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1.
Nat Commun ; 12(1): 1160, 2021 02 19.
Artigo em Inglês | MEDLINE | ID: mdl-33608547

RESUMO

Glia engulf and phagocytose neurons during neural circuit developmental remodeling. Disrupting this pruning process contributes to Fragile X syndrome (FXS), a leading cause of intellectual disability and autism spectrum disorder in mammals. Utilizing a Drosophila FXS model central brain circuit, we identify two glial classes responsible for Draper-dependent elimination of developmentally transient PDF-Tri neurons. We find that neuronal Fragile X Mental Retardation Protein (FMRP) drives insulin receptor activation in glia, promotes glial Draper engulfment receptor expression, and negatively regulates membrane-molding ESCRT-III Shrub function during PDF-Tri neuron clearance during neurodevelopment in Drosophila. In this context, we demonstrate genetic interactions between FMRP and insulin receptor signaling, FMRP and Draper, and FMRP and Shrub in PDF-Tri neuron elimination. We show that FMRP is required within neurons, not glia, for glial engulfment, indicating FMRP-dependent neuron-to-glia signaling mediates neuronal clearance. We conclude neuronal FMRP drives glial insulin receptor activation to facilitate Draper- and Shrub-dependent neuronal clearance during neurodevelopment in Drosophila.


Assuntos
Proteínas de Drosophila/metabolismo , Proteína do X Frágil de Retardo Mental/metabolismo , Neuroglia/metabolismo , Neurônios/fisiologia , Neuropeptídeos/metabolismo , Receptor de Insulina/metabolismo , Animais , Antígenos CD , Transtorno do Espectro Autista/genética , Transtorno do Espectro Autista/metabolismo , Sistema Nervoso Central/metabolismo , Drosophila/metabolismo , Proteínas de Drosophila/genética , Proteína do X Frágil de Retardo Mental/genética , Síndrome do Cromossomo X Frágil/genética , Neuropeptídeos/genética , Transdução de Sinais
2.
Nat Commun ; 12(1): 1265, 2021 02 24.
Artigo em Inglês | MEDLINE | ID: mdl-33627639

RESUMO

Fragile X-associated tremor/ataxia syndrome (FXTAS) is an incurable neurodegenerative disorder caused by expansion of CGG repeats in the FMR1 5'UTR. The RNA containing expanded CGG repeats (rCGGexp) causes cell damage by interaction with complementary DNA, forming R-loop structures, sequestration of nuclear proteins involved in RNA metabolism and initiation of translation of polyglycine-containing protein (FMRpolyG), which forms nuclear insoluble inclusions. Here we show the therapeutic potential of short antisense oligonucleotide steric blockers (ASOs) targeting directly the rCGGexp. In nuclei of FXTAS cells ASOs affect R-loop formation and correct miRNA biogenesis and alternative splicing, indicating that nuclear proteins are released from toxic sequestration. In cytoplasm, ASOs significantly decrease the biosynthesis and accumulation of FMRpolyG. Delivery of ASO into a brain of FXTAS mouse model reduces formation of inclusions, improves motor behavior and corrects gene expression profile with marginal signs of toxicity after a few weeks from a treatment.


Assuntos
Ataxia/metabolismo , Proteína do X Frágil de Retardo Mental/metabolismo , Síndrome do Cromossomo X Frágil/metabolismo , Oligonucleotídeos Antissenso/metabolismo , Tremor/metabolismo , Expansão das Repetições de Trinucleotídeos/genética , Expansão das Repetições de Trinucleotídeos/fisiologia , Processamento Alternativo/genética , Processamento Alternativo/fisiologia , Animais , Ataxia/genética , Éxons/genética , Feminino , Proteína do X Frágil de Retardo Mental/genética , Síndrome do Cromossomo X Frágil/genética , Masculino , Camundongos , Camundongos Transgênicos , MicroRNAs/genética , MicroRNAs/metabolismo , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Oligonucleotídeos Antissenso/genética , Tremor/genética
3.
Nat Cell Biol ; 23(1): 40-48, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33420492

