Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

M6 is a neuronal membrane glycoprotein that may have an important role in neural development. This molecule was initially defined by a monoclonal antibody that affected the survival of cultured cerebellar neurons and the outgrowth of neurites. The nature of the antigen was discovered by expression cDNA cloning using this monoclonal antibody. Two distinct murine M6 cDNAs (designated M6a and M6b) whose deduced amino acid sequences were remarkably similar to that of the myelin proteolipid protein were previously isolated. We have isolated partial human cDNA and genomic clones encoding M6a and M6b and have characterized them by restriction mapping, Southern hybridization with cDNA probes, and sequence analysis. We have localized these genes within the human genome by FISH (fluorescence in situ hybridization). The human M6a gene is located at 4q34, and the M6b gene is located at Xp22.2. A number of human neurological disorders have been mapped to the Xp22 region, including Aicardi syndrome (MIM 304050), Rett syndrome (MIM 312750), X-linked Charcot-Marie-Tooth neuropathy (MIM 302801), and X-linked mental retardation syndromes (MRX1, MIM 309530). This raises the possibility that a defect in the M6b gene is responsible for one of these neurological disorders.
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PMID:Chromosomal mapping of the human M6 genes. 866 Oct 15

Cyclooxygenase or prostaglandin endoperoxide H synthase-2 (PGHS-2) is the first enzyme in the prostanoid biosynthetic pathways and, in brain, it is regulated as an immediate-early gene (IEG). PGHS-2 mRNA and protein are rapidly induced by physiological synaptic activity, and high basal expression in cerebral cortex appears to be maintained by the natural synaptic activity. In contrast to other IEGs, PGHS-2 is a dendritic protein that is enriched in dendritic spines and is, therefore, likely to play a direct role in synaptic physiology. Consistent with a signaling function in mature dendritic spines, PGHS-2 expression is strongly regulated during normal postnatal development in the rat, with peak expression during the third and fourth weeks. Here we use immunocytochemical approaches to compare the developmental expression of PGHS-2 in rat neocortex with that of other well characterized markers of dendritic maturation. PGHS-2 immunoreactivity (ir) follows histogenetic gradients and expression in secondary or more distal dendrites postdates that of even the most delayed dendritic proteins. This developmental pattern parallels the critical period for somatosensory and visual cortex development. Accordingly, PGHS-2-ir may be a useful marker of the final activity-dependent stages of cortical development. Consistent with the potential histochemical utility, we demonstrate that the normal laminar pattern of PGHS-2-ir in human cortex is altered in patients with Rett syndrome, a form of mental retardation with known alterations of dendritic maturation. Further studies of the developmental expression of PGHS-2 in human cortical development may permit analyses of dendritic abnormalities, in syndromes associated with disturbances of activity-dependent development, as well as provide an anatomic basis for understanding the role of prostaglandin signaling in cortical development.
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PMID:Cyclooxygenase-2 expression during rat neocortical development and in Rett syndrome. 907 87

Several X-linked disorders affect females disproportionately or exclusively. These including focal dermal hypoplasia, oral-facial-digital syndrome type I (ref. 3) and epilepsy with bilateral periventricular heterotopias. X-linked dominant inheritance with male lethality is probably responsible for sex-limited expression of these disorders, as affected women have frequent spontaneous abortions and the sex ratio of their live offspring is often skewed. The same inheritance pattern has been proposed for Rett syndrome, Aicardi syndrome and microphthalmia with linear skin defects, but in these sporadic conditions, evidence of male lethality is lacking. We investigated an unusual family with epilepsy and mental retardation limited to females (EFMR, #121250 in ref. 9); this disorder is transmitted both by females and by completely unaffected carrier males. Assignment of the EFMR disease locus (EFMR) to the X chromosome indicates that selective involvement of females in X-linked disease may in some instances result from male sparing rather than male lethality.
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PMID:Epilepsy and mental retardation limited to females: an X-linked dominant disorder with male sparing. 928 83

We present a patient with distinctive clinical manifestations resembling those first described by Pitt and Hopkins in 1978 [Aust Pediatr J 14:182-184] as a separate entity. Cardinal findings in this syndrome are mental retardation, "coarse" face, and an abnormal breathing pattern. The symptoms in this patient are different from those in the Joubert syndrome, Rett syndrome, Rett-like variants, and of a case reported by Leifer et al. [1991: Dysmorph Clin Genet 5:42-47]. The manifestations in our patient and in the case described by Singh [1993: J Paediatric Child Health 29:156-157] seem to confirm the delineation of this syndrome the cause of which remains unknown.
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PMID:Mental retardation, "coarse" face, and hyperbreathing: confirmation of the Pitt-Hopkins syndrome. 947 96

Rett syndrome (RS) is one of the most frequent causes of mental retardation in females. As there are no known biochemical, genetic, or morphological markers, diagnosis is based on clinical phenotype including severe dementia, autism, truncal ataxia/apraxia, loss of purposeful hand movements, breathing abnormalities, stereotypies, seizures, and extrapyramidal signs. Myoclonus, although reported in some series, has never been characterized. We studied 10 RS patients, age 3 to 20 years, and observed myoclonus in 9. Severity of myoclonus did not correlate with that of the other symptoms or with age. Multifocal, arrhythmic, and asynchronous jerks mainly involved distal limbs. Electromyographic bursts lasted 48 +/- 12 msec. Burst-locked electroencephalographic averaging generated a contralateral centroparietal premyoclonus transient preceding the burst by 34 +/- 7.2 msec. Motor evoked potentials showed normal latencies, indicating integrity of the corticospinal pathway. Somatosensory evoked potentials were enlarged. The C-reflex was hyperexcitable and markedly prolonged (62 +/- 4.3 msec), mainly due to increase in cortical relay time (28.4 +/- 4.5 msec). We conclude that RS patients show a distinctive pattern of cortical reflex myoclonus with prolonged intracortical delay of the long-loop reflex.
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PMID:Cortical reflex myoclonus in Rett syndrome. 954 28

Indices of both platelet serotoninergic system and the system of nerve growth factor (NGF) were examined in children with neurofibromatosis (15 patients), polygenic oligophrenia (24 patients) and Rett's syndrome (14 ones). There was an increase of both the level of blood serum autoantibodies (aAB) to NGF and the value of specific binding of 3H-imipramine (Bmax) in platelets of patients with oligophrenia. For this group of patients a significant negative correlation exists between the rate of platelet uptake of serotonin (Vmax value) and the degree of mental retardation (r = -0.425, p < 0.03). Decrease of both Vmax and activity of platelet NGF receptors was revealed in patients with neurofibromatosis. In such patients there was positive correlation between sensitivity of platelet NGