log-rank test were used to investigate outcome predictors in different subgroups of patients. We identified 18 distinct ITPA pathogenic variants, including 14 novel variants, and two deletions. All subjects showed profound developmental delay, microcephaly, and refractory epilepsy followed by neurodevelopmental regression. Brain MRI revision revealed a recurrent pattern of delayed myelination and restricted diffusion of early myelinating structures. Congenital microcephaly and cardiac involvement were statistically significant novel clinical predictors of adverse outcomes. We refined the molecular, clinical, and neuroradiological characterization of ITPase deficiency, and identified new clinical predictors which may have a potentially important impact on diagnosis, counseling, and follow-up of affected individuals.
Asunto(s)
Epilepsia Generalizada , Microcefalia , Pirofosfatasas , Humanos , Inosina , Inosina Trifosfato , Microcefalia/patología , Mutación , Pronóstico , Pirofosfatasas/genética , Inosina TrifosfatasaRESUMEN
Mitochondrial DNA (mtDNA) maintenance is essential to sustain a functionally healthy population of mitochondria within cells. Proper mtDNA replication and distribution within mitochondrial networks are essential to maintain mitochondrial homeostasis. However, the fundamental basis of mtDNA segregation and distribution within mitochondrial networks is still unclear. To address these questions, we developed an algorithm, Mitomate tracker to unravel the global distribution of nucleoids within mitochondria. Using this tool, we decipher the semi-regular spacing of nucleoids across mitochondrial networks. Furthermore, we show that mitochondrial fission actively regulates mtDNA distribution by controlling the distribution of nucleoids within mitochondrial networks. Specifically, we found that primary cells bearing disease-associated mutations in the fission proteins DRP1 and MYH14 show altered nucleoid distribution, and acute enrichment of enlarged nucleoids near the nucleus. Further analysis suggests that the altered nucleoid distribution observed in the fission mutants is the result of both changes in network structure and nucleoid density. Thus, our study provides novel insights into the role of mitochondria fission in nucleoid distribution and the understanding of diseases caused by fission defects.
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Núcleo Celular/metabolismo , ADN Mitocondrial/metabolismo , Dinaminas/metabolismo , Homeostasis , Mitocondrias/metabolismo , Dinámicas Mitocondriales , Cadenas Pesadas de Miosina/metabolismo , Miosina Tipo II/metabolismo , Núcleo Celular/genética , Replicación del ADN , ADN Mitocondrial/genética , Dinaminas/genética , Humanos , Mitocondrias/genética , Cadenas Pesadas de Miosina/genética , Miosina Tipo II/genéticaRESUMEN
Mitochondrial disorders are a heterogeneous group of rare, degenerative multisystem disorders affecting the cell's core bioenergetic and signalling functions. Spontaneous improvement is rare. We describe a novel neonatal-onset mitochondriopathy in three infants with failure to thrive, hyperlactatemia, hyperammonemia, and apparent clinical resolution before 18 months. Exome sequencing showed all three probands to be identically heterozygous for a recurrent de novo substitution, c.620G>A [p.(Arg207His)] in ATP5F1A, encoding the α-subunit of complex V. Patient-derived fibroblasts exhibited multiple deficits in complex V function and expression in vitro. Structural modelling predicts the observed substitution to create an abnormal region of negative charge on ATP5F1A's ß-subunit-interacting surface, adjacent to the nearby ß subunit's active site. This disorder, which presents with life-threatening neonatal manifestations, appears to follow a remitting course; the long-term prognosis remains unknown.
