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)

Mutations in the gene coding for methyl-CpG-binding protein 2 (MECP2) cause Rett syndrome (RTT) and have also been reported in a number of X-linked mental retardation syndromes. Furthermore, putative mutations recently have been described in a few autistic patients and a boy with language disorder and schizophrenia. In this study, DNA samples from individuals with schizophrenia and other psychiatric diseases were scanned in order to explore whether the phenotypic spectrum of mutations in the MECP2 gene can extend beyond the traditional diagnoses of RTT in females and severe neonatal encephalopathy in males. The coding regions, adjacent splicing junctions, and highly conserved segments of the 3'-untranslated region (3'-UTR) were examined in 214 patients, including 106 with schizophrenia, 24 with autism, and 84 patients with other psychiatric diseases by detection of virtually all mutations-single strand conformation polymorphism (SSCP) (DOVAM-S). To our knowledge, this is the first analysis of variants in conserved regions of the 3'-UTR of this gene. A total of 5.2 kb per haploid gene was analyzed (1.5 Mb for 214 patients). A higher frequency of missense and 3'-UTR variants was found in autism. One missense and two 3'-UTR variants were found in 24 patients with autism versus one patient with a missense change in 144 ethnically similar individuals without autism (P = 0.009). These mutations suggest that a possible association between MECP2 mutations and autism may warrant further study.
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PMID:MECP2 structural and 3'-UTR variants in schizophrenia, autism and other psychiatric diseases: a possible association with autism. 1521 31

Rett syndrome (RTT) is a severe neurodevelopmental disorder with features of autism that results from mutation of the gene encoding the transcriptional repressor methyl-CpG binding protein (MECP2). The consequences of loss of a transcription factor may be complex, affecting the expression of many proteins, thus limiting understanding of this class of diseases and impeding therapeutic strategies. This is true for RTT. Neither the cell biological mechanism(s) nor the developmental stage affected by MECP2 deficiency is known. In vivo analysis of the olfactory system demonstrates that Mecp2 deficiency leads to a transient delay in the terminal differentiation of olfactory neurons. This delay in maturation disrupts axonal targeting in the olfactory bulb, resulting in abnormal axonal projections, subglomerular disorganization, and a persistent reduction in glomerular size. These results indicate a critical cell biological function for Mecp2 in mediating the final stages of neuronal development.
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PMID:The transcriptional repressor Mecp2 regulates terminal neuronal differentiation. 1534 42

The occurrence of developmental regression in autism is one of the more puzzling features of this disorder. Although several studies have documented the validity of parental reports of regression using home videos, accumulating data suggest that most children who demonstrate regression also demonstrated previous, subtle, developmental differences. Counter to clinical intuition, the earlier development of social, language, and attachment behaviors followed by regression does not seem to support later recovery of skills or better developmental outcomes compared to children who never had speech or typical social responsivity. In fact, this regressive group may have somewhat greater developmental impairment than the nonregressive group, though the two groups do not appear to present different behavioral phenotypes. Although autism is not the only condition in which regression occurs, it appears to be the most frequent condition. Other disorders that demonstrate an early regression with no known etiology include total blindness from birth and childhood disintegrative disorder, both of which demonstrate behavioral relations to autism. In addition, two biological conditions with known etiologies also involve regression with some behaviors resembling autism behavioral phenotype: Rett syndrome (a genetic disorder; see Glaze, this issue) and Landau-Kleffner syndrome (see McVicar and Shinnar, this issue), which involves a seizure disorder.
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PMID:Developmental regression in autism spectrum disorders. 1536 72

