RESUMO
The ubiquitin system impacts most cellular processes and is altered in numerous neurodegenerative diseases. However, little is known about its role in neurodegenerative diseases due to disturbances of glycogen metabolism such as Lafora disease (LD). In LD, insufficiently branched and long-chained glycogen forms and precipitates into insoluble polyglucosan bodies (Lafora bodies), which drive neuroinflammation, neurodegeneration and epilepsy. LD is caused by mutations in the gene encoding the glycogen phosphatase laforin or the gene coding for the laforin interacting partner ubiquitin E3 ligase malin. The role of the malin-laforin complex in regulating glycogen structure remains with full of gaps. In this review we bring together the disparate body of data on these two proteins and propose a mechanistic hypothesis of the disease in which malin-laforin's role to monitor and prevent over-elongation of glycogen branch chains, which drive glycogen molecules to precipitate and accumulate into Lafora bodies. We also review proposed connections between Lafora bodies and the ensuing neuroinflammation, neurodegeneration and intractable epilepsy. Finally, we review the exciting activities in developing therapies for Lafora disease based on replacing the missing genes, slowing the enzyme - glycogen synthase - that over-elongates glycogen branches, and introducing enzymes that can digest Lafora bodies. Much more work is needed to fill the gaps in glycogen metabolism in which laforin and malin operate. However, knowledge appears already adequate to advance disease course altering therapies for this catastrophic fatal disease.
Assuntos
Doença de Lafora , Glicogênio/metabolismo , Humanos , Doença de Lafora/genética , Doença de Lafora/terapia , Proteínas Tirosina Fosfatases não Receptoras/genética , Proteínas Tirosina Fosfatases não Receptoras/metabolismo , Ubiquitina-Proteína LigasesRESUMO
Lafora disease is a fatal genetic disorder characterised by neurotoxic deposits of malformed insoluble glycogen. In humans it is caused by mutation in the EPM2A or NHLRC1 genes. There is a known mutation in miniature wirehaired dachshunds which has not been documented in other dog breeds, including beagles, in which the disease is relatively commonly reported. This case report describes the causative defect in two affected beagles, namely the same massive expansion as in miniature wirehaired dachshunds of a 12-nucleotide repeat sequence that is unique to the canine NHLRC1 gene. This is the first mutation described in beagles with Lafora disease, and so far the only Lafora disease genetic variant in dogs.
Assuntos
Doenças do Cão/genética , Doença de Lafora/veterinária , Animais , Proteínas de Transporte/genética , Cães , Feminino , Regulação da Expressão Gênica , Doença de Lafora/genética , Masculino , Mutação , LinhagemRESUMO
X-linked Myopathy with Excessive Autophagy (XMEA) affects proximal muscles of the lower extremities and follows a progressive course reminiscent of muscular dystrophy. It is caused by mutations in VMA21 whose protein product assembles lysosomes' proton pumps. All XMEA mutations to date have been single-nucleotide substitutions that reduce VMA21 expression, which leads to modest lysosomal pH increase, the first step in the disease's pathogenesis. We now report a new class of XMEA mutations. We identified two VMA21 non-coding microdeletions, one intronic (c.54-16_54-8del), the other in the 3'UTR (c.*13_*104del). Both resulted in a relatively more severe (early ambulation loss), diffuse (extra-ocular and upper extremity involvement), and early (neonatal) onset disease compared to previously reported patients. Our cases highlight the importance of including non-coding regions of VMA21 in genetic testing panels of dystrophies and myopathies. Specific diagnosis of XMEA will be particularly important as therapies aimed at correcting the modest rise in lysosomal pH at the root of this disease are developed.