Asunto(s)
Enfermedades Mitocondriales/genética , ATPasas de Translocación de Protón Mitocondriales/metabolismo , Dominio Catalítico , Células Cultivadas , Preescolar , Femenino , Fibroblastos/metabolismo , Humanos , Lactante , Masculino , Enfermedades Mitocondriales/metabolismo , Enfermedades Mitocondriales/patología , ATPasas de Translocación de Protón Mitocondriales/química , ATPasas de Translocación de Protón Mitocondriales/genética , Mutación , FenotipoRESUMEN
Idiopathic ketotic hypoglycemia (IKH) is a diagnosis of exclusion with glycogen storage diseases (GSDs) as a differential diagnosis. GSD IXa presents with ketotic hypoglycemia (KH), hepatomegaly, and growth retardation due to PHKA2 variants. In our multicenter study, 12 children from eight families were diagnosed or suspected of IKH. Whole-exome sequencing or targeted next-generation sequencing panels were performed. We identified two known and three novel (likely) pathogenic PHKA2 variants, such as p.(Pro869Arg), p.(Pro498Leu), p.(Arg2Gly), p.(Arg860Trp), and p.(Val135Leu), respectively. Erythrocyte phosphorylase kinase activity in three patients with the novel variants p.(Arg2Gly) and p.(Arg860Trp) were 15%-20% of mean normal. One patient had short stature and intermittent mildly elevated aspartate aminotransferase, but no hepatomegaly. Family testing identified two asymptomatic children and 18 adult family members with one of the PHKA2 variants, of which 10 had KH symptoms in childhood and 8 had mild symptoms in adulthood. Our study expands the classical GSD IXa phenotype of PHKA2 missense variants to a continuum from seemingly asymptomatic carriers, over KH-only with phosphorylase B kinase deficiency, to more or less complete classical GSD IXa. In contrast to typical IKH, which is confined to young children, KH may persist into adulthood in the KH-only phenotype of PHKA2.
Asunto(s)
Enfermedad del Almacenamiento de Glucógeno/genética , Hepatomegalia/genética , Hipoglucemia/genética , Fosforilasa Quinasa/genética , Acidemia Propiónica/genética , Adolescente , Adulto , Niño , Preescolar , Diagnóstico Diferencial , Femenino , Enfermedad del Almacenamiento de Glucógeno/diagnóstico , Enfermedad del Almacenamiento de Glucógeno/patología , Hepatomegalia/diagnóstico , Hepatomegalia/patología , Secuenciación de Nucleótidos de Alto Rendimiento , Humanos , Hipoglucemia/diagnóstico , Hipoglucemia/patología , Masculino , Mutación Missense/genética , Linaje , Fenotipo , Acidemia Propiónica/diagnóstico , Acidemia Propiónica/epidemiología , Acidemia Propiónica/patología , Secuenciación del Exoma , Adulto JovenRESUMEN
EFTUD2 is mutated in patients with mandibulofacial dysostosis with microcephaly (MFDM). We generated a mutant mouse line with conditional mutation in Eftud2 and used Wnt1-Cre2 to delete it in neural crest cells. Homozygous deletion of Eftud2 causes brain and craniofacial malformations, affecting the same precursors as in MFDM patients. RNAseq analysis of embryonic heads revealed a significant increase in exon skipping and increased levels of an alternatively spliced Mdm2 transcript lacking exon 3. Exon skipping in Mdm2 was also increased in O9-1 mouse neural crest cells after siRNA knock-down of Eftud2 and in MFDM patient cells. Moreover, we found increased nuclear P53, higher expression of P53-target genes and increased cell death. Finally, overactivation of the P53 pathway in Eftud2 knockdown cells was attenuated by overexpression of non-spliced Mdm2, and craniofacial development was improved when Eftud2-mutant embryos were treated with Pifithrin-α, an inhibitor of P53. Thus, our work indicates that the P53-pathway can be targeted to prevent craniofacial abnormalities and shows a previously unknown role for alternative splicing of Mdm2 in the etiology of MFDM.
