RESUMO
ALKBH8 is a methyltransferase that modifies tRNAs by methylating the anticodon wobble uridine residue. The syndrome of ALKBH8-related intellectual developmental disability (MRT71) has thus far been reported solely in the context of homozygous truncating variants that cluster in the last exon. This raises interesting questions about the disease mechanism, because these variants are predicted to escape nonsense mediated decay and yet they appear to be loss of function. Furthermore, the limited class of reported variants complicates the future interpretation of missense variants in ALKBH8. Here, we report a consanguineous family in which two children with MRT71-compatible phenotype are homozygous for a novel missense variant in the methyltransferase domain. We confirm the pathogenicity of this variant by demonstrating complete absence of ALKBH8-dependent modifications in patient cells. Targeted proteomics analysis of ALKBH8 indicates that the variant does not lead to loss of ALKBH8 protein expression. This report adds to the clinical delineation of MRT71, confirms loss of function of ALKBH8 as the disease mechanism and expands the repertoire of its molecular lesions.
Assuntos
Homólogo AlkB 8 da RNAt Metiltransferase/genética , Deficiências do Desenvolvimento/genética , Deficiência Intelectual/genética , Mutação de Sentido Incorreto , Homólogo AlkB 8 da RNAt Metiltransferase/química , Homólogo AlkB 8 da RNAt Metiltransferase/metabolismo , Sequência de Aminoácidos , Criança , Consanguinidade , Sequência Conservada , Deficiências do Desenvolvimento/enzimologia , Feminino , Homozigoto , Humanos , Deficiência Intelectual/enzimologia , Masculino , Microcefalia/genética , Modelos Moleculares , Linhagem , Processamento Pós-Transcricional do RNA , Convulsões/genéticaRESUMO
Mutations in genes encoding mitochondrial aminoacyl-tRNA synthetases are linked to diverse diseases. However, the precise mechanisms by which these mutations affect mitochondrial function and disease development are not fully understood. Here, we develop a Drosophila model to study the function of dFARS2, the Drosophila homologue of the mitochondrial phenylalanyl-tRNA synthetase, and further characterize human disease-associated FARS2 variants. Inactivation of dFARS2 in Drosophila leads to developmental delay and seizure. Biochemical studies reveal that dFARS2 is required for mitochondrial tRNA aminoacylation, mitochondrial protein stability, and assembly and enzyme activities of OXPHOS complexes. Interestingly, by modeling FARS2 mutations associated with human disease in Drosophila, we provide evidence that expression of two human FARS2 variants, p.G309S and p.D142Y, induces seizure behaviors and locomotion defects, respectively. Together, our results not only show the relationship between dysfunction of mitochondrial aminoacylation system and pathologies, but also illustrate the application of Drosophila model for functional analysis of human disease-causing variants.
Assuntos
Deficiências do Desenvolvimento/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Proteínas Mitocondriais/genética , Mutação , Fenilalanina-tRNA Ligase/genética , RNA de Transferência/genética , Convulsões/genética , Animais , Linhagem Celular , Deficiências do Desenvolvimento/enzimologia , Modelos Animais de Doenças , Proteínas de Drosophila/deficiência , Drosophila melanogaster/enzimologia , Técnicas de Silenciamento de Genes , Humanos , Microscopia Eletrônica de Transmissão , Mitocôndrias/genética , Mitocôndrias/metabolismo , Mitocôndrias/ultraestrutura , Proteínas Mitocondriais/deficiência , Fosforilação Oxidativa , Fenilalanina-tRNA Ligase/deficiência , RNA de Transferência/metabolismo , Convulsões/enzimologia , Aminoacilação de RNA de TransferênciaRESUMO
The positive regulatory (PR) domain containing 13 (PRDM13) putative chromatin modifier and transcriptional regulator functions downstream of the transcription factor PTF1A, which controls GABAergic fate in the spinal cord and neurogenesis in the hypothalamus. Here, we report a recessive syndrome associated with PRDM13 mutation. Patients exhibited intellectual disability, ataxia with cerebellar hypoplasia, scoliosis, and delayed puberty with congenital hypogonadotropic hypogonadism (CHH). Expression studies revealed Prdm13/PRDM13 transcripts in the developing hypothalamus and cerebellum in mouse and human. An analysis of hypothalamus and cerebellum development in mice homozygous for a Prdm13 mutant allele revealed a significant reduction in the number of Kisspeptin (Kiss1) neurons in the hypothalamus and PAX2+ progenitors emerging from the cerebellar ventricular zone. The latter was accompanied by ectopic expression of the glutamatergic lineage marker TLX3. Prdm13-deficient mice displayed cerebellar hypoplasia and normal gonadal structure, but delayed pubertal onset. Together, these findings identify PRDM13 as a critical regulator of GABAergic cell fate in the cerebellum and of hypothalamic kisspeptin neuron development, providing a mechanistic explanation for the cooccurrence of CHH and cerebellar hypoplasia in this syndrome. To our knowledge, this is the first evidence linking disrupted PRDM13-mediated regulation of Kiss1 neurons to CHH in humans.
