Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
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Rett syndrome is caused by mutations in MECP2 and characterized by arrested postnatal neurodevelopment. MECP2 is ubiquitously expressed, but its protein product, methyl-CpG-binding protein 2 (MeCP2), is highly expressed in a subpopulation of cells in the adult brain. Automated quantitation of MeCP2 expression on a human developmental tissue microarray was performed by laser scanning cytometry. A significant correlation between age and MeCP2 level, population heterogeneity, and percentage of MeCP2 high-expressing cells was specifically observed in cerebral but not renal samples. In contrast, an inverse correlation between use of the long 3' UTR of MECP2 and age was observed, suggesting that an acquired switch in polyadenylation is responsible for the elevated MeCP2. Acquired elevated MeCP2 expression in neurons beginning in infancy and progressing through childhood may explain the delayed onset and developmental arrest of Rett syndrome
J Mol Med (Berl) 2003 Jan
PMID:Elevated methyl-CpG-binding protein 2 expression is acquired during postnatal human brain development and is correlated with alternative polyadenylation. 1254 50

Rett syndrome is a neurodevelopmental disorder that affects females almost exclusively, and in which eight common point mutations on the X-linked MeCP2 gene are knows to cause over 70% of mutation-positive cases. We explored the use of a novel platform to detect the eight common mutations in Rett syndrome patients to expedite and simplify the process of identification of known genotypes. The Nanogen workstation consists of a two-color assay based on electric hybridization and thermal discrimination, all performed on an electronically active NanoChip. This genotyping platform was tested on 362 samples of a pre-determined genotype, which had been previously identified by a combination of DHPLC (denaturing high performance liquid chromatography) and direct sequencing. This genotyping technique proved to be rapid, facile, and displayed a specificity of 100% with 3% ambiguity. In addition, we present consecutive testing of seven mutations on a single pad of the NanoChip. This was accomplished by tagging down two amplimers together and serially hybridizing for seven different loci, allowing us to genotype samples for seven of the eight common Rett mutations on a single pad. This novel method displayed the same level of specificity and accuracy as the single amplimer reactions, and proved to be faster and more economical.
J Mol Diagn 2003 May
PMID:Rapid genotyping of common MeCP2 mutations with an electronic DNA microchip using serial differential hybridization. 1270 77

Rett syndrome, a neurodevelopmental disorder hypothesized to be due to defective neuronal maturation, is a result of mutations in the mecp2 gene encoding the transcriptional repressor methyl-CpG binding protein (MeCP2). We utilized the olfactory system, which displays postnatal neurogenesis, as a model to investigate MeCP2 expression during development and after injury. MeCP2 expression increased postnatally, localizing to mature olfactory receptor neurons (ORNs) and sustentacular supporting cells. The timing of MeCP2 expression was defined by using detergent ablation (to remove the ORNs) and unilateral olfactory bulbectomy (to remove the ORN target), both of which increase neurogenesis. MeCP2 expression in the ORNs reached prelesioning levels as cells matured after ablation, whereas expression was not completely restored after bulbectomy, in which functional synaptogenesis cannot occur. Thus, MeCP2 expression correlates with the maturational state of ORNs, and precedes synaptogenesis. Identifying the time window of MeCP2 expression should help further clarify the biological defects in Rett syndrome.
Mol Cell Neurosci 2003 Apr
PMID:Expression of MeCP2 in olfactory receptor neurons is developmentally regulated and occurs before synaptogenesis. 1272 40