Assuntos
Doenças Genéticas Ligadas ao Cromossomo X/genética , Doenças Musculares/genética , Deleção de Sequência , ATPases Vacuolares Próton-Translocadoras/genética , Adolescente , Autofagia/genética , Encéfalo/patologia , Encéfalo/fisiopatologia , Doenças Genéticas Ligadas ao Cromossomo X/patologia , Doenças Genéticas Ligadas ao Cromossomo X/fisiopatologia , Humanos , Imageamento por Ressonância Magnética , Masculino , Músculo Esquelético/patologia , Doenças Musculares/patologia , Doenças Musculares/fisiopatologia , RNA Mensageiro/metabolismo , ATPases Vacuolares Próton-Translocadoras/metabolismo , Adulto JovemRESUMO
AIMS/HYPOTHESIS: Endoplasmic reticulum (ER) stress has been implicated in glucose-induced beta cell dysfunction. However, its causal role has not been established in vivo. Our objective was to determine the causal role of ER stress and its link to oxidative stress in glucose-induced beta cell dysfunction in vivo. METHODS: Healthy Wistar rats were infused i.v. with glucose for 48 h to achieve 20 mmol/l hyperglycaemia with or without the co-infusion of the superoxide dismutase mimetic tempol (TPO), or the chemical chaperones 4-phenylbutyrate (PBA) or tauroursodeoxycholic acid (TUDCA). This was followed by assessment of beta cell function and measurement of ER stress markers and superoxide in islets. RESULTS: Glucose infusion for 48 h increased mitochondrial superoxide and ER stress markers and impaired beta cell function. Co-infusion of TPO, which we previously found to reduce mitochondrial superoxide and prevent glucose-induced beta cell dysfunction, reduced ER stress markers. Similar to findings with TPO, co-infusion of PBA, which decreases mitochondrial superoxide, prevented glucose-induced beta cell dysfunction in isolated islets. TUDCA was also effective. Also similar to findings with TPO, PBA prevented beta cell dysfunction during hyperglycaemic clamps in vivo and after hyperglycaemia (15 mmol/l) for 96 h. CONCLUSIONS/INTERPRETATION: Here, we causally implicate ER stress in hyperglycaemia-induced beta cell dysfunction in vivo. We show that: (1) there is a positive feedback cycle between oxidative stress and ER stress in glucose-induced beta cell dysfunction, which involves mitochondrial superoxide; and (2) this cycle can be interrupted by superoxide dismutase mimetics as well as chemical chaperones, which are of potential interest to preserve beta cell function in type 2 diabetes.
Assuntos
Estresse do Retículo Endoplasmático/efeitos dos fármacos , Glucose/efeitos adversos , Células Secretoras de Insulina/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Animais , Antioxidantes/farmacologia , Óxidos N-Cíclicos/farmacologia , Feminino , Hiperglicemia/induzido quimicamente , Hiperglicemia/metabolismo , Células Secretoras de Insulina/metabolismo , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/enzimologia , Fenilbutiratos/farmacologia , Ratos , Ratos Wistar , Marcadores de Spin , Superóxidos/análise , Ácido Tauroquenodesoxicólico/farmacologiaRESUMO
Recently, missense and truncating mutations in the gene PCDH19 have been reported to cause female-restricted epilepsy with mental retardation (EFMR). EFMR (MIM#300088) is an X-linked disorder characterized by early onset seizures and intellectual disability (ID). Interestingly, unlike typical X-linked mode of inheritance, the phenotype is restricted to females, and males are unaffected carriers. PCDH19 is highly expressed in brain, and the encoded protein belongs to the cadherin superfamily. Here we report two unrelated female patients with deletions spanning PCDH19 identified by copy number variation (CNV) analysis and validated by qPCR. In one, we have identified a 3 Mb interstitial deletion at Xq21.33-q22.1 which spans PCDH19, LOC442459 & TNMD. This patient had her first seizure at 8 months old, and also has ID and aggressive behavior. In another female patient we identified a de novo 603 kb heterozygous deletion in a female patient with fits (since 1 year of age), ID, hyperactivity and aggressive behavior. The deletion spans the entire PCDH19 gene (also TNMD, SRPX2, TSPAN6 and SYTL4). In conclusion, our results suggest that deletions at PCDH19 also cause EFMR.