RESUMO

Loss of the fragile X protein FMRP is a leading cause of intellectual disability and autism1,2, but the underlying mechanism remains poorly understood. We report that FMRP deficiency results in hyperactivated nonsense-mediated mRNA decay (NMD)3,4 in human SH-SY5Y neuroblastoma cells and fragile X syndrome (FXS) fibroblast-derived induced pluripotent stem cells (iPSCs). We examined the underlying mechanism and found that the key NMD factor UPF1 binds directly to FMRP, promoting FMRP binding to NMD targets. Our data indicate that FMRP acts as an NMD repressor. In the absence of FMRP, NMD targets are relieved from FMRP-mediated translational repression so that their half-lives are decreased and, for those NMD targets encoding NMD factors, increased translation produces abnormally high factor levels despite their hyperactivated NMD. Transcriptome-wide alterations caused by NMD hyperactivation have a role in the FXS phenotype. Consistent with this, small-molecule-mediated inhibition of hyperactivated NMD, which typifies iPSCs derived from patients with FXS, restores a number of neurodifferentiation markers, including those not deriving from NMD targets. Our mechanistic studies reveal that many molecular abnormalities in FMRP-deficient cells are attributable-either directly or indirectly-to misregulated NMD.


Assuntos
Proteína do X Frágil de Retardo Mental/genética , Síndrome do Cromossomo X Frágil/patologia , Deleção de Genes , Neuroblastoma/patologia , Degradação do RNAm Mediada por Códon sem Sentido , Transcriptoma , Estudos de Casos e Controles , Células Cultivadas , Fibroblastos/metabolismo , Fibroblastos/patologia , Síndrome do Cromossomo X Frágil/genética , Síndrome do Cromossomo X Frágil/metabolismo , Humanos , Células-Tronco Pluripotentes Induzidas/metabolismo , Células-Tronco Pluripotentes Induzidas/patologia , Neuroblastoma/genética , Neuroblastoma/metabolismo , Neurônios/metabolismo , Neurônios/patologia , RNA-Seq , Transativadores
4.
Mol Cell ; 80(3): 381-383, 2020 11 05.
Artigo em Inglês | MEDLINE | ID: mdl-33157013

RESUMO

Recent work by Licznerski et al. suggests that mutant FMRP linked to Fragile-X syndrome elevates the inner mitochondrial membrane proton leak, leading to increased metabolism and changes in protein synthesis that trigger impaired synaptic maturation and autistic behaviors.


Assuntos
Síndrome do Cromossomo X Frágil , Trifosfato de Adenosina , Proteína do X Frágil de Retardo Mental/genética , Síndrome do Cromossomo X Frágil/genética , Humanos , Mitocôndrias/genética , Navios
5.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2845-2848, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018599

RESUMO

FRM1 premutation carriers exhibit various subtle deficits in balance and stability, prior to the development of the movement disorder Fragile X Associated Tremor/Ataxia Syndrome (FXTAS). Force plate posturography has increasingly been combined with the temporal sensitive imaging methods such as EEG to offer insight into the neural mechanisms which govern postural control. This study investigated cortical theta power during continuous balance and its relationship to balance performance in Fragile X premutation carriers. Eight premutation carriers and 6 controls stood on a force platform under altered sensory and cognitive conditions while postural sway and high-density EEG data were simultaneously recorded. Carriers exhibited greater sway area when sensory input was reduced (p=0.01) and cognitive load was increased (p=0.01), as well as significantly reduced frontal theta power compared to the Control Group. The relationship between theta power and postural control seen in the control group may indicate an increase in error detection caused by reduced visual input and greater discrepancies between expected and actual balance state. While the lower theta power in frontal regions of carriers may indicate a disruption in neural networks underpinning postural control. Such results provide new insight into the neural correlates of balance control in Fragile X premutation carriers.


Assuntos
Síndrome do Cromossomo X Frágil , Equilíbrio Postural , Ataxia/genética , Proteína do X Frágil de Retardo Mental , Síndrome do Cromossomo X Frágil/genética , Humanos , Tremor/genética
6.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2909-2912, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018615

RESUMO

Fragile X-associated Tremor/Ataxia Syndrome is a genetic neurodegenerative disorder affecting carriers of the FMR1 premutation. Not all carriers develop the condition and the age of onset is somewhat variable. A greater understanding of disease progression would be beneficial. Eight carriers and five controls matched by age, sex, and dominant hand volunteered to perform a sway task on a force platform while EEG was simultaneously recorded. Sway parameters were extracted from the movement data at important timepoints throughout their sway cycles and matched to their EEG activity. Distributed source analysis was applied. While there initially appeared to be differences in neural activity between the two groups in the anterior lobe, the right posterior lobe, the right superior parietal lobule and the right parietal lobe, these differences did not survive correction for multiple comparisons.