Rett syndrome (RTT) is a severe neurodevelopmental disorder affecting almost exclusively girls. It is currently considered a monogenic X-linked dominant disorder due to mutations in MECP2 gene, encoding the methyl-CpG binding protein 2. A few RTT male cases, resulting from mosaicism for MECP2 mutations, have been reported. Male germline MECP2 mutations cause either severe encephalopathy with death at birth (usually in brothers of classical RTT females) or X-linked recessive mental retardation (XLMR). To date the wide phenotypic heterogeneity associated with MECP2 mutations in females (from classical RTT to healthy carriers) has been explained by differences in X chromosome inactivation. However, conflicting results have been obtained in different studies, with both random and highly skewed X-inactivation reported in healthy carrier females. Consequently it is possible that mechanisms other than X-inactivation play a role in the expressivity of MECP2 mutations. To explain the phenotypic heterogeneity associated with MECP2 mutations we propose a digenic model in which the presence of a "mutated" allele in a second gene, leading to a less functional protein, determines the clinical severity of the MECP2 mutation. The model is supported by the identification of the same mutation in XLMR and RTT cases. The carrier mothers of XLMR families are clinically asymptomatic and present balanced X chromosome inactivation. Therefore the same mutation arising in different genetic backgrounds can cause XLMR in males, remain silent in the carrier females and cause classic RTT in females. MECP2 mutations account for approximately 70-80% of classic RTT cases. MECP2 negative cases might result from mutations in noncoding regions of MECP2 gene. Alternatively, these cases might be due to mutations in other genes (locus heterogeneity). This hypothesis is supported by the identification of several chromosomal rearrangements in MECP2 negative patients with RTT and RTT-like phenotypes. MeCP2 is considered a general transcriptional repressor. However, conditional mouse mutants with selective loss of Mecp2 in the brain develop clinical manifestations similar to RTT, indicating that MECP2 is exclusively required for central nervous system function. The involvement of MeCP2 in methylation-specific transcriptional repression suggests that MECP2 related disorders result from dysregulated gene expression. Studies on gene expression have been performed in mouse and human brains. A relatively small number of gene expression changes were identified. It is possible that MeCP2 causes dysregulation of a very small subset of genes that are not detected with this method of analysis, or that very subtle changes in many genes cause the neuronal phenotype.
J Mol Med (Berl) 2003 Jun
PMID:Rett syndrome: the complex nature of a monogenic disease. 1275 Aug 21

Methylation of cytosine in human DNA has been studied for over 60 years, but has only recently been confirmed as an important player in human disease. Rett syndrome is a neurological disorder caused by mutations in the MeCP2 protein, which has been shown to bind methylated DNA and repress transcription. This review will focus on experiments addressing the basic properties of MeCP2 and on mouse models of Rett syndrome that are starting to yield insights into this condition.
Hum Mol Genet 2003 Oct 15
PMID:DNA methylation and Rett syndrome. 1292 86

MeCP2 is a DNA binding protein that represses transcription of methylated genes in vitro, but the endogenous function of MeCP2 in vivo is unclear. Here, we demonstrate that in Xenopus laevis embryos MeCP2 is a partner of the SMRT corepressor complex that regulates the expression of a neuronal repressor xHairy2a in differentiating neuroectoderm. The MeCP2/SMRT complex is bound to the promoter of the silenced xHairy2a gene and is displaced upon activation by the Notch intracellular domain (NICD). A truncated form of MeCP2 (R168X) found in patients with Rett syndrome cannot interact with the SMRT complex or fully activate xHairy2a during primary neurogenesis. This disruption of MeCP2 activity results in abnormal patterning of primary neurons during neuronal differentiation. Our results support a model whereby the dynamic association of MeCP2 with methylated DNA and the SMRT complex regulates a gene involved in cell fate decisions during primary neurogenesis in Xenopus.
Mol Cell 2003 Aug
PMID:A mutant form of MeCP2 protein associated with human Rett syndrome cannot be displaced from methylated DNA by notch in Xenopus embryos. 1453 82

Rett syndrome is a dominant neurological disorder caused by loss-of-function mutations of methyl-CpG-binding protein 2 (MeCP2). MeCP2 is an abundant chromatin-associated protein that contains two well characterized domains. Through an N-terminal domain it recognizes methyl-CpGs and binds to nonmethylated DNA. A domain in the middle of the protein can act as a transcriptional repressor in transient transfection studies. The C-terminal region of the protein is equally essential for the function of MeCP2, as documented by recurrently found frameshift mutations. However, little is known about its functional role. Here we mapped a domain within MeCP2 capable of binding specifically to Group II WW domains of splicing factors formin-binding protein (FBP) 11 and HYPC. Binding was assessed by glutathione S-transferase pull-down assays and coimmunoprecipitation assays. The Group II WW domain binding region was localized from residue 325 to the C-terminus, with the interacting proline-rich sequence at its center. We then used comparison with genotype-phenotype studies in Rett syndrome patients to evaluate the relevance of Group II WW domain interactions of MeCP2 for pathogenesis. Truncation of the WW domain binding region by 48 C-terminal amino acids (to residue 438), causing Rett syndrome, resulted in reduced or loss of WW domain binding activity. Truncation to residue 400, representing a large group of frameshift mutations accounting for approx. 10% of Rett syndrome cases, abolished WW domain binding activity completely. On the other hand, two benign missense mutations did not affect binding. Furthermore, a short C-terminal truncation and an internal deletion, both causing mild to moderate mental retardation in males, were associated with weak or loss of WW domain binding activity.
J Mol Med (Berl) 2004 Feb
PMID:A WW domain binding region in methyl-CpG-binding protein MeCP2: impact on Rett syndrome. 1461 41