Assuntos
Anormalidades Múltiplas/genética , Caderinas/genética , Doenças Genéticas Ligadas ao Cromossomo X/genética , Deficiência Intelectual/genética , Convulsões/genética , Deleção de Sequência/genética , Variações do Número de Cópias de DNA , Feminino , Humanos , Análise em Microsséries , Protocaderinas , Reação em Cadeia da Polimerase em Tempo Real , Inativação do Cromossomo X/genéticaRESUMO
A 19-year-old male patient presented with progressive myoclonic seizures and speech disorder. The patient had photosensitivity, a few episodes of sudden transient blindness, and infrequent complex visual auras, dysarthria and mild ataxia, frequent myoclonic jerks prominently in the legs and severe dementia. Microscopic examination of the axillary skin biopsy revealed periodic acid-Schiff positive inclusion bodies in abluminal side of the apocrine sweat gland acini. Molecular screening showed a homozygous R241X mutation in EPM2A. Genotyping helps in the correct diagnosis of the Lafora disease (LD), which may be difficult to diagnose based on the available histopathological testing only. Our study is an effort to determine the distribution of mutations in LD patients in our region.
Assuntos
Doença de Lafora/diagnóstico , Doença de Lafora/patologia , Substituição de Aminoácidos/genética , Ataxia/diagnóstico , Demência/diagnóstico , Genética , Genótipo , Humanos , Doença de Lafora/genética , Masculino , Mutação de Sentido Incorreto , Transtornos de Fotossensibilidade/diagnóstico , Proteínas Tirosina Fosfatases não Receptoras/genética , Convulsões/diagnóstico , Distúrbios da Fala/diagnóstico , Adulto JovemAssuntos
Corpos de Inclusão/enzimologia , Fibras Musculares Esqueléticas/metabolismo , Músculo Esquelético/metabolismo , Adenosina Trifosfatases/metabolismo , Animais , Fosfatases de Especificidade Dupla/deficiência , Glucanos/metabolismo , Glicogênio/metabolismo , Camundongos , Camundongos Knockout , Fibras Musculares Esqueléticas/classificação , Músculo Esquelético/citologiaRESUMO
Deficiency of the urea cycle enzyme carbamylphosphate synthetase 1 (CPS1) causes hyperammonemia with a vast range of clinical severity from neonatal onset with early lethality to onset after age 40 with rare episodes of hyperammonemic confusion. The cause for this variability is not understood. We report two patients from one family with highly divergent clinical course, one presenting neonatally with a fatal form and the other at age 45 with benign diet-responsive disease. The patients are compound heterozygous for two mutations of the CPS1 gene, c.3558 + 1G > C and c.4101 + 2T > C. The haplotypes containing each mutation are identical between the two patients, as are the sequences of CPS1 exons and flanking introns. Transcriptional experiments show that the abnormal CPS1 transcripts generated by both mutations are identical in these two patients. We characterize promoter and enhancer sequences of the CPS1 gene and find also in these regions no sequence differences between patients. Finally, we perform cloning experiments and find that in the neonatal-onset case, clones of messenger RNA (mRNA) expressed from the allele carrying the c.4101 + 2T > C mutation are threefold more than clones of mRNA from the allele with the c.3558 + 1G > C mutation, whereas in the adult-onset case the two types of clones are equal, indicating skewed expression towards the c.4101 + 2T > C allele in the neonatal case. Although we are yet to understand the mechanism of this differential expression, our work suggests that allelic imbalance may explain clinical variability in CPS1 deficiency in some families.
Assuntos
Alelos , Doença da Deficiência da Carbamoil-Fosfato Sintase I/genética , Regulação da Expressão Gênica , Variação Genética , Sequência de Bases , Criança , Células Clonais , Clonagem Molecular , DNA Complementar/genética , Eletroforese em Gel de Ágar , Elementos Facilitadores Genéticos/genética , Éxons/genética , Família , Feminino , Haplótipos/genética , Humanos , Masculino , Pessoa de Meia-Idade , Dados de Sequência Molecular , Linhagem , FenótipoAssuntos
Autofagia/genética , Mapeamento Cromossômico , Doenças Genéticas Ligadas ao Cromossomo X/genética , Doenças Musculares/genética , Eletromiografia , Genes Recessivos , Doenças Genéticas Ligadas ao Cromossomo X/patologia , Doenças Genéticas Ligadas ao Cromossomo X/fisiopatologia , Humanos , Masculino , Fibras Musculares Esqueléticas/patologia , Doenças Musculares/patologia , Doenças Musculares/fisiopatologia , LinhagemRESUMO
Lafora disease (LD) is the most severe form of Progressive Myoclonus Epilepsy with teenage onset. It has an autosomal recessive mode of inheritance and is almost universally fatal by the second or third decade of life. To date, there is no prevention or cure. In the last decade, with the identification of the genes responsible for this disease, much knowledge has been gained with the potential for the future development of effective treatment. This review will briefly address clinical issues and will focus on the molecular aspects of the disease.
