Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004352 (autism)
 32,579 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rett syndrome is an autism spectrum disorder caused by mosaic expression of mutant copies of the X-linked MECP2 gene in neurons. However, neurons do not die, which suggests that this is not a neurodegenerative disorder. An important question for future therapeutic approaches to this and related disorders concerns phenotypic reversibility. Can viable but defective neurons be repaired, or is the damage done during development without normal MeCP2 irrevocable? Using a mouse model, we demonstrate robust phenotypic reversal, as activation of MeCP2 expression leads to striking loss of advanced neurological symptoms in both immature and mature adult animals.
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PMID:Reversal of neurological defects in a mouse model of Rett syndrome. 1728 41

Turner syndrome (TS) is a developmental disorder most frequently arising from the loss of a complete X chromosome (karyotype 45,XO). The disorder is characterised by physiological abnormalities (notably short stature and ovarian dysfunction), emotional anomalies (including heightened anxiety) and by a neuropsychological profile encompassing deficits in visuospatial skills, memory, attention, social cognition and emotion recognition. Moreover, TS subjects are at significantly increased risk of developing attention deficit hyperactivity disorder (ADHD) and autism. At the neuroanatomical level, TS subjects display abnormalities across a number of brain structures, including the amygdala, hippocampus and orbitofrontal cortex. The TS phenotype arises due to reduced dosage of X-linked genes, and may also be modulated by parental origin of the single X chromosome. In this review, we discuss the utility of a mouse model of TS, the 39,XO mouse, in which the parental origin of the single X chromosome can be varied. This model provides the opportunity to investigate the effects of X-linked gene dosage/parent-of-origin effects on neurobiology in the absence of gross physiological abnormalities. Initial findings indicate that several features of the TS behavioural phenotype may be accurately recapitulated in the mouse. Furthermore, as X-linked gene dosage/imprinting can influence sex-specific neurobiology, investigations in the 39,XO mouse are also likely to offer insights into why certain neuropsychiatric disorders (including ADHD and autism) affect the sexes differently.
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PMID:The 39,XO mouse as a model for the neurobiology of Turner syndrome and sex-biased neuropsychiatric disorders. 1736 75

Mutations in the coding sequence of the methyl-CpG-binding protein 2 gene (MECP2), which cause Rett syndrome (RTT), have been found in male and female autistic subjects without, however, a causal relation having unequivocally been established. In this study, the MECP2 gene was scanned in a Portuguese autistic population, hypothesizing that the phenotypic spectrum of mutations extends beyond the traditional diagnosis of RTT and X-linked mental retardation, leading to a non-lethal phenotype in male autistic patients. The coding region, exon-intron boundaries, and the whole 3'UTR were scanned in 172 patients and 143 controls, by Detection of Virtually All Mutations-SSCP (DOVAM-S). Exon 1 was sequenced in 103 patients. We report 15 novel variants, not found in controls: one missense, two intronic, and 12 in the 3'UTR (seven in conserved nucleotides). The novel missense change, c.617G > C (p.G206A), was present in one autistic male with severe mental retardation and absence of language, and segregates in his maternal family. This change is located in a highly conserved residue within a region involved in an alternative transcriptional repression pathway, and likely alters the secondary structure of the MeCP2 protein. It is therefore plausible that it leads to a functional modification of MeCP2. MECP2 mRNA levels measured in four patients with 3'UTR conserved changes were below the control range, suggesting an alteration in the stability of the transcripts. Our results suggest that MECP2 can play a role in autism etiology, although very rarely, supporting the notion that MECP2 mutations underlie several neurodevelopmental disorders.
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PMID:MECP2 coding sequence and 3'UTR variation in 172 unrelated autistic patients. 1742 93