Assuntos
Cerebelo/anormalidades , Histona-Lisina N-Metiltransferase , Hipogonadismo , Hipotálamo/enzimologia , Mutação , Malformações do Sistema Nervoso , Fatores de Transcrição , Animais , Cerebelo/enzimologia , Deficiências do Desenvolvimento/enzimologia , Deficiências do Desenvolvimento/genética , Modelos Animais de Doenças , Histona-Lisina N-Metiltransferase/genética , Histona-Lisina N-Metiltransferase/metabolismo , Humanos , Hipogonadismo/enzimologia , Hipogonadismo/genética , Camundongos , Camundongos Mutantes , Malformações do Sistema Nervoso/enzimologia , Malformações do Sistema Nervoso/genética , Neurônios/enzimologia , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
BACKGROUND: Haploinsufficiency of the human nuclear receptor binding suppressor of variegation 3-9, enhancer of zeste, and trithorax (SET) domain 1 (NSD1) gene causes a developmental disorder called Sotos syndrome 1 (SOTOS1), which is associated with overgrowth and macrocephaly. NSD family proteins encoding histone H3 lysine 36 (H3K36) methyltransferases are conserved in many species, and Drosophila has a single NSD homolog gene, NSD. OBJECTIVE: To gain insight into the biological functions of NSD1 deficiency in the developmental anomalies seen in SOTOS1 patients using an NSD-deleted Drosophila mutant. METHODS: We deleted Drosophila NSD using CRISPR/Cas9-mediated targeted gene knock-out, and analyzed pleiotropic phenotypes of the homozygous mutant of NSD (NSD-/-) at various developmental stages to understand the roles of NSD in Drosophila. RESULTS: The site-specific NSD deletion was confirmed in the mutant. The H3K36 di-methylation levels were dramatically decreased in the NSD-/- fly. Compared with the control, the NSD-/- fly displayed an increase in the body size of larvae, similar to the childhood overgrowth phenotype of SOTOS1 patients. Although the NSD mutant flies survived to adulthood, their fecundity was dramatically decreased. Furthermore, the NSD-/- fly showed neurological dysfunctions, such as lower memory performance and motor defects, and a diminished extracellular signal-regulated kinase (ERK) activity. CONCLUSIONS: The NSD-deleted Drosophila phenotype resembles many of the phenotypes of SOTOS1 patients, such as learning disability, deregulated ERK signaling, and overgrowth; thus, this mutant fly is a relevant model organism to study various SOTOS1 phenotypes.
Assuntos
Modelos Animais de Doenças , Drosophila , Histona-Lisina N-Metiltransferase/genética , Síndrome de Sotos/genética , Animais , Deficiências do Desenvolvimento/enzimologia , Deficiências do Desenvolvimento/genética , Drosophila/genética , Feminino , Deleção de Genes , Humanos , Masculino , Síndrome de Sotos/enzimologiaRESUMO
Glycosylphosphatidylinositol (GPI) is a glycolipid that anchors >150 proteins to the cell surface. Pathogenic variants in several genes that participate in GPI biosynthesis cause inherited GPI deficiency disorders. Here, we reported that homozygous null alleles of PIGG, a gene involved in GPI modification, are responsible for the rare Emm-negative blood phenotype. Using a panel of K562 cells defective in both the GPI-transamidase and GPI remodeling pathways, we show that the Emm antigen, whose molecular basis has remained unknown for decades, is carried only by free GPI and that its epitope is composed of the second and third ethanolamine of the GPI backbone. Importantly, we show that the decrease in Emm expression in several inherited GPI deficiency patients is indicative of GPI defects. Overall, our findings establish Emm as a novel blood group system, and they have important implications for understanding the biological function of human free GPI.