Assuntos
Doença de Lafora/fisiopatologia , Adolescente , Idade de Início , Criança , Genótipo , Humanos , Doença de Lafora/genética , Doença de Lafora/metabolismo , Doença de Lafora/patologia , Glicoproteínas de Membrana/genética , FenótipoRESUMO
BACKGROUND: Despite advances in the characterisation of mutations in the MECP2-coding region, a small proportion of classic RTT cases remain without recognisable mutations. OBJECTIVE AND METHODS: To identify previously unknown mutations, a quantitative assay was established, providing estimates of MECP2_e1 and MECP2_e2 expression levels in peripheral blood. A systematic analysis of an Israeli cohort of 82 patients with classic and atypical RTT is presented, including sequence analysis of the MECP2-coding region, MLPA, XCI and quantitative expression assays. RESULTS AND CONCLUSION: A novel mis-sense mutation at ca 453C-->T (pD151E), resulting in a change of a conserved residue at the methyl-binding domain, and a rare GT deletion of intron 1 donor splice site are reported. It is shown that various MECP2 mutations had distinct effects on MECP2 expression levels in peripheral blood. The most significant (p<0.001) reduction in the expression of both MECP2 isoforms was related to the presence of the intron 1 donor splice-site mutation. Using quantitative expression assays, it was shown that several patients with classic and atypical RTT with no mutation findings had significantly lower MECP2 expression levels. Further research on these patients may disclose still elusive non-coding regulatory MECP2 mutations.
Assuntos
Proteína 2 de Ligação a Metil-CpG/genética , Síndrome de Rett/genética , Cromossomos Humanos X , Estudos de Coortes , Sequência Conservada , DNA/genética , DNA/isolamento & purificação , Feminino , Regulação da Expressão Gênica , Humanos , Israel , Masculino , Mutação de Sentido Incorreto , Polimorfismo de Nucleotídeo Único , Isoformas de Proteínas/genética , RNA/genética , RNA/isolamento & purificaçãoRESUMO
Lafora disease (LD) can be diagnosed by skin biopsy, but this approach has both false negatives and false positives. Biopsies of other organs can also be diagnostic but are more invasive. Genetic diagnosis is also possible but can be inconclusive, for example, in patients with only one heterozygous EPM2A mutation and patients with apparently homozygous EPM2B mutations where one parent is not a carrier of the mutation. We sought to identify occult mutations and clarify the genotypes and confirm the diagnosis of LD in patients with apparent nonrecessive disease inheritance. We used single nucleotide polymorphism, quantitative PCR, and fluorescent in situ hybridization analyses. We identified large EPM2A and EPM2B deletions undetectable by PCR in the heterozygous state and describe simple methods for their routine detection. We report a coding sequence change in several patients and describe why the pathogenic role of this change remains unclear. We confirm that adult-onset LD is due to EPM2B mutations. Finally, we report major intrafamilial heterogeneity in age at onset in LD.