Mutations in MECP2, encoding methyl CpG binding protein 2 (MeCP2), cause most cases of Rett syndrome (RTT), an X-linked neurodevelopmental disorder. Both RTT and autism are "pervasive developmental disorders" and share a loss of social, cognitive and language skills and a gain in repetitive stereotyped behavior, following apparently normal perinatal development. Although MECP2 coding mutations are a rare cause of autism, MeCP2 expression defects were previously found in autism brain. To further study the role of MeCP2 in autism spectrum disorders (ASDs), we determined the frequency of MeCP2 expression defects in brain samples from autism and other ASDs. We also tested the hypotheses that MECP2 promoter mutations or aberrant promoter methylation correlate with reduced expression in cases of idiopathic autism. MeCP2 immunofluorescence in autism and other neurodevelopmental disorders was quantified by laser scanning cytometry and compared with control postmortem cerebral cortex samples on a large tissue microarray. A significant reduction in MeCP2 expression compared to age-matched controls was found in 11/14 autism (79%), 9/9 RTT (100%), 4/4 Angelman syndrome (100%), 3/4 Prader-Willi syndrome (75%), 3/5 Down syndrome (60%), and 2/2 attention deficit hyperactivity disorder (100%) frontal cortex samples. One autism female was heterozygous for a rare MECP2 promoter variant that correlated with reduced MeCP2 expression. A more frequent occurrence was significantly increased MECP2 promoter methylation in autism male frontal cortex compared to controls. Furthermore, percent promoter methylation of MECP2 significantly correlated with reduced MeCP2 protein expression. These results suggest that both genetic and epigenetic defects lead to reduced MeCP2 expression and may be important in the complex etiology of autism.
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PMID:Reduced MeCP2 expression is frequent in autism frontal cortex and correlates with aberrant MECP2 promoter methylation. 1748 79

Rett syndrome (RS) is an X-linked neurodevelopmental disorder and the second most common cause of genetic mental retardation in females. Different mutations in MECP2 are found in up to 95% of typical cases of RS. This mainly neuronal expressed gene functions as a major transcription repressor. Extensive studies on girls who have RS and mouse models are aimed at finding main gene targets for MeCP2 protein and defining neuropathologic changes caused by its defects. Studies comparing autistic features in RS with idiopathic autism and mentally retarded patients are presented. Decreased dendritic arborization is common to RS and autism, leading to further research on similarities in pathogenesis, including MeCP2 protein levels in autistic brains and MeCP2 effects on genes connected to autism, like DLX5 and genes on 15q11-13 region. This area also is involved in Angelman syndrome, which has many similarities to RS. Despite these connections, MECP2 mutations in nonspecific autistic and mentally retarded populations are rare.
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PMID:Rett syndrome. 1756 89

Duchenne and Becker muscular dystrophy are allelic X-linked disorders causing progressive muscle weakness in males. Duchenne muscular dystrophy is caused by absence of dystrophin in muscle and brain; boys with Duchenne muscular dystrophy have a static cognitive impairment with mean Full Scale IQ approximately 1 standard deviation below the mean. Less is known of the cognitive profile of males with Becker muscular dystrophy, which is associated with variable alterations in the amount or size of the dystrophin protein. The aim of this study was to describe the cognitive and psychological profile of males with Becker muscular dystrophy. This was a prospective cohort study. Clinical data collected included age at diagnosis and assessment, socioeconomic status, serum creatine kinase level, and site of gene deletion/mutation (by exon number). The following psychological tests were used to assess general intellectual functioning, academic achievement, incidence and nature of behavioral problems: The Wechsler Intelligence Scales, The Wide Range Achievement Test-Revised, The Developmental Test of Visual-Motor Integration, The Child Behavior Checklist, and The Conner's Parent Rating Scale. Twenty-four males were enrolled. The Wechsler Full Scale IQ was normally distributed with a mean of 95.6 (SD 23.3), which did not differ significantly from the population mean. The frequency of learning difficulties for reading was 21%, for spelling was 32%, and for arithmetic was 26%, significantly higher than the frequency in the general population. The frequency of total behavioral problems in the clinical range was 67%, and the frequency of autism was 8.3%. Patients with Becker muscular dystrophy demonstrate a less homogeneous cognitive phenotype than that seen in Duchenne muscular dystrophy. Males with Becker muscular dystrophy have a high incidence of learning difficulties. Autism and behavioral and attention problems are also more common in Becker muscular dystrophy than in the general population.
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PMID:Cognitive and psychological profile of males with Becker muscular dystrophy. 1805 90