Assuntos
Antígenos de Grupos Sanguíneos , Deficiências do Desenvolvimento , Glicosilfosfatidilinositóis/deficiência , Glicosilfosfatidilinositóis/metabolismo , Fosfotransferases (Aceptor do Grupo Álcool) , Convulsões , Antígenos de Grupos Sanguíneos/genética , Antígenos de Grupos Sanguíneos/metabolismo , Deficiências do Desenvolvimento/enzimologia , Deficiências do Desenvolvimento/genética , Glicosilfosfatidilinositóis/genética , Humanos , Células K562 , Fosfotransferases (Aceptor do Grupo Álcool)/genética , Fosfotransferases (Aceptor do Grupo Álcool)/metabolismo , Convulsões/enzimologia , Convulsões/genéticaRESUMO
Creatine kinase (CK) is considered the main phosphotransfer system in the heart, important for overcoming diffusion restrictions and regulating mitochondrial respiration. It is substrate limited in creatine-deficient mice lacking l-arginine:glycine amidinotransferase (AGAT) or guanidinoacetate N-methyltranferase (GAMT). Our aim was to determine the expression, activity, and mitochondrial coupling of hexokinase (HK) and adenylate kinase (AK), as these represent alternative energy transfer systems. In permeabilized cardiomyocytes, we assessed how much endogenous ADP generated by HK, AK, or CK stimulated mitochondrial respiration and how much was channeled to mitochondria. In whole heart homogenates, and cytosolic and mitochondrial fractions, we measured the activities of AK, CK, and HK. Lastly, we assessed the expression of the major HK, AK, and CK isoforms. Overall, respiration stimulated by HK, AK, and CK was â¼25, 90, and 80%, respectively, of the maximal respiration rate, and â¼20, 0, and 25%, respectively, was channeled to the mitochondria. The activity, distribution, and expression of HK, AK, and CK did not change in GAMT knockout (KO) mice. In AGAT KO mice, we found no changes in AK, but we found a higher HK activity in the mitochondrial fraction, greater expression of HK I, but a lower stimulation of respiration by HK. Our findings suggest that mouse hearts depend less on phosphotransfer systems to facilitate ADP flux across the mitochondrial membrane. In AGAT KO mice, which are a model of pure creatine deficiency, the changes in HK may reflect changes in metabolism as well as influence mitochondrial regulation and reactive oxygen species production.NEW & NOTEWORTHY In creatine-deficient AGAT-/- and GAMT-/- mice, the myocardial creatine kinase system is substrate limited. It is unknown whether subcellular localization and mitochondrial ADP channeling by hexokinase and adenylate kinase may compensate as alternative phosphotransfer systems. Our results show no changes in adenylate kinase, which is the main alternative to creatine kinase in heart. However, we found increased expression and activity of hexokinase I in AGAT-/- cardiomyocytes. This could affect mitochondrial regulation and reactive oxygen species production.
Assuntos
Amidinotransferases/deficiência , Erros Inatos do Metabolismo dos Aminoácidos/enzimologia , Creatina/deficiência , Metabolismo Energético , Guanidinoacetato N-Metiltransferase/deficiência , Hexoquinase/metabolismo , Deficiência Intelectual/enzimologia , Transtornos do Desenvolvimento da Linguagem/enzimologia , Mitocôndrias Cardíacas/enzimologia , Transtornos dos Movimentos/congênito , Miócitos Cardíacos/enzimologia , Distúrbios da Fala/enzimologia , Difosfato de Adenosina/metabolismo , Adenilato Quinase/metabolismo , Amidinotransferases/genética , Erros Inatos do Metabolismo dos Aminoácidos/genética , Animais , Respiração Celular , Creatina Quinase/metabolismo , Deficiências do Desenvolvimento/enzimologia , Deficiências do Desenvolvimento/genética , Modelos Animais de Doenças , Feminino , Guanidinoacetato N-Metiltransferase/genética , Deficiência Intelectual/genética , Transtornos do Desenvolvimento da Linguagem/genética , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Transtornos dos Movimentos/enzimologia , Transtornos dos Movimentos/genética , Distúrbios da Fala/genéticaRESUMO
Hexokinase (EC 2.7.1.1, Adenosine Tri Phosphate (ATP): D-hexose-6-phosphotransferase) is a crucial regulatory enzyme of the glycolytic pathway (Embden-Meyerhof pathway). Hexokinase deficiency is associated with chronic non-spherocytic haemolytic anaemia (HA) with some exceptional cases showing psychomotor/mental retardation and fetus death. The proband is a four-and-half-year-old female child born of a four-degree consanguineous marriage hailing from South India with autosomal recessive congenital HA associated with developmental delay. She was well till 3 months of her age post an episode of diarrhoea when she was noted to be severely anaemic and requiring regular transfusions. The common causes of HA, haemoglobinopathies, red cell membranopathies and common red cell enzymopathies (G6PD, GPI, PK and P5N) were ruled out. Targeted analysis of whole exome sequencing (WES) using an insilico gene panel for hereditary anaemia was performed to identify pathogenic variants in the patient. Next-generation sequencing revealed a novel homozygous variant in hexokinase gene c.2714C>A (p. Thr905Lys) in exon-18. The pathogenic nature of the variant p. Thr905Lys in the HK1 gene was confirmed collectively by biochemical and molecular studies. Insilico analysis (PolyPhen-2, Provean, Mutation Taster) predicted the variant to be severe disease causing. Multiple sequence alignment demonstrated the conservation of p. Thr905 across the species. The impact of the mutation on the protein structure was studied by PyMOL and Swiss Protein databank viewer.