Assuntos
Proteína do X Frágil de Retardo Mental , Síndrome do Cromossomo X Frágil , Ataxia/genética , Proteína do X Frágil de Retardo Mental/genética , Síndrome do Cromossomo X Frágil/genética , Heterozigoto , Humanos , Tremor/genética
7.
Proc Natl Acad Sci U S A ; 117(40): 25092-25103, 2020 10 06.
Artigo em Inglês | MEDLINE | ID: mdl-32958647

RESUMO

The loss of fragile X mental retardation protein (FMRP) causes fragile X syndrome (FXS), the most common inherited intellectual disability. How the loss of FMRP alters protein expression and astroglial functions remains essentially unknown. Here we showed that selective loss of astroglial FMRP in vivo up-regulates a brain-enriched miRNA, miR-128-3p, in mouse and human FMRP-deficient astroglia, which suppresses developmental expression of astroglial metabotropic glutamate receptor 5 (mGluR5), a major receptor in mediating developmental astroglia to neuron communication. Selective in vivo inhibition of miR-128-3p in FMRP-deficient astroglia sufficiently rescues decreased mGluR5 function, while astroglial overexpression of miR-128-3p strongly and selectively diminishes developmental astroglial mGluR5 signaling. Subsequent transcriptome and proteome profiling further suggests that FMRP commonly and preferentially regulates protein expression through posttranscriptional, but not transcriptional, mechanisms in astroglia. Overall, our study defines an FMRP-dependent cell-autonomous miR pathway that selectively alters developmental astroglial mGluR5 signaling, unveiling astroglial molecular mechanisms involved in FXS pathogenesis.


Assuntos
Proteína do X Frágil de Retardo Mental/genética , Síndrome do Cromossomo X Frágil/genética , MicroRNAs/genética , Receptor de Glutamato Metabotrópico 5/genética , Animais , Astrócitos/metabolismo , Astrócitos/patologia , Modelos Animais de Doenças , Síndrome do Cromossomo X Frágil/patologia , Humanos , Camundongos , Neurônios/metabolismo , Transdução de Sinais/genética , Ativação Transcricional/genética
8.
Zhonghua Yi Xue Yi Chuan Xue Za Zhi ; 37(10): 1104-1107, 2020 Oct 10.
Artigo em Chinês | MEDLINE | ID: mdl-32924111

RESUMO

OBJECTIVE: To determine the carrier rate of Fragile X mental retardation 1 gene (FMR1) mutants in women with a history of adverse pregnancy or childbirth, and to provide prenatal diagnosis for the carriers. METHODS: Peripheral blood samples were collected from women with a history of adverse pregnancy or childbirth, and the FMR1 gene cytosine-guanine-guanine repeat number (CGG)n was determined by triple-repeat primer polymerase chain reaction (TP-PCR) combined with capillary electrophoresis. Prenatal diagnosis was provided for the carriers during pregnancy. RESULTS: Among 819 samples, 9 gray zone repeats carriers and 10 premutation carriers were detected, which gave a prevalence of 1 in 91 and 1 in 82, respectively, with a total prevalence of 1 in 43. Prenatal diagnosis was provided during 7 pregnancies for 6 carriers. A female fetus with premutation (n = 30/57) and an affected male fetus with full mutation (n = 336) were detected. CONCLUSION: FMR1 gene testing in women with a history of adverse pregnancy or childbirth can facilitate genetic counseling and reproductive guidance for carriers of gray zone repeats and premutations. Prenatal diagnosis for carriers of premutation can facilitate reduction of the birth of children with fragile X syndrome.


Assuntos
Proteína do X Frágil de Retardo Mental , Síndrome do Cromossomo X Frágil , Feminino , Proteína do X Frágil de Retardo Mental/genética , Síndrome do Cromossomo X Frágil/diagnóstico , Síndrome do Cromossomo X Frágil/genética , Testes Genéticos , Humanos , Masculino , Mutação , Gravidez , Diagnóstico Pré-Natal
9.
Nucleic Acids Res ; 48(14): 7856-7863, 2020 08 20.
Artigo em Inglês | MEDLINE | ID: mdl-32619224