Assuntos
Proteínas de Transporte/genética , Erros de Diagnóstico/prevenção & controle , Predisposição Genética para Doença/genética , Doença de Lafora/diagnóstico , Doença de Lafora/genética , Adolescente , Adulto , Idade de Início , Sequência de Bases/genética , Mapeamento Cromossômico/métodos , Análise Mutacional de DNA/métodos , Feminino , Ligação Genética/genética , Marcadores Genéticos/genética , Genótipo , Heterozigoto , Humanos , Hibridização in Situ Fluorescente/métodos , Doença de Lafora/fisiopatologia , Masculino , Mutação/genética , Linhagem , Reação em Cadeia da Polimerase/métodos , Polimorfismo de Nucleotídeo Único/genética , Proteínas Tirosina Fosfatases/genética , Proteínas Tirosina Fosfatases não Receptoras , Ubiquitina-Proteína LigasesRESUMO
BACKGROUND: Despite advances in the characterisation of mutations in the MECP2-coding region, a small proportion of classic RTT cases remain without recognisable mutations. OBJECTIVE AND METHODS: To identify previously unknown mutations, a quantitative assay was established, providing estimates of MECP2_e1 and MECP2_e2 expression levels in peripheral blood. A systematic analysis of an Israeli cohort of 82 patients with classic and atypical RTT is presented, including sequence analysis of the MECP2-coding region, MLPA, XCI and quantitative expression assays. RESULTS AND CONCLUSION: A novel mis-sense mutation at ca 453C-->T (pD151E), resulting in a change of a conserved residue at the methyl-binding domain, and a rare GT deletion of intron 1 donor splice site are reported. It is shown that various MECP2 mutations had distinct effects on MECP2 expression levels in peripheral blood. The most significant (p<0.001) reduction in the expression of both MECP2 isoforms was related to the presence of the intron 1 donor splice-site mutation. Using quantitative expression assays, it was shown that several patients with classic and atypical RTT with no mutation findings had significantly lower MECP2 expression levels. Further research on these patients may disclose still elusive non-coding regulatory MECP2 mutations.
Assuntos
Expressão Gênica/genética , Proteína 2 de Ligação a Metil-CpG/genética , Mutação/genética , Síndrome de Rett/genética , Adolescente , Adulto , Criança , Pré-Escolar , Estudos de Coortes , Análise Mutacional de DNA/métodos , Humanos , Israel , Proteína 2 de Ligação a Metil-CpG/sangue , Proteína 2 de Ligação a Metil-CpG/deficiência , Reprodutibilidade dos Testes , Síndrome de Rett/diagnóstico , Síndrome de Rett/metabolismo , Inativação do Cromossomo XAssuntos
Predisposição Genética para Doença/genética , Alucinações/tratamento farmacológico , Alucinações/etiologia , Doença de Lafora/complicações , Doença de Lafora/tratamento farmacológico , Adulto , Anticonvulsivantes/uso terapêutico , Antipsicóticos/uso terapêutico , Encéfalo/efeitos dos fármacos , Encéfalo/fisiopatologia , Proteínas de Transporte/genética , Dibenzotiazepinas/uso terapêutico , Progressão da Doença , Eletroencefalografia , Feminino , Alucinações/fisiopatologia , Humanos , Doença de Lafora/fisiopatologia , Mutação/genética , Fumarato de Quetiapina , Convulsões/complicações , Convulsões/tratamento farmacológico , Convulsões/etiologia , Resultado do Tratamento , Ubiquitina-Proteína LigasesAssuntos
Doenças Genéticas Ligadas ao Cromossomo X/diagnóstico , Doenças Genéticas Ligadas ao Cromossomo X/fisiopatologia , Músculo Esquelético/fisiopatologia , Doenças Musculares/diagnóstico , Doenças Musculares/fisiopatologia , Adulto , Autofagia/genética , Análise Mutacional de DNA , Diagnóstico Diferencial , Progressão da Doença , Eletromiografia , Eletrofisiologia , Feminino , Doenças Genéticas Ligadas ao Cromossomo X/genética , Predisposição Genética para Doença/genética , Testes Genéticos , Genótipo , Haplótipos , Humanos , Masculino , Pessoa de Meia-Idade , Fibras Musculares Esqueléticas/metabolismo , Fibras Musculares Esqueléticas/patologia , Músculo Esquelético/metabolismo , Músculo Esquelético/patologia , Doenças Musculares/genética , Penetrância , Fenótipo , Valor Preditivo dos Testes , Sarcolema/genética , Sarcolema/metabolismo , SíndromeRESUMO
Lafora disease (LD) is the most common teenage-onset progressive myoclonus epilepsy. It is caused by recessive mutations in the EPM2A or EPM2B genes. The authors describe a family with three affected members with no mutations in either gene. Linkage and haplotype analyses exclude both loci from causative involvement in this family. Therefore, a third LD locus is predicted. Its identification will be a crucial element in the understanding of the biochemical pathway underlying the generation of Lafora bodies and LD.