Assuntos
Anemia Hemolítica/genética , Deficiências do Desenvolvimento/genética , Hexoquinase/deficiência , Mutação de Sentido Incorreto , Adulto , Fatores Etários , Anemia Hemolítica/diagnóstico , Anemia Hemolítica/enzimologia , Desenvolvimento Infantil , Pré-Escolar , Análise Mutacional de DNA , Deficiências do Desenvolvimento/diagnóstico , Deficiências do Desenvolvimento/enzimologia , Feminino , Predisposição Genética para Doença , Hereditariedade , Hexoquinase/genética , Hexoquinase/metabolismo , Sequenciamento de Nucleotídeos em Larga Escala , Homozigoto , Humanos , Índia , Masculino , Linhagem , Fenótipo , Índice de Gravidade de Doença , Sequenciamento do Exoma , Adulto JovemRESUMO
Succinic semialdehyde dehydrogenase deficiency (SSADHD) is a rare, monogenic disorder affecting the degradation of the main inhibitory neurotransmitter γ-amino butyric acid (GABA). Pathogenic variants in the ALDH5A1 gene that cause an enzymatic dysfunction of succinic semialdehyde dehydrogenase (SSADH) lead to an accumulation of potentially toxic metabolites, including γ-hydroxybutyrate (GHB). Here, we present a patient with a severe phenotype of SSADHD caused by a novel genetic variant c.728T > C that leads to an exchange of leucine to proline at residue 243, located within the highly conserved nicotinamide adenine dinucleotide (NAD)+ binding domain of SSADH. Proline harbors a pyrrolidine within its side chain known for its conformational rigidity and disruption of protein secondary structures. We investigate the effect of this novel variant in vivo, in vitro, and in silico. We furthermore examine the mutational spectrum of all previously described disease-causing variants and computationally assess all biologically possible missense variants of ALDH5A1 to identify mutational hotspots.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos , Simulação por Computador , Deficiências do Desenvolvimento , Mutação de Sentido Incorreto , Succinato-Semialdeído Desidrogenase/deficiência , Erros Inatos do Metabolismo dos Aminoácidos/enzimologia , Erros Inatos do Metabolismo dos Aminoácidos/genética , Substituição de Aminoácidos , Deficiências do Desenvolvimento/enzimologia , Deficiências do Desenvolvimento/genética , Células HEK293 , Humanos , Domínios Proteicos , Succinato-Semialdeído Desidrogenase/genética , Succinato-Semialdeído Desidrogenase/metabolismoRESUMO
Dual-specificity tyrosine phosphorylation-regulated kinase 1 A (DYRK1A) is essential for human development, and DYRK1A haploinsufficiency is associated with a recognizable developmental syndrome and variable clinical features. Here, we present a patient with DYRK1A haploinsufficiency syndrome, including facial dysmorphism, delayed motor development, cardiovascular system defects, and brain atrophy. Exome sequencing identified a novel de novo heterozygous mutation of the human DYRK1A gene (c.1185dup), which generated a translational termination codon and resulted in a C-terminally truncated protein (DYRK1A-E396ter). To study the molecular effect of this truncation, we generated mammalian cell and Drosophila models that recapitulated the DYRK1A protein truncation. Analysis of the structure and deformation energy of the mutant protein predicted a reduction in protein stability. Experimentally, the mutant protein was efficiently degraded by the ubiquitin-dependent proteasome pathway and was barely detectable in mammalian cells. More importantly, the mutant kinase was intrinsically inactive and had little negative impact on the wild-type protein. Similarly, the mutant protein had a minimal effect on Drosophila phenotypes, confirming its loss-of-function in vivo. Together, our results suggest that the novel heterozygous mutation of DYRK1A resulted in loss-of-function of the kinase activity of DYRK1A and may contribute to the developmental delay observed in the patient.