RESUMO

The Fragile X-related disorders (FXDs) are Repeat Expansion Diseases, genetic disorders that result from the expansion of a disease-specific microsatellite. In those Repeat Expansion Disease models where it has been examined, expansion is dependent on functional mismatch repair (MMR) factors, including MutLγ, a heterodimer of MLH1/MLH3, one of the three MutL complexes found in mammals and a minor player in MMR. In contrast, MutLα, a much more abundant MutL complex that is the major contributor to MMR, is either not required for expansion or plays a limited role in expansion in many model systems. How MutLγ acts to generate expansions is unclear given its normal role in protecting against microsatellite instability and while MLH3 does have an associated endonuclease activity, whether that contributes to repeat expansion is uncertain. We show here, using a gene-editing approach, that a point mutation that eliminates the endonuclease activity of MLH3 eliminates expansions in an FXD mouse embryonic stem cell model. This restricts the number of possible models for repeat expansion and supports the idea that MutLγ may be a useful druggable target to reduce somatic expansion in those disorders where it contributes to disease pathology.


Assuntos
Síndrome do Cromossomo X Frágil/genética , Proteínas MutL/genética , Expansão das Repetições de Trinucleotídeos , Alelos , Animais , Linhagem Celular , Modelos Animais de Doenças , Masculino , Camundongos , Mutação Puntual , Domínios Proteicos/genética , Células-Tronco
10.
Proc Natl Acad Sci U S A ; 117(28): 16527-16536, 2020 07 14.
Artigo em Inglês | MEDLINE | ID: mdl-32601218

RESUMO

Folate deprivation drives the instability of a group of rare fragile sites (RFSs) characterized by CGG trinucleotide repeat (TNR) sequences. Pathological expansion of the TNR within the FRAXA locus perturbs DNA replication and is the major causative factor for fragile X syndrome, a sex-linked disorder associated with cognitive impairment. Although folate-sensitive RFSs share many features with common fragile sites (CFSs; which are found in all individuals), they are induced by different stresses and share no sequence similarity. It is known that a pathway (termed MiDAS) is employed to complete the replication of CFSs in early mitosis. This process requires RAD52 and is implicated in generating translocations and copy number changes at CFSs in cancers. However, it is unclear whether RFSs also utilize MiDAS and to what extent the fragility of CFSs and RFSs arises by shared or distinct mechanisms. Here, we demonstrate that MiDAS does occur at FRAXA following folate deprivation but proceeds via a pathway that shows some mechanistic differences from that at CFSs, being dependent on RAD51, SLX1, and POLD3. A failure to complete MiDAS at FRAXA leads to severe locus instability and missegregation in mitosis. We propose that break-induced DNA replication is required for the replication of FRAXA under folate stress and define a cellular function for human SLX1. These findings provide insights into how folate deprivation drives instability in the human genome.


Assuntos
Endodesoxirribonucleases/metabolismo , Ácido Fólico/metabolismo , Síndrome do Cromossomo X Frágil/metabolismo , Mitose , Rad51 Recombinase/metabolismo , DNA/genética , DNA/metabolismo , Reparo do DNA , Endodesoxirribonucleases/genética , Síndrome do Cromossomo X Frágil/genética , Síndrome do Cromossomo X Frágil/fisiopatologia , Humanos , Rad51 Recombinase/genética , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Proteína Rad52 de Recombinação e Reparo de DNA/metabolismo , Recombinases/genética , Recombinases/metabolismo
11.
Nat Commun ; 11(1): 2755, 2020 06 02.
Artigo em Inglês | MEDLINE | ID: mdl-32488011

RESUMO

Fragile X Syndrome results from a loss of Fragile X Mental Retardation Protein (FMRP). We now show that FMRP is a member of a Cav3-Kv4 ion channel complex that is known to regulate A-type potassium current in cerebellar granule cells to produce mossy fiber LTP. Mossy fiber LTP is absent in Fmr1 knockout (KO) mice but is restored by FMRP(1-297)-tat peptide. This peptide further rapidly permeates the blood-brain barrier to enter cells across the cerebellar-cortical axis that restores the balance of protein translation for at least 24 h and transiently reduces elevated levels of activity of adult Fmr1 KO mice in the Open Field Test. These data reveal that FMRP(1-297)-tat can improve function from the levels of protein translation to synaptic efficacy and behaviour in a model of Fragile X syndrome, identifying a potential therapeutic strategy for this genetic disorder.