Asunto(s)
Ribonucleoproteína Nuclear Pequeña U5 , Proteína p53 Supresora de Tumor , Animales , Homocigoto , Humanos , Ratones , Mutación , Factores de Elongación de Péptidos/genética , Proteínas Proto-Oncogénicas c-mdm2/genética , Proteínas Proto-Oncogénicas c-mdm2/metabolismo , Ribonucleoproteína Nuclear Pequeña U5/genética , Eliminación de Secuencia , Proteína p53 Supresora de Tumor/genética , Proteína p53 Supresora de Tumor/metabolismoRESUMEN
BACKGROUND: Lactic acidosis is a common finding in neonates, in whom mitochondrial dysfunction is often secondary to tissue hypoperfusion, respiratory failure, and/or sepsis. Primary (non-physiological) lactic acidosis is comparatively rare, and suggests the presence of an inborn error of mitochondrial energy metabolism. Optimal medical management and accurate prognostication requires the correct determination of the etiology of lactic acidosis in a given patient. Unfortunately, genetic diagnoses are rare and highly variable for neonates presenting with primary lactic acidosis; individual case reports may offer the most promise for treatment considerations. The mitochondrion is a complex molecular machine incorporating the products of > 1000 distinct nuclear genes. Primary lactic acidoses are therefore characterized by high genetic heterogeneity and a specific genetic diagnosis currently remains out of reach in most cases. Most mitochondriopathies with neonatal onset follow autosomal recessive inheritance and carry a poor prognosis. Here we detail the case of a father and daughter with dominantly-inherited, resolving (i.e. transient) neonatal hyperlactatemia due to complex IV deficiency. We found no other published descriptions of benign transient complex IV deficiency with autosomal dominant inheritance. CASE PRESENTATION: Both individuals presented as neonates with unexplained, marked lactic acidosis suggesting a primary mitochondrial disorder. Within the first weeks of life, elevated blood lactate levels normalized. Their clinical and developmental outcomes were normal. Biochemical studies in the proband showed multiple abnormalities consistent with a complex IV respiratory chain defect. Cultured skin fibroblasts showed an elevated lactate-to-pyruvate ratio, deficient complex IV activity, and normal pyruvate dehydrogenase and pyruvate carboxylase activities. Whole-exome sequencing of the proband and both parents did not identify a causative mutation. CONCLUSION: We conclude that the proband and her father appear to have a dominant form of transient neonatal hyperlactatemia due to heterozygous changes in an as-yet unidentified gene. This transient neonatal complex IV deficiency should be considered in the differential diagnosis of primary neonatal hyperlactatemia; notable clinical features include autosomal-dominant inheritance and an apparently benign postnatal course. This report exemplifies the growing differential diagnosis for neonatal lactic acidosis and highlights the importance of both physician counselling and the use of family history in communicating with parents.
Asunto(s)
Acidosis Láctica , Acidosis , Enfermedades del Recién Nacido , Enfermedades Mitocondriales , Acidosis Láctica/etiología , Acidosis Láctica/genética , Femenino , Humanos , Recién Nacido , Enfermedades del Recién Nacido/diagnóstico , Enfermedades del Recién Nacido/genética , Enfermedades Mitocondriales/diagnóstico , Enfermedades Mitocondriales/genéticaRESUMEN
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.
Les soins de santé prodigués au Canada à des individus atteints de troubles mitochondriaux : une enquête menée auprès de médecins. Contexte: Dans le cas de patients atteints de troubles mitochondriaux rares, il est permis de croire qu'une meilleure compréhension des pratiques en matière de diagnostic et de traitement peut contribuer, au moyen des lignes directrices, à l'étalonnage et à l'établissement de priorités en ce qui regarde la recherche évaluative. Notre intention a été de décrire les soins prodigués au Canada par des médecins, notamment leur variabilité, dans le cas de ces patients. Méthodes: Pour ce faire, nous avons effectué une enquête transversale auprès de médecins canadiens qui posent des diagnostics de troubles mitochondriaux et qui prodiguent des soins continus aux patients qui en sont