Assuntos
Deficiências do Desenvolvimento/enzimologia , Deficiências do Desenvolvimento/genética , Heterozigoto , Mutação , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Tirosina Quinases/genética , Proteínas Tirosina Quinases/metabolismo , Animais , Drosophila melanogaster , Feminino , Células HEK293 , Humanos , Lactente , Masculino , Simulação de Dinâmica Molecular , Linhagem , Conformação Proteica em Folha beta , Domínios Proteicos , Proteínas Serina-Treonina Quinases/química , Proteínas Tirosina Quinases/química , Quinases DyrkRESUMO
Inborn errors of metabolism can cause epileptic encephalopathies. Biallelic loss-of-function variants in the ITPA gene, encoding inosine triphosphate pyrophosphatase (ITPase), have been reported in epileptic encephalopathies with lack of myelination of the posterior limb of the internal capsule, brainstem tracts, and tracts to the primary visual and motor cortices (MIM:616647). ITPase plays an important role in purine metabolism. In this study, we identified two novel homozygous ITPA variants, c.264-1 G > A and c.489-1 G > A, in two unrelated consanguineous families. The probands had epilepsy, microcephaly with characteristic magnetic resonance imaging findings (T2 hyperintensity signals in the pyramidal tracts of the internal capsule, delayed myelination, and thin corpus callosum), hypotonia, and developmental delay; both died in early infancy. Our report expands the knowledge of clinical consequences of biallelic ITPA variants.
Assuntos
Encefalopatias/genética , Deficiências do Desenvolvimento/genética , Epilepsia/genética , Predisposição Genética para Doença , Insuficiência de Múltiplos Órgãos/genética , Hipotonia Muscular/genética , Pirofosfatases/genética , Encefalopatias/complicações , Encefalopatias/enzimologia , Encefalopatias/mortalidade , Corpo Caloso/diagnóstico por imagem , Corpo Caloso/patologia , Deficiências do Desenvolvimento/complicações , Deficiências do Desenvolvimento/enzimologia , Deficiências do Desenvolvimento/mortalidade , Epilepsia/complicações , Epilepsia/enzimologia , Epilepsia/mortalidade , Feminino , Genótipo , Homozigoto , Humanos , Lactente , Imageamento por Ressonância Magnética , Masculino , Insuficiência de Múltiplos Órgãos/complicações , Insuficiência de Múltiplos Órgãos/enzimologia , Insuficiência de Múltiplos Órgãos/mortalidade , Hipotonia Muscular/complicações , Hipotonia Muscular/enzimologia , Hipotonia Muscular/mortalidade , Mutação , Linhagem , Tratos Piramidais/diagnóstico por imagem , Tratos Piramidais/patologia , Sequenciamento do ExomaRESUMO
PURPOSE: We aimed to identify prognostic factors for survival and long-term intellectual and developmental outcome in neonatal patients with early-onset urea cycle disorders (UCD) experiencing hyperammonaemic coma. METHODS: We retrospectively analysed ammonia (NH3) and glutamine levels, electroencephalogram and brain images obtained during neonatal coma of UCD patients born between 1995 and 2011 and managed at a single centre and correlated them to survival and intellectual and developmental outcome. RESULTS: We included 38 neonates suffering from deficiencies of argininosuccinate synthetase (ASSD, N = 12), ornithine transcarbamylase (OTCD, N = 10), carbamoylphosphate synthetase 1 (CPSD, N = 7), argininosuccinate lyase (ASLD, N = 7), N-acetylglutamate synthase (NAGS, N = 1) or arginase (ARGD, N = 1). Symptoms occurred earlier in mitochondrial than in cytosolic UCD. Sixty-eight percent of patients survived, with a mean (standard deviation-SD) follow-up of 10.4 (5.3) years. Mortality was mostly observed in OTCD (N = 7/10) and CPSD (N = 4/7) patients. Plasma NH3 level during the neonatal period, expressed as area under the curve, but not glutamine level was associated with mortality (p = .044 and p = .610). 62.1% of the patients had normal intellectual and developmental outcome. Intellectual and developmental outcome tended to correlate with UCD subtype (p = .052). No difference in plasma NH3 or glutamine level during the neonatal period among developmental outcomes was identified. EEG severity was linked to UCD subtypes (p = .004), ammonia levels (p = .037), duration of coma (p = .043), and mortality during the neonatal period (p = .020). Status epilepticus was recorded in 6 patients, 3 of whom died neonatally, 1 developed a severe intellectual disability while the 2 last patients had a normal development. CONCLUSION: UCD subtypes differed by survival rate, intellectual and developmental outcome and EEG features in the neonatal period. Hyperammonaemia expressed as area under the curve was associated with survival but not with intellectual and developmental outcome whereas glutamine was not associated with one of these outcomes. Prognostic value of video-EEG monitoring and the association between status epilepticus and mortality should be assessed in neonatal hyperammonaemic coma in further studies.