Assuntos
Proteína do X Frágil de Retardo Mental/metabolismo , Síndrome do Cromossomo X Frágil/metabolismo , Canais Iônicos/metabolismo , Animais , Encéfalo/patologia , Modelos Animais de Doenças , Proteína do X Frágil de Retardo Mental/genética , Síndrome do Cromossomo X Frágil/genética , Síndrome do Cromossomo X Frágil/patologia , Masculino , Camundongos , Camundongos Knockout , Transtornos do Neurodesenvolvimento/genética , Transtornos do Neurodesenvolvimento/metabolismo , Transtornos do Neurodesenvolvimento/patologia , Plasticidade Neuronal/genética , Plasticidade Neuronal/fisiologia , Neurônios/metabolismo , Biossíntese de Proteínas
12.
Adv Neurobiol ; 25: 33-53, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32578143

RESUMO

Fragile X syndrome (FXS), the most common genetic form of autism spectrum disorder, is caused by deficiency of the fragile X mental retardation protein (FMRP). Despite extensive research using animal models, understanding how FMRP regulates human brain development and function remains a major challenge. Human pluripotent stem cells (hPSCs) offer powerful platforms for studying mechanisms of human diseases and for evaluating potential treatments. Genome editing, particularly the CRISPR/Cas9-based method, is highly effective for generating models to study genetic human diseases. Here we summarize how hPSCs and genome editing provide much-needed models for studying the genetic underpinnings, cellular mechanisms, and neuropathology that are unique to human FXS. The use of hPSCs and genome editing also provides an essential platform for therapeutic development in FXS.


Assuntos
Transtorno do Espectro Autista , Síndrome do Cromossomo X Frágil , Animais , Síndrome do Cromossomo X Frágil/genética , Síndrome do Cromossomo X Frágil/terapia , Edição de Genes , Humanos , Células-Tronco
13.
Adv Neurobiol ; 25: 207-218, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32578148

RESUMO

Neurodevelopmental disorders (ND) are characterized by an impairment of the nervous system during its development, with a wide variety of phenotypes based on genetic or environmental cues. There are currently several disorders grouped under ND including intellectual disabilities (ID), attention-deficit hyperactivity disorder (ADHD), and autism spectrum disorders (ASD). Although NDs can have multiple culprits with varied diagnostics, several NDs present an inflammatory component. Taking advantage of induced pluripotent stem cells (iPSC), several disorders were modeled in a dish complementing in vivo data from rodent models or clinical data. Monogenic syndromes displaying ND are more feasible to be modeled using iPSCs also due to the ability to recruit patients and clinical data available. Some of these genetic disorders are Fragile X Syndrome (FXS), Rett Syndrome (RTT), and Down Syndrome (DS). Environmental NDs can be caused by maternal immune activation (MIA), such as the infection with Zika virus during pregnancy known to cause neural damage to the fetus. Our goal in this chapter is to review the advances of using stem cell research in NDs, focusing on the role of neuroinflammation on ASD and environmental NDs studies.


Assuntos
Transtorno do Espectro Autista , Síndrome do Cromossomo X Frágil , Células-Tronco Pluripotentes Induzidas , Células-Tronco Pluripotentes , Infecção por Zika virus , Zika virus , Síndrome do Cromossomo X Frágil/genética , Humanos , Inflamação
14.
PLoS Genet ; 16(6): e1008902, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32589669

RESUMO

Expansion of a CGG-repeat tract in the 5' untranslated region of the FMR1 gene causes the fragile X-related disorders (FXDs; aka the FMR1 disorders). The expansion mechanism is likely shared by the 35+ other diseases resulting from expansion of a disease-specific microsatellite, but many steps in this process are unknown. We have shown previously that expansion is dependent upon functional mismatch repair proteins, including an absolute requirement for MutLγ, one of the three MutL heterodimeric complexes found in mammalian cells. We demonstrate here that both MutLα and MutLß, the two other MutL complexes present in mammalian cells, are also required for most, if not all, expansions in a mouse embryonic stem cell model of the FXDs. A role for MutLα and MutLß is consistent with human GWA studies implicating these complexes as modifiers of expansion risk in other Repeat Expansion Diseases. The requirement for all three complexes suggests a novel model in which these complexes co-operate to generate expansions. It also suggests that the PMS1 subunit of MutLß may be a reasonable therapeutic target in those diseases in which somatic expansion is an important disease modifier.