Rett syndrome (RTT) is a neurodevelopmental disorder occurring almost exclusively in females. Regression is a defining feature of RTT. During the regression stage, RTT girls display many autistic features, such as loss of communication and social skills, poor eye contact, and lack of interest, and initially may be given the diagnosis of autism. The discovery of the genetic cause of RTT, mutations in the MECP2 gene, a transcriptional repressor, has promoted the early diagnosis of RTT and development of mouse models. The phenotype of one mouse model includes features such as regression and abnormal behavioral and social interactions. The timing of the period of regression in RTT--during ages 1 to 2 years--parallels the period of intense synaptic development. The effects of the MECP2 mutation also increases concomitantly with peak synaptogenesis. Neuropathological findings in Rett include the selective reduction of dendritric spines in the pyramidal cells of RTT brains; this feature has also been reported in autism. Studies have observed that MECP influences the expression of brain-derived neurotrophic factor and thus may influence synaptic plasticity. Abnormalities in synapse maintenance and modulation may contribute to regression in RTT and autism. Studies of the clinical aspects of the regression period and of the mouse model may be useful in understanding the pathophysiology of RTT and other neurodevelopmental disorders such as autism. A recent study observed abnormal expression of MeCP2 in RTT and other neurodevelopmental disorders such as autism. Although the genetic background and certain clinical features differ in RTT and autism, a similar mechanism involving MeCP2 regulation and expression may contribute to regression.
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PMID:Rett syndrome: of girls and mice--lessons for regression in autism. 1536 75

Mutations in the methyl-CpG-binding protein 2 (MECP2) gene are known to underlie Rett' syndrome, the most common cause of mental retardation (MR) in girls. Since the original report, phenotypes resulting from MECP2 mutations have been shown to extend, for example, to several Rett variants, autism, atypical Angelman syndrome, and nonspecific MR. It was earlier proposed that MECP2 mutations might account for approximately 2% of the male cases with nonspecific MR. Thereby, the frequency of MECP2 mutations in the mentally retarded population would be comparable to that of Fragile-X syndrome. The aim of this study was to analyze well-characterized cases with MR and to clarify the role of the MECP2 gene in the etiology of MR and atypical Angelman syndrome. The coding sequence of the MECP2 gene was analyzed in a sample of 118 patients (103 males, 15 females) by direct sequencing. Two coding sequence variants, 602C > T (A201V) and 1189G > A (E397K), were identified. In addition, we identified four variants in the intronic or 3'UTR regions. None of these variants is likely to be causal. We conclude that the evidence across all the mutation screening studies implies that MECP2 mutations do not represent a major cause of nonspecific MR.
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PMID:MECP2 mutation analysis in patients with mental retardation. 1557 81

Autism is a common neurodevelopmental disorder of complex genetic etiology. Rett syndrome, an X-linked dominant disorder caused by MECP2 mutations, and Angelman syndrome, an imprinted disorder caused by maternal 15q11-q13 or UBE3A deficiency, have phenotypic and genetic overlap with autism. MECP2 encodes methyl-CpG-binding protein 2 that acts as a transcriptional repressor for methylated gene constructs but is surprisingly not required for maintaining imprinted gene expression. Here, we test the hypothesis that MECP2 deficiency may affect the level of expression of UBE3A and neighboring autism candidate gene GABRB3 without necessarily affecting imprinted expression. Multiple quantitative methods were used including automated quantitation of immunofluorescence and in situ hybridization by laser scanning cytometry on tissue microarrays, immunoblot and TaqMan PCR. The results demonstrated significant defects in UBE3A/E6AP expression in two different Mecp2 deficient mouse strains and human Rett, Angelman and autism brains compared with controls. Although no difference was observed in the allelic expression of several imprinted transcripts in Mecp2-null brain, Ube3a sense expression was significantly reduced, consistent with the decrease in protein. A non-imprinted gene from 15q11-q13, GABRB3, encoding the beta3 subunit of the GABAA receptor, also showed significantly reduced expression in multiple Rett, Angelman and autism brain samples, and Mecp2 deficient mice by quantitative immunoblot. These results suggest an overlapping pathway of gene dysregulation within 15q11-q13 in Rett, Angelman and autism and implicate MeCP2 in the regulation of UBE3A and GABRB3 expressions in the postnatal mammalian brain.
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PMID:Epigenetic overlap in autism-spectrum neurodevelopmental disorders: MECP2 deficiency causes reduced expression of UBE3A and GABRB3. 1561 69

Rett syndrome (RS), a neurological developmental disorder, is one of the commonest causes of cognitive impairment in girls and women. These patients are often initially misdiagnosed as idiopathic mental retardation, cerebral palsy, or autism. Despite several reports from the West, there are very few reports from the Indian population. We present four female children with RS and emphasize the importance of early diagnosis.
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PMID:Recent experience with Rett syndrome at a tertiary care center. 1562 43