Assuntos
Argininossuccinato Sintase/metabolismo , Carbamoil-Fosfato Sintase (Amônia)/metabolismo , Deficiências do Desenvolvimento/epidemiologia , Mortalidade Infantil/tendências , Deficiência Intelectual/epidemiologia , Ornitina Carbamoiltransferase/metabolismo , Distúrbios Congênitos do Ciclo da Ureia/mortalidade , Idade de Início , Amônia/sangue , Deficiências do Desenvolvimento/enzimologia , Deficiências do Desenvolvimento/patologia , Feminino , França/epidemiologia , Humanos , Lactente , Recém-Nascido , Deficiência Intelectual/enzimologia , Deficiência Intelectual/patologia , Masculino , Estudos Retrospectivos , Distúrbios Congênitos do Ciclo da Ureia/enzimologia , Distúrbios Congênitos do Ciclo da Ureia/patologiaRESUMO
Succinic semialdehyde dehydrogenase deficiency (SSADH-D) is a genetic disorder that results from the aberrant metabolism of the neurotransmitter γ-amino butyric acid (GABA). The disease is caused by impaired activity of the mitochondrial enzyme succinic semialdehyde dehydrogenase. SSADH-D manifests as varying degrees of mental retardation, autism, ataxia, and epileptic seizures, but the clinical picture is highly heterogeneous. So far, there is no approved curative therapy for this disease. In this review, we briefly summarize the molecular genetics of SSADH-D, the past and ongoing clinical trials, and the emerging features of the molecular pathogenesis, including redox imbalance and mitochondrial dysfunction. The main aim of this review is to discuss the potential of further therapy approaches that have so far not been tested in SSADH-D, such as pharmacological chaperones, read-through drugs, and gene therapy. Special attention will also be paid to elucidating the role of patient advocacy organizations in facilitating research and in the communication between researchers and patients.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos/tratamento farmacológico , Erros Inatos do Metabolismo dos Aminoácidos/genética , Deficiências do Desenvolvimento/tratamento farmacológico , Deficiências do Desenvolvimento/genética , Terapia de Reposição de Enzimas/métodos , Terapia Genética/métodos , Terapia de Alvo Molecular/métodos , Succinato-Semialdeído Desidrogenase/deficiência , Adulto , Erros Inatos do Metabolismo dos Aminoácidos/enzimologia , Erros Inatos do Metabolismo dos Aminoácidos/fisiopatologia , Animais , Criança , Ensaios Clínicos como Assunto , Deficiências do Desenvolvimento/enzimologia , Deficiências do Desenvolvimento/fisiopatologia , Modelos Animais de Doenças , Humanos , Camundongos , Mutação , Succinato-Semialdeído Desidrogenase/química , Succinato-Semialdeído Desidrogenase/genética , Ácido gama-Aminobutírico/metabolismoRESUMO
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.
Assuntos
Aminoacil-tRNA Sintetases/genética , Doença de Charcot-Marie-Tooth/etiologia , Deficiências do Desenvolvimento/etiologia , Doenças do Cabelo/etiologia , Microcefalia/etiologia , Mutação , Doenças da Unha/etiologia , Adulto , Sequência de Aminoácidos , Doença de Charcot-Marie-Tooth/enzimologia , Doença de Charcot-Marie-Tooth/patologia , Deficiências do Desenvolvimento/enzimologia , Deficiências do Desenvolvimento/patologia , Feminino , Genes Recessivos , Predisposição Genética para Doença , Doenças do Cabelo/enzimologia , Doenças do Cabelo/patologia , Humanos , Masculino , Microcefalia/enzimologia , Microcefalia/patologia , Doenças da Unha/enzimologia , Doenças da Unha/patologia , Linhagem , Fenótipo , Prognóstico , Homologia de Sequência , Adulto JovemRESUMO
No disponible
Assuntos
Humanos , Masculino , Lactente , Glicerol Quinase/deficiência , Deficiências do Desenvolvimento/enzimologia , Transtorno Autístico/enzimologia , Transtorno Autístico/genética , Glicerol Quinase/metabolismo , Espectrometria de Fluorescência/métodos , Diabetes Gestacional , Diagnóstico DiferencialRESUMO
Hypusine is formed post-translationally from lysine and is found in a single cellular protein, eukaryotic translation initiation factor-5A (eIF5A), and its homolog eIF5A2. Biosynthesis of hypusine is a two-step reaction involving the enzymes deoxyhypusine synthase (DHPS) and deoxyhypusine hydroxylase (DOHH). eIF5A is highly conserved throughout eukaryotic evolution and plays a role in mRNA translation, cellular proliferation, cellular differentiation, and inflammation. DHPS is also highly conserved and is essential for life, as Dhps-null mice are embryonic lethal. Using exome sequencing, we identified rare biallelic, recurrent, predicted likely pathogenic variants in DHPS segregating with disease in five affected individuals from four unrelated families. These individuals have similar neurodevelopmental features that include global developmental delay and seizures. Two of four affected females have short stature. All five affected individuals share a recurrent missense variant (c.518A>G [p.Asn173Ser]) in trans with a likely gene disrupting variant (c.1014+1G>A, c.912_917delTTACAT [p.Tyr305_Ile306del], or c.1A>G [p.Met1?]). cDNA studies demonstrated that the c.1014+1G>A variant causes aberrant splicing. Recombinant DHPS enzyme harboring either the p.Asn173Ser or p.Tyr305_Ile306del variant showed reduced (20%) or absent in vitro activity, respectively. We co-transfected constructs overexpressing HA-tagged DHPS (wild-type or mutant) and GFP-tagged eIF5A into HEK293T cells to determine the effect of these variants on hypusine biosynthesis and observed that the p.Tyr305_Ile306del and p.Asn173Ser variants resulted in reduced hypusination of eIF5A compared to wild-type DHPS enzyme. Our data suggest that rare biallelic variants in DHPS result in reduced enzyme activity that limits the hypusination of eIF5A and are associated with a neurodevelopmental disorder.