Assuntos
Síndrome do Cromossomo X Frágil/genética , Endonuclease PMS2 de Reparo de Erro de Pareamento/genética , Proteínas MutL/genética , Expansão das Repetições de Trinucleotídeos/genética , Animais , Linhagem Celular , Reparo de Erro de Pareamento de DNA , Modelos Animais de Doenças , Células-Tronco Embrionárias , Técnicas de Inativação de Genes , Humanos , Camundongos , Endonuclease PMS2 de Reparo de Erro de Pareamento/metabolismo , Proteínas MutL/metabolismo
15.
Hum Genet ; 139(12): 1531-1539, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32533363

RESUMO

The fragile X premutation is defined by the expansion of the CGG trinucleotide repeat at the 5' UTR of the FMR1 gene to between 55 and 200 repeats, while repeat tracks longer than 200 are defined as full mutations. Men carrying a premutation are at increased risk for fragile X-associated tremor/ataxia syndrome (FXTAS); those with > 200 repeats have fragile X syndrome, a common genetic form of intellectual disabilities. In our study, we tested the hypothesis that men carrying a fragile X premutation or full mutation are "biologically older", as suggested by the associated age-related disorder in the presence of the fragile X premutation or the altered cellular pathology that affects both the fragile X premutation and full mutation carriers. Thus, we predicted that both groups would have shorter telomeres than men carrying the normal size repeat allele. Using linear regression models, we found that, on average, premutation carriers had shorter telomeres compared with non-carriers (n = 69 vs n = 36; p = 0.02) and that there was no difference in telomere length between full mutation carriers and non-carriers (n = 37 vs n = 29; p > 0.10). Among premutation carriers only, we also asked whether telomere length was shorter among men with vs without symptoms of FXTAS (n = 28 vs n = 38 and n = 27 vs n = 41, depending on criteria) and found no evidence for a difference (p > 0.10). Previous studies have shown that the premutation is transcribed whereas the full mutation is not, and the expanded repeat track in FMR1 transcript is thought to lead to the risk for premutation-associated disorders. Thus, our data suggest that the observed premutation-only telomere shortening may be a consequence of the toxic effect of the premutation transcript and suggest that premutation carriers are "biologically older" than men carrying the normal size allele in the same age group.


Assuntos
Ataxia/genética , Proteína do X Frágil de Retardo Mental/genética , Síndrome do Cromossomo X Frágil/genética , Telômero/genética , Tremor/genética , Regiões 5' não Traduzidas/genética , Adulto , Idoso , Alelos , Ataxia/patologia , Síndrome do Cromossomo X Frágil/patologia , Humanos , Masculino , Pessoa de Meia-Idade , Mutação/genética , Telômero/patologia , Telômero/ultraestrutura , Homeostase do Telômero/genética , Tremor/patologia , Expansão das Repetições de Trinucleotídeos/genética , Adulto Jovem
16.
Gene ; 753: 144793, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32446918

RESUMO

BACKGROUND: Fragile X syndrome (FXS) is a monogenic disorder and a common cause of intellectual disability (ID). Up to now, very few pathological variants other than the typical CGG-repeat expansion have been reported in the FMR1 gene. METHODS: A panel of 56 intellectual disability (ID) genes including the FMR1 gene was sequenced in a cohort of 300 patients with unexplained ID. To determine the effect of a new FMR1 variant, total RNA from peripheral blood cells was reverse transcribed, amplified by polymerase chain reaction and sequenced. RESULTS: We report a novel G to A point variant (c.801G > A) located at the last nucleotide of exon 8 in the FMR1 gene in one patient with ID. Direct sequencing of the RT-PCR products revealed that the transcript from the allele with G to A variant skips exon 8 entirely, resulting in a joining of exons 7 and 9. Skipping of exon 8 may result in an abnormal FMR1 protein (FMRP), which removes the highly conserved region that encoding the KH1 domain of FMRP. CONCLUSIONS: This report describes for the first time that a synonymous variant in the FMR1 gene is associated with an error in mRNA processing, leading preferentially to the production of an aberrant transcript without exon 8. This splice variant was associated with an unspecific clinical presentation, suggesting the need for more detailed investigation of silent variants in ID patients with a large spectrum of phenotypes.