Rett syndrome is an X-linked dominant neurodevelopmental disorder. Mutation of the methyl-CpG-binding protein 2 gene (MECP2) is present in up to 96% of patients with Rett syndrome. Eight mutations represent the hotspot of MECP2 mutations (R106W, R133C, T158M, R168X, R255X, R270X, R294X, and R306C) in patients with classic Rett syndrome. The prevalence and survival rate of Rett syndrome among Chinese women was investigated. The 8 hotspot mutations and the A140V mutation were also studied in 4 cohorts of Chinese children (n = 144) actively followed up in our university neurodevelopmental center with classic Rett syndrome (n = 5), autism spectrum disorder (n = 94), epileptic encephalopathy of unknown cause (n = 22), and nonsyndromal mental retardation (n = 23). The prevalence of Rett syndrome among female Chinese younger than 35 years in Hong Kong West is 0.57 (95% confidence interval, 0.15-0.98) per 10 000. Survival is 100.0% at 10 years and 87.5% at 25 years. Three hotspot mutations (R106W, R255X, and R306C) were found in 3 girls with classic Rett syndrome. No hotspot MECP2 mutations were found in the other 3 cohorts. Screening of MECP2 mutations is not worthwhile in Chinese children with pure cognitive, autistic, or unexplained epileptic disorders without other signs of Rett syndrome. In the early stage of developmental arrest before developmental regression, MECP2 screening might be useful for girls with unexplained epileptic encephalopathy before full-blown classic Rett syndrome is evident.
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PMID:Rett syndrome: prevalence among Chinese and a comparison of MECP2 mutations of classic Rett syndrome with other neurodevelopmental disorders. 1817 59

Several lines of evidence indicate a role of mutations in the two X-linked genes neuroligin 3 (NLGN3) and neuroligin 4 (NLGN4X) in the etiology of autistic spectrum disorders. To analyze whether genetic variants in the NLGN3 and NLGN4X genes occurs in patients with autistic disorders on high functioning level, we performed a mutation screen of both genes using SSCP in 107 probands with Asperger syndrome, high-functioning autism and atypical autism. We identified four polymorphisms (rs2290488, rs7049300, rs3747333, rs3747334) and one novel synonymous variant (A558) in the NLGN4X. The polymorphisms rs7049300, rs3747333, and rs3747334 did not cause any amino acid substitutions in the total of the eight detected carriers. A family-based association study for rs2290488 in 101 trios did not reveal association of this polymorphism with autistic disorders on high functioning level. We conclude that there is no evidence for an involvement of NLGN3 and NLGN4X genetic variants with autism spectrum disorder on high functioning level in our study group.
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PMID:No evidence for involvement of genetic variants in the X-linked neuroligin genes NLGN3 and NLGN4X in probands with autism spectrum disorder on high functioning level. 1818 81

Neuroligin 4 (NLGN4) is a member of a cell adhesion protein family that appears to play a role in the maturation and function of neuronal synapses. Mutations in the X-linked NLGN4 gene are a potential cause of autistic spectrum disorders, and mutations have been reported in several patients with autism, Asperger syndrome, and mental retardation. We describe here a family with a wide variation in neuropsychiatric illness associated with a deletion of exons 4, 5, and 6 of NLGN4. The proband is an autistic boy with a motor tic. His brother has Tourette syndrome and attention deficit hyperactivity disorder. Their mother, a carrier, has a learning disorder, anxiety, and depression. This family demonstrates that NLGN4 mutations can be associated with a wide spectrum of neuropsychiatric conditions and that carriers may be affected with milder symptoms.
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PMID:Familial deletion within NLGN4 associated with autism and Tourette syndrome. 1823 Nov 25

Rett Syndrome, an X-linked dominant neurodevelopmental disorder characterized by regression of language and hand use, is primarily caused by mutations in methyl-CpG-binding protein 2 (MECP2). Loss of function mutations in MECP2 are also found in other neurodevelopmental disorders such as autism, Angelman-like syndrome and non-specific mental retardation. Furthermore, duplication of the MECP2 genomic region results in mental retardation with speech and social problems. The common features of human neurodevelopmental disorders caused by the loss or increase of MeCP2 function suggest that even modest alterations of MeCP2 protein levels result in neurodevelopmental problems. To determine whether a small reduction in MeCP2 level has phenotypic consequences, we characterized a conditional mouse allele of Mecp2 that expresses 50% of the wild-type level of MeCP2. Upon careful behavioral analysis, mice that harbor this allele display a spectrum of abnormalities such as learning and motor deficits, decreased anxiety, altered social behavior and nest building, decreased pain recognition and disrupted breathing patterns. These results indicate that precise control of MeCP2 is critical for normal behavior and predict that human neurodevelopmental disorders will result from a subtle reduction in MeCP2 expression.
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PMID:A partial loss of function allele of methyl-CpG-binding protein 2 predicts a human neurodevelopmental syndrome. 1832 64


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