Assuntos
Genes Recessivos/genética , Lisina/análogos & derivados , Mutação , Transtornos do Neurodesenvolvimento/enzimologia , Transtornos do Neurodesenvolvimento/genética , Oxirredutases atuantes sobre Doadores de Grupo CH-NH/genética , Alelos , Sequência de Aminoácidos , Criança , Pré-Escolar , Deficiências do Desenvolvimento/enzimologia , Deficiências do Desenvolvimento/genética , Feminino , Haplótipos , Humanos , Lisina/biossíntese , Masculino , Erros Inatos do Metabolismo/enzimologia , Erros Inatos do Metabolismo/genética , Oxirredutases atuantes sobre Doadores de Grupo CH-NH/química , Oxirredutases atuantes sobre Doadores de Grupo CH-NH/metabolismo , Linhagem , Fatores de Iniciação de Peptídeos/química , Fatores de Iniciação de Peptídeos/metabolismo , Proteínas de Ligação a RNA/química , Proteínas de Ligação a RNA/metabolismo , Convulsões/enzimologia , Convulsões/genética , Adulto Jovem , Fator de Iniciação de Tradução Eucariótico 5ARESUMO
Adenosine kinase (ADK) deficiency (OMIM [online mendelian inheritance in man]: 614300) is an autosomal recessive disorder of adenosine and methionine metabolism, with a unique clinical phenotype, mainly involving the central nervous system and dysmorphic features. Patients usually present early in life with sepsis-like symptoms, respiratory difficulties, and neonatal jaundice. Subsequently, patients demonstrate hypotonia and global developmental delay. Biochemically, methionine is elevated with normal homocysteine levels and the diagnosis is confirmed through molecular analysis of the ADK gene. There is no curative treatment; however, a methionine-restricted diet has been tried with variable outcomes. Herein, we report a 4-year-old Saudi female with global developmental delay, hypotonia, and dysmorphic features. Interestingly, she has a tall stature, developmental dysplasia of the hip, optic nerve gliosis, and tigroid fundus. We found a mutation not reported previously and we compared the current case with previously reported cases. We alert clinicians to consider ADK deficiency in any neonate presenting with global developmental delay, hypotonia, dysmorphic features, and high methionine levels.
Assuntos
Adenosina Quinase/deficiência , Deficiências do Desenvolvimento/diagnóstico por imagem , Deficiências do Desenvolvimento/enzimologia , Hipotonia Muscular/diagnóstico por imagem , Hipotonia Muscular/enzimologia , Pré-Escolar , Feminino , HumanosRESUMO
Succinic semialdehyde dehydrogenase deficiency (SSADHD) is a rare autosomal recessive metabolic disorder of GABA catabolism. SSADH is a mitochondrial homotetrameric enzyme encoded by ALDH5A1 gene. We report the molecular characterization of ALDH5A1 gene in an Italian SSADHD patient, showing heterozygosity for four missense mutations: c.526G>A (p.G176R), c.538C>T (p.H180Y), c.709G>T (p.A237S) and c.1267A>T (p.T423S), the latter never described so far. The patient inherited c.526A in cis with c.538T from the mother and c.709T in cis with c.1267T from the father. To explore the effects of the two allelic arrangements on SSADH activity and protein level, wild type, single or double mutated cDNA constructs were expressed in a cell system. The p.G176R change, alone or in combination with p.H180Y, causes the abolishment of enzyme activity. Western blot analysis showed a strongly reduced amount of the p.176R-p.180Y double mutant protein, suggesting increased degradation. Indeed, in silico analyses confirmed high instability of this mutant homotetramer. Enzyme activity relative to the other p.423S-p.237S double mutant is around 30% of wt. Further in silico analyses on all the possible combinations of mutant monomers suggest the lowest stability for the tetramer constituted by p.176R-p.180Y monomers and the highest stability for that constituted by p.237S-p.423S monomers. The present study shows that when a common SNP, associated with a slight reduction of SSADH activity, is inherited in cis with a mutation showing no consequences on the enzyme function, the activity is strongly affected. In conclusion, the peculiar arrangement of four missense mutations occurring in this patient is responsible for the SSADHD phenotype.