Assuntos
Doença de Lafora/genética , Adolescente , Adulto , Criança , Consanguinidade , Análise Mutacional de DNA , Genes Recessivos , Heterogeneidade Genética , Ligação Genética , Glicogênio/metabolismo , Haplótipos/genética , Humanos , Repetições de Microssatélites , Paquistão/etnologia , LinhagemRESUMO
Lafora disease is characterized by pathognomonic inclusions, Lafora bodies (LB), in neurons and other cell types. In skin, LB have been reported in either eccrine sweat glands or in apocrine sweat glands. The disease is caused by mutations in either the EPM2A gene or in a second yet-unknown gene. Here the authors determine whether a genotype-phenotype correlation exists between the genetic form of the disease and the skin cell type affected by LB formation. Also is described an important source of false positivity in the use of axillary biopsies for disease diagnosis.
Assuntos
Doença de Lafora/diagnóstico , Pele/patologia , Adolescente , Criança , Reações Falso-Positivas , Feminino , Genótipo , Humanos , Doença de Lafora/genética , Doença de Lafora/patologia , Linhagem , Fenótipo , Proteínas Tirosina Fosfatases/genética , Proteínas Tirosina Fosfatases não Receptoras , Pele/citologiaAssuntos
Antifúngicos/farmacologia , Fungos/efeitos dos fármacos , Fusarium/efeitos dos fármacos , Scedosporium/efeitos dos fármacos , Tiazóis/farmacologia , Triazóis/farmacologia , Anfotericina B/farmacologia , Itraconazol/farmacologia , Testes de Sensibilidade Microbiana , Pirimidinas/farmacologia , VoriconazolRESUMO
BACKGROUND: Lafora disease is a progressive myoclonus epilepsy with polyglucosan accumulations and a peculiar neurodegeneration with generalised organellar disintegration. It causes severe seizures, leading to dementia and eventually death in early adulthood. METHODS: One Lafora disease gene, EPM2A, has been identified on chromosome 6q24. Locus heterogeneity led us to search for a second gene using a genome wide linkage scan in French-Canadian families. RESULTS: We mapped a second Lafora disease locus, EPM2B, to a 2.2 Mb region at 6p22, a region known to code for several proteins, including kinesins. Kinesins are microtubule dependent motor proteins that are involved in transporting cellular components. In neurones, they play a major role in axonal and dendritic transport. CONCLUSION: Analysis of the present locus in other non-EPM2A families will reveal whether there is further locus heterogeneity. Identification of the disease gene will be of major importance towards our understanding of the pathogenesis of Lafora disease.
Assuntos
Cromossomos Humanos Par 6/genética , Doença de Lafora/genética , Mapeamento Cromossômico/métodos , Saúde da Família , Feminino , Haplótipos , Humanos , Doença de Lafora/patologia , Escore Lod , Masculino , Repetições de Microssatélites , LinhagemRESUMO
BACKGROUND: X-Linked myopathy with excessive autophagy (XMEA) is a childhood-onset slowly progressive disease of skeletal muscle with no cardiac, nervous system, or other organ involvement. Pathology is distinctive: membrane-bound autophagic vacuoles, multifold reduplication of the basement membrane, and intense deposition of membrane attack complex and calcium at the myofiber surface. XMEA has been linked to the most telomeric 10.5 cM of Xq28. The authors now report identification of new families, refinement of the locus, mapping of genes to the region, and screening of candidate genes for mutations. METHODS AND RESULTS: Seven new families were ascertained, including an American family with XMEA. Using 11 new microsatellite genetic markers, the authors fine-mapped a recombination in this family and a common ancestral haplotype in two French families, which localized the gene in a 4.37-Mb region. Sequence data were assembled from public and private databases and a near-continuous sequence derived for the entire region. With this sequence, a gene map of 82 genes and 28 expressed sequence tag clusters was constructed; to date, 12 candidate genes have been screened for mutations. CONCLUSIONS: This study doubles the number of reported families with XMEA and more firmly establishes its distinctive clinicopathologic features. It also advances the search for the XMEA causative defect by reducing the disease locus to approximately half its previous size, assembling an almost complete sequence of the refined region, identifying all known genes in this sequence, and excluding the presence of mutations in 10% of these genes.