Rett syndrome (RTT) is a neurodevelopmental disorder caused by mutations in MECP2, encoding methyl-CpG-binding protein 2 (MeCP2). Although MECP2 is ubiquitously transcribed, MeCP2 expression is developmentally regulated and heterogeneous in neuronal subpopulations, defined as MeCP2(lo) and MeCP2(hi). To test the hypothesis that pathways affecting MeCP2 expression changes may be defective in RTT, autism and other neurodevelopmental disorders without MECP2 mutations, a high-throughput quantitation of MeCP2 expression was performed on a tissue microarray containing frontal cortex samples from 28 different patients with neurodevelopmental disorders and age-matched controls. Combined quantitative analyses of MeCP2 protein and alternatively polyadenylated transcript levels were performed by laser scanning cytometry and tested for significant differences from age-matched controls. Normal cerebral samples showed an increase in total MeCP2 expression and the percentage of MeCP2(hi) cells with age that could be explained by increased MECP2 transcription within the MeCP2(hi) population. A significant decrease in the relative usage of the long transcript in the MeCP2(lo) population was observed in postnatal compared to fetal brain, but alternate polyadenylation did not correlate with MeCP2 expression changes at the single cell level. Brain samples from several related neurodevelopmental disorders, including autism, pervasive developmental disorder, Prader-Willi and Angelman syndromes showed significant differences in MeCP2 expression from age-matched controls by apparently different transcriptional and post-transcriptional mechanisms. These results suggest that multiple pathways regulate the complex developmental expression of MeCP2 and are defective in autism-spectrum disorders in addition to RTT.
Hum Mol Genet 2004 Mar 15
PMID:Multiple pathways regulate MeCP2 expression in normal brain development and exhibit defects in autism-spectrum disorders. 1473 26

Rett syndrome (RTT) is an X-linked neurodevelopmental disorder caused by mutations in MECP2, encoding methyl-CpG-binding protein 2 (MeCP2). The onset of symptoms in RTT is delayed until 6-18 months and 4-6 months in the Mecp2(-/+) mouse model, corresponding to a dynamic and gradual accumulation of MeCP2 expression in individual neurons of the postnatal brain. Because of X chromosome inactivation (XCI), cells within RTT females are mosaic for expression of the heterozygous MECP2 mutation. Using the targeted Mecp2 mouse model, we investigated the effect of Mecp2 mutation on XCI and developmental MeCP2 expression in wild-type (wt)-expressing neurons by quantitative laser scanning cytometry. Mecp2(-/+) female mice exhibited uniform regional distribution of Mecp2 mutant-expressing cells in brain, but unbalanced XCI in the population, favoring expression of the Mecp2 wt allele. Interestingly, MeCP2 expression in Mecp2 wt-expressing cells from Mecp2(-/+) mice was significantly lower than those from Mecp2(+/+) age-matched controls. The negative effect of Mecp2 mutation on wt Mecp2 expression correlated with the percentage of Mecp2 mutant-expressing cells in the cortex. Similar results were observed in two RTT females with identical MECP2 mutations but different XCI ratios. These results demonstrate that Mecp2-mutant neurons affect the development of surrounding neurons in a non-cell-autonomous manner and suggest that environmental influences affect the level of MeCP2 expression in wt neurons. These results help in explaining the role of XCI in the pathogenesis of RTT and have important implications in designing therapies for female RTT patients.
Hum Mol Genet 2004 Jun 15
PMID:X-Chromosome inactivation ratios affect wild-type MeCP2 expression within mosaic Rett syndrome and Mecp2-/+ mouse brain. 1511 65

Several thousand EST sequences were recently made available in the EMBL sequence database from the rainbow trout Oncorhynchus mykiss. BLAST based searches were utilised to identify sequences resembling mammalian CC chemokines within these ESTs. Fifteen new and unique CC chemokine-like sequences were identified for trout, bringing the total of known CC chemokine sequences in trout to 18 when including those already published. Some of these trout chemokines appeared highly related (in pairs) suggesting recent duplication events or tight evolutionary constraints. Phylogenetically, the trout chemokine sequences grouped with both inducible and constitutive mammalian CC chemokine subtypes, suggesting early divergence of these functional groups. Expression analyses on gill and head kidney show constitutive expression of many of these trout CC chemokines in these lymphoid-rich tissues. However, induction of some of the chemokines structurally related to 'inducible' CC chemokines was observed in a trout macrophage-like cell line (RTS-11) in response to stimulation with recombinant TNFalpha.
Mol Immunol 2004 Jul
PMID:Trout CC chemokines: comparison of their sequences and expression patterns. 1523 59


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