atteints. À cet effet, nous avons fait appel à la méthode d'enquête dite « en boule de neige ¼ (snowball sampling) afin d'identifier des participants possiblement admissibles. Ces derniers ont été ensuite contactés par la poste, et ce, à cinq reprises au maximum. Ils ont été invités à remplir un questionnaire et à le retourner par la poste ou en ligne. Ce questionnaire abordait les aspects suivants : leur expérience personnelle à titre de prestataire de soins ; leurs pratiques en matière de diagnostic et de traitement ; les défis se présentant à eux au moment d'avoir accès à des tests ou à des traitements ; et finalement leurs points de vue en ce qui regarde les priorités de la recherche. Résultats: Dans le cadre de cette enquête, nous avons reçu 58 réponses, ce qui représente un taux de 52 %. Une majorité de répondants (83 %) ont indiqué allouer 20 % ou moins de leur temps de pratique clinique aux soins de patients atteints de ces troubles. Nous avons également noté d'importantes variations concernant les soins et les diagnostics, et ce, même si les outils d'évaluation fréquemment considérés utiles sur le plan diagnostic (p. ex. : des IRM du cerveau/la spectroscopie par RM) étaient également recommandés dans des lignes directrices déjà publiées. Environ la moitié de nos répondants (49 %) recommanderaient volontiers un « cocktail ¼ de vitamines pour tous leurs patients ou la plupart d'entre eux. Quand il est question de vitamines spécifiques et de cofacteurs, nous avons cependant identifié une variation dans leurs réponses. Interrogés quant à la priorité numéro un en matière de recherche, une majorité de répondants a dit recommander la poursuite d'études portant sur la mise sur pied de traitements thérapeutiques efficaces. Conclusions: Bien que les points de vue de ces médecins canadiens en ce qui regarde les diagnostics et la prise en charge des troubles mitochondriaux soient en phase avec des recommandations publiées, d'importantes variations reflètent la persistance d'aspects incertains ainsi qu'un besoin de données empiriques afin de renforcer et de mettre à jour les protocoles de rééférence.
Asunto(s)
Encéfalo/diagnóstico por imagen , Enfermedades Mitocondriales/diagnóstico , Enfermedades Mitocondriales/terapia , Pautas de la Práctica en Medicina , Estudios Transversales , Encuestas de Atención de la Salud , Humanos , Imagen por Resonancia Magnética , Enfermedades Mitocondriales/diagnóstico por imagen , NeuroimagenRESUMEN
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.
Asunto(s)
Epilepsia/diagnóstico , Epilepsia/genética , Estudios de Asociación Genética , Discapacidad Intelectual/diagnóstico , Discapacidad Intelectual/genética , Mutación , Fenotipo , Canales Catiónicos TRPM/genética , Adolescente , Alelos , Niño , Preescolar , Facies , Femenino , Humanos , Masculino , Modelos Moleculares , Conformación Proteica , Índice de Severidad de la Enfermedad , Canales Catiónicos TRPM/químicaRESUMEN
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.
Asunto(s)
Epilepsia/etiología , Proteínas/genética , Proteínas/metabolismo , Animales , Modelos Animales de Enfermedad , Epilepsia/fisiopatología , Femenino , Células HEK293 , Humanos , Masculino , Fenotipo , Fosfato de Piridoxal/uso terapéutico , Piridoxina/deficiencia , Vitamina B 6/metabolismo , Deficiencia de Vitamina B 6/genética , Deficiencia de Vitamina B 6/metabolismo , Pez CebraRESUMEN
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.
Asunto(s)
Aminoacil-ARNt Sintetasas/genética , Mitocondrias/genética , Enfermedades Mitocondriales/genética , Proteínas Mitocondriales/genética , Fenilalanina-ARNt Ligasa/genética , Adolescente , Adulto , Aminoacil-ARNt Sintetasas/deficiencia , Niño , Preescolar , Femenino , Eliminación de Gen , Humanos , Masculino , Mitocondrias/enzimología , Mitocondrias/patología , Enfermedades Mitocondriales/enzimología , Enfermedades Mitocondriales/patología , Proteínas Mitocondriales/química , Proteínas Mitocondriales/deficiencia , Mutación/genética , Paraplejía/genética , Paraplejía/patología , Fenilalanina/genética , Fenilalanina/metabolismo , Fenilalanina-ARNt Ligasa/química , Fenilalanina-ARNt Ligasa/deficiencia , Isoformas de Proteínas/genética , Relación Estructura-Actividad , Adulto JovenRESUMEN
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.