Rett syndrome (RTT), caused by mutations in MECP2 (encoding methyl CpG binding protein 2), and Angelman syndrome (AS), caused by maternal deficiency of chromosome 15q11-13, are autism-spectrum neurodevelopmental disorders. MeCP2 is a transcriptional repressor of methylated genes, but MECP2 mutation does not directly affect the imprinted expression of genes within 15q11-13. We tested a potential role for MeCP2 in the homologous pairing of imprinted 15q11-13 alleles in human brain tissue and differentiated neurons by fluorescence in situ hybridization (FISH). FISH analysis of control cerebral samples demonstrated a significant increase in homologous pairing specific to chromosome 15 from infant to juvenile brain samples. Significant and specific deficiencies in the percentage of paired chromosome 15 alleles were observed in RTT, AS and autism brain samples when compared with normal controls. SH-SY5Y neuroblastoma cells also showed a significant and specific increase in the percentage of chromosome 15q11-13 paired alleles following induced differentiation in vitro. Transfection with a methylated oligonucleotide decoy specifically blocked binding of MeCP2 to the SNURF/SNRPN promoter within 15q11-13 and significantly lowered the percentage of paired 15q11-13 alleles in SH-SY5Y cells. These combined results suggest a role for MeCP2 in chromosome organization in the developing brain and provide a potential mechanistic association between several related neurodevelopmental disorders.
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PMID:Homologous pairing of 15q11-13 imprinted domains in brain is developmentally regulated but deficient in Rett and autism samples. 1568 52

Cognitive development is determined by both genetics and environment. One point of convergence of these two influences is the neural activity-dependent regulation of programs of gene expression that specify neuronal fate and function. Human genetic studies have linked several transcriptional regulators to neurodevelopmental disorders including mental retardation and autism spectrum disorders. Recent reports on two such factors, CREB-binding protein and methyl-CpG-binding protein 2, have begun to reveal how epigenetics and neuronal activity act to modulate the program of gene expression required for synaptic development and function.
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PMID:Transcriptional control of cognitive development. 1572 40

Autism is a neurodevelopmental disorder of genetic origins, with a heritability of about 90%. Autistic disorder is classed within the broad domain of pervasive developmental disorders (PDD) that also includes Rett syndrome, childhood disintegrative disorder, Asperger syndrome, and PDD not otherwise specified (PDD-NOS). Prevalence estimates suggest a rate of 0.1-0.2% for autism and 0.6% for the range of PDD disorders. There is considerable phenotypic heterogeneity within this class of disorders as well as continued debate regarding their clinical boundaries. Autism is the prototypical PDD, and is characterized by impairments in three core domains: social interaction, language development, and patterns of behavior (restricted and stereotyped). Clinical pattern and severity of impairment vary along these dimensions, and the level of cognitive functioning of individuals with autism spans the entire range, from profound mental retardation to superior intellect. There is no single biological or clinical marker for autism, nor is it expected that a single gene is responsible for its expression; as many as 15+ genes may be involved. However, environmental influences are also important, as concordance in monozygotic twins is less than 100% and the phenotypic expression of the disorder varies widely, even within monozygotic twins. Multiple susceptibility factors are being explored using varied methodologies, including genome-wide linkage studies, and family- and case-control candidate gene association studies. This paper reviews what is currently known about the genetic and environmental risk factors, neuropathology, and psychopharmacology of autism. Discussion of genetic factors focuses on the findings from linkage and association studies, the results of which have implicated the involvement of nearly every chromosome in the human genome. However, the most consistently replicated linkage findings have been on chromosome 7q, 2q, and 15q. The positive associations from candidate gene studies are largely unreplicated, with the possible exceptions of the GABRB3 and serotonin transporter genes. No single region of the brain or pathophysiological mechanism has yet been identified as being associated with autism. Postmortem findings, animal models, and neuroimaging studies have focused on the cerebellum, frontal cortex, hippocampus, and especially the amygdala. The cerebello-thalamo-cortical circuit may also be influential in autism. There is evidence that overall brain size is increased in some individuals with autism. Presently there are no drugs that produce major improvements in the core social or pragmatic language deficits in autism, although several have limited effects on associated behavioral features. The application of new techniques in autism research is being proposed, including the investigation of abnormal regulation of gene expression, proteomics, and the use of MRI and postmortem analysis of the brain.
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PMID:What is known about autism: genes, brain, and behavior. 1581 71


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