Assuntos
Proteína do X Frágil de Retardo Mental/genética , Síndrome do Cromossomo X Frágil/genética , Deficiência Intelectual/genética , Adolescente , Adulto , Alelos , Estudos de Coortes , Éxons , Humanos , Masculino , Mutação , Fenótipo , Polimorfismo de Nucleotídeo Único , Domínios Proteicos , Processamento de RNA , Análise de Sequência de RNA/métodos , Mutação Silenciosa , Expansão das Repetições de Trinucleotídeos
17.
J Neurosci ; 40(27): 5327-5340, 2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32467357

RESUMO

Channelopathies are implicated in Fragile X syndrome (FXS), yet the dysfunction of a particular ion channel varies with cell type. We previously showed that HCN channel function is elevated in CA1 dendrites of the fmr1 -/y mouse model of FXS, but reduced in L5 PFC dendrites. Using male mice, we tested whether Fragile X Mental Retardation Protein (FMRPO), the protein whose absence causes FXS, differentially modulates HCN channels in CA1 versus L5 PFC dendrites. Using a combination of viral tools, intracellular peptide, and dendritic electrophysiology, we found that FMRP regulates HCN channels via a cell-autonomous protein-protein interaction. Virally expressed FMRP restored WT HCN channel-related dendritic properties in both CA1 and L5 neurons. Rapid intracellular perfusion of the non-mRNA binding N-terminal fragment, FMRP1-298, similarly restored dendritic function. In support of a protein-protein interaction, we found that FMRP associated with HCN-TRIP8b complexes in both hippocampus and PFC. Finally, voltage-clamp recordings showed that FMRP modulated Ih by regulating the number of functional dendritic HCN channels rather than individual channel properties. Together, these represent three novel findings as to the nature of the changes in dendritic function in CA1 and PFC neurons based on the presence or absence of FMRP. Moreover, our findings provide evidence that FMRP can regulate its targets in opposite directions depending upon the cellular milieu.SIGNIFICANCE STATEMENT Changes in dendritic function, and voltage-gated ion channels in particular, are increasingly the focus of neurological disorders. We, and others, previously identified cell type-specific channelopathies in a mouse of model of Fragile X syndrome. The present study shows that replacing Fragile X Mental Retardation Protein, which is absent in Fragile X syndrome, in adult CA1 and L5 PFC neurons regulates the number of functional dendritic HCN channels in a cell type-specific manner. These results suggest that Fragile X Mental Retardation Protein regulates dendritic HCN channels via a cell-autonomous protein--protein mechanism.


Assuntos
Dendritos/fisiologia , Proteína do X Frágil de Retardo Mental/genética , Síndrome do Cromossomo X Frágil/genética , Hipocampo/fisiologia , Córtex Pré-Frontal/fisiologia , RNA Longo não Codificante/genética , Animais , Região CA1 Hipocampal/fisiopatologia , Dendritos/efeitos dos fármacos , Fenômenos Eletrofisiológicos , Feminino , Síndrome do Cromossomo X Frágil/fisiopatologia , Hipocampo/citologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Condução Nervosa/genética , Técnicas de Patch-Clamp , Fragmentos de Peptídeos/farmacologia , Córtex Pré-Frontal/citologia , RNA Longo não Codificante/fisiologia
18.
BMC Neurol ; 20(1): 145, 2020 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-32312236

RESUMO

BACKGROUND: Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late onset, X-linked genetic, neurodegenerative disorder caused by a "premutation (PM)" in the fragile X mental retardation 1 (FMR1) gene. Here we report a case of FXTAS from mainland of China who presented with rare orthostatic tremor. A review of tremor of FXTAS in the literature is also included. CASE PRESENTATION: A 67-year-old right-handed farmer started with tremor of both legs 8 years ago which was present while standing but absent when sitting or lying and progressed with unsteady gait one and a half years ago. The brain MRI showed high intensity signal in the bilateral middle cerebellar peduncles (MCP) in T2-weighted and fluid-attenuated inversion recovery (FLAIR) images and gene test for premutation for FMR1 was positive with 101 CGG repeats. The patient met the the diagnosis of definite FXTAS. Clonazepam and topiramate were administered to control tremor. We reviewed the literature and identified 64 cases with detailed clinical and genetic information. Orthostatic tremor associated with FXTAS is very rare. We found 85.2% patients reported tremor,42.6% with intention tremor,36.1% with kinetic tremor,32.8% with rest tremor and 29.5% with posture tremor. 37.7% of patients who have tremor showed at least two types of tremor. There were 6 patients with isolated rest tremor. There was 2 patient with voice tremor and 6 with head tremor. We also found that 74.6% FXTAS patients had family history of FMR1 gene associated diseases including Fragile X syndrome (FXS), FXTAS or fragile X-associated primary ovarian insufficiency (FXPOI). CONCLUSIONS: Adding our data to the available literature suggests that orthostatic tremor could be a rare initial manifestation of FXTAS and the review will increasing our understanding the phenotype of tremor in FXTAS. Family history of FMR1 gene associated diseases might be an important clue to the diagnosis.