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Proteínas Portadoras/genética , Mutación/genética , Proteínas del Tejido Nervioso/genética , Adolescente , Secuencia de Aminoácidos , Proteínas Portadoras/química , Niño , Preescolar , Femenino , Humanos , Lactante , Recién Nacido , Masculino , Proteínas del Tejido Nervioso/químicaRESUMEN
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.
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Síndrome de Hamartoma Múltiple/fisiopatología , Leucoencefalopatías/metabolismo , Fosfohidrolasa PTEN/metabolismo , Adolescente , Adulto , Trastorno del Espectro Autista/genética , Niño , Preescolar , Discapacidades del Desarrollo , Femenino , Síndrome de Hamartoma Múltiple/genética , Humanos , Inteligencia , Leucoencefalopatías/genética , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Fenotipo , Sustancia Blanca/patologíaRESUMEN
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.
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Errores Innatos del Metabolismo de los Carbohidratos/metabolismo , Suplementos Dietéticos , Glicina/administración & dosificación , Microcefalia/metabolismo , Fosfatidilcolinas/metabolismo , Fosfoglicerato-Deshidrogenasa/deficiencia , Trastornos Psicomotores/metabolismo , Convulsiones/metabolismo , Serina/biosíntesis , Transaminasas/deficiencia , Errores Innatos del Metabolismo de los Carbohidratos/sangre , Errores Innatos del Metabolismo de los Carbohidratos/dietoterapia , Diferenciación Celular , Niño , Preescolar , Femenino , Glicina/sangre , Humanos , Lactante , Masculino , Metabolómica/métodos , Microcefalia/sangre , Microcefalia/dietoterapia , Neuronas/metabolismo , Fosfoglicerato-Deshidrogenasa/sangre , Fosfoglicerato-Deshidrogenasa/metabolismo , Trastornos Psicomotores/sangre , Trastornos Psicomotores/dietoterapia , Convulsiones/sangre , Convulsiones/dietoterapia , Serina/administración & dosificación , Serina/sangre , Transaminasas/sangre , Transaminasas/metabolismoRESUMEN
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.
Asunto(s)
Adenosina Desaminasa/genética , Enfermedades Autoinmunes del Sistema Nervioso/genética , Enfermedades Autoinmunes del Sistema Nervioso/inmunología , Interferón Tipo I/metabolismo , Malformaciones del Sistema Nervioso/genética , Malformaciones del Sistema Nervioso/inmunología , Proteínas de Unión al ARN/genética , Adolescente , Adulto , Enfermedades Autoinmunes del Sistema Nervioso/diagnóstico por imagen , Biomarcadores/metabolismo , Niño , Preescolar , Femenino , Humanos , Lactante , Masculino , Mutación , Malformaciones del Sistema Nervioso/diagnóstico por imagen , Fenotipo , Adulto JovenRESUMEN
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.
Asunto(s)
Displasia Cleidocraneal/genética , Displasia Ectodérmica/genética , Deformidades Congénitas de las Extremidades/genética , Proteínas de la Membrana/genética , Micrognatismo/genética , Mutación , Alelos , Células Cultivadas , Displasia Cleidocraneal/diagnóstico , Displasia Ectodérmica/diagnóstico , Femenino , Fibroblastos/citología , Fibroblastos/efectos de los fármacos , Fibroblastos/metabolismo , Humanos , Recién Nacido , Inositol/metabolismo , Péptidos y Proteínas de Señalización Intracelular , Deformidades Congénitas de las Extremidades/diagnóstico , Proteínas de la Membrana/metabolismo , Micrognatismo/diagnóstico , Fenotipo , Ftalimidas/farmacología , Quinolinas/farmacología , Vacuolas/metabolismoRESUMEN
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.
Asunto(s)
Estudios de Asociación Genética/métodos , Pruebas Genéticas/métodos , Secuenciación de Nucleótidos de Alto Rendimiento , Unidades de Cuidado Intensivo Neonatal , Enfermedades Raras/diagnóstico , Enfermedades Raras/genética , Femenino , Humanos , Recién Nacido , Masculino , Mutación , Ontario , Proyectos Piloto , Estudios Prospectivos , Estudios RetrospectivosRESUMEN
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.