Assuntos
Erros Inatos do Metabolismo dos Aminoácidos/patologia , Deficiências do Desenvolvimento/patologia , Mutação de Sentido Incorreto , Polimorfismo de Nucleotídeo Único , Succinato-Semialdeído Desidrogenase/deficiência , Erros Inatos do Metabolismo dos Aminoácidos/enzimologia , Erros Inatos do Metabolismo dos Aminoácidos/genética , Pré-Escolar , Deficiências do Desenvolvimento/enzimologia , Deficiências do Desenvolvimento/genética , Estabilidade Enzimática , Feminino , Heterozigoto , Humanos , Masculino , Linhagem , Conformação Proteica , Succinato-Semialdeído Desidrogenase/química , Succinato-Semialdeído Desidrogenase/genética , Succinato-Semialdeído Desidrogenase/metabolismoAssuntos
Carbono-Nitrogênio Ligases com Glutamina como Doadora de N-Amida/genética , Deficiências do Desenvolvimento/genética , Microcefalia/genética , Espasticidade Muscular/genética , Mutação , Carbono-Nitrogênio Ligases com Glutamina como Doadora de N-Amida/deficiência , Deficiências do Desenvolvimento/diagnóstico por imagem , Deficiências do Desenvolvimento/enzimologia , Deficiências do Desenvolvimento/patologia , Éxons , Expressão Gênica , Homozigoto , Humanos , Imageamento por Ressonância Magnética , Microcefalia/diagnóstico por imagem , Microcefalia/enzimologia , Microcefalia/patologia , Espasticidade Muscular/diagnóstico por imagem , Espasticidade Muscular/enzimologia , Espasticidade Muscular/patologia , Sequenciamento do ExomaAssuntos
Erros Inatos do Metabolismo dos Aminoácidos/fisiopatologia , Deficiências do Desenvolvimento/enzimologia , Succinato-Semialdeído Desidrogenase/deficiência , Erros Inatos do Metabolismo dos Aminoácidos/diagnóstico por imagem , Pré-Escolar , Deficiências do Desenvolvimento/diagnóstico por imagem , Deficiências do Desenvolvimento/fisiopatologia , Globo Pálido/diagnóstico por imagem , Humanos , Lamotrigina/uso terapêutico , Imageamento por Ressonância Magnética , Masculino , Transtornos Motores/tratamento farmacológico , Transtornos Motores/enzimologia , Transtornos Motores/fisiopatologia , Hipotonia Muscular/enzimologia , Hipotonia Muscular/fisiopatologia , Risperidona/uso terapêuticoRESUMO
Histone lysine methyltransferases (KMTs) and demethylases (KDMs) underpin gene regulation. Here we demonstrate that variants causing haploinsufficiency of KMTs and KDMs are frequently encountered in individuals with developmental disorders. Using a combination of human variation databases and existing animal models, we determine 22 KMTs and KDMs as additional candidates for dominantly inherited developmental disorders. We show that KMTs and KDMs that are associated with, or are candidates for, dominant developmental disorders tend to have a higher level of transcription, longer canonical transcripts, more interactors, and a higher number and more types of post-translational modifications than other KMT and KDMs. We provide evidence to firmly associate KMT2C, ASH1L, and KMT5B haploinsufficiency with dominant developmental disorders. Whereas KMT2C or ASH1L haploinsufficiency results in a predominantly neurodevelopmental phenotype with occasional physical anomalies, KMT5B mutations cause an overgrowth syndrome with intellectual disability. We further expand the phenotypic spectrum of KMT2B-related disorders and show that some individuals can have severe developmental delay without dystonia at least until mid-childhood. Additionally, we describe a recessive histone lysine-methylation defect caused by homozygous or compound heterozygous KDM5B variants and resulting in a recognizable syndrome with developmental delay, facial dysmorphism, and camptodactyly. Collectively, these results emphasize the significance of histone lysine methylation in normal human development and the importance of this process in human developmental disorders. Our results demonstrate that systematic clinically oriented pathway-based analysis of genomic data can accelerate the discovery of rare genetic disorders.