Assuntos
Ataxia , Síndrome do Cromossomo X Frágil , Tremor , Idoso , Anticonvulsivantes/uso terapêutico , Ataxia/diagnóstico , Ataxia/tratamento farmacológico , Ataxia/genética , Ataxia/fisiopatologia , Encéfalo/diagnóstico por imagem , Encéfalo/fisiopatologia , Clonazepam/uso terapêutico , Síndrome do Cromossomo X Frágil/diagnóstico , Síndrome do Cromossomo X Frágil/tratamento farmacológico , Síndrome do Cromossomo X Frágil/genética , Síndrome do Cromossomo X Frágil/fisiopatologia , Humanos , Imagem por Ressonância Magnética , Masculino , Topiramato/uso terapêutico , Tremor/diagnóstico , Tremor/tratamento farmacológico , Tremor/genética , Tremor/fisiopatologia
19.
J Genet ; 992020.
Artigo em Inglês | MEDLINE | ID: mdl-32089525

RESUMO

The CGG repeats in the FMR1 gene expand in patients with fragile X syndrome, fragile X-associated tremour/ataxia syndrome and fragile X-associated primary ovarian failure. In this study, the CGG repeats in the FMR1 gene were studied in 449 males and 207 females using traditional polymerase chain reaction and triplet repeat primed PCR methods, also 18 CVS samples (six males and 12 females) were tested for prenatal diagnosis. Further, methylation sensitive multiplexed ligation dependent probe amplification was performed on some samples to confirm the results. Regarding the male patients, 1.1% and 9.7% had premutation (PM) and full mutation (FM) alleles, respectively. Also three (0.66%) male patients were mosaic for PM and FM alleles. Among females, 1.9% were GZ carriers and 5.8% were PM carriers. Prenatal diagnosis resulted in detection of two PM and one FM males as well as one FM carrier female. Our results were in concordance with the previously published results.


Assuntos
Proteína do X Frágil de Retardo Mental/genética , Síndrome do Cromossomo X Frágil/genética , Estudos de Associação Genética , Predisposição Genética para Doença , Deficiência Intelectual/genética , Insuficiência Ovariana Primária/genética , Repetições de Trinucleotídeos , Alelos , Feminino , Síndrome do Cromossomo X Frágil/diagnóstico , Humanos , Deficiência Intelectual/diagnóstico , Masculino , Tipagem de Sequências Multilocus , Insuficiência Ovariana Primária/diagnóstico
20.
Nat Neurosci ; 23(3): 386-397, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32066985

RESUMO

Repeat-associated non-AUG-initiated translation of expanded CGG repeats (CGG RAN) from the FMR1 5'-leader produces toxic proteins that contribute to neurodegeneration in fragile X-associated tremor/ataxia syndrome. Here we describe how unexpanded CGG repeats and their translation play conserved roles in regulating fragile X protein (FMRP) synthesis. In neurons, CGG RAN acts as an inhibitory upstream open reading frame to suppress basal FMRP production. Activation of mGluR5 receptors enhances FMRP synthesis. This enhancement requires both the CGG repeat and CGG RAN initiation sites. Using non-cleaving antisense oligonucleotides (ASOs), we selectively blocked CGG RAN. This ASO blockade enhanced endogenous FMRP expression in human neurons. In human and rodent neurons, CGG RAN-blocking ASOs suppressed repeat toxicity and prolonged survival. These findings delineate a native function for CGG repeats and RAN translation in regulating basal and activity-dependent FMRP synthesis, and they demonstrate the therapeutic potential of modulating CGG RAN translation in fragile X-associated disorders.


Assuntos
Expansão das Repetições de DNA/genética , Proteína do X Frágil de Retardo Mental/genética , Síndrome do Cromossomo X Frágil/genética , Repetições de Trinucleotídeos/genética , Animais , Linhagem Celular , Sobrevivência Celular/genética , Feminino , Proteína do X Frágil de Retardo Mental/biossíntese , Células-Tronco Pluripotentes Induzidas , Masculino , Camundongos , Neurônios/metabolismo , Oligonucleotídeos Antissenso/farmacologia , Biossíntese de Proteínas , Ratos , Ratos Long-Evans , Ratos Sprague-Dawley , Receptor de Glutamato Metabotrópico 5/biossíntese , Receptor de Glutamato Metabotrópico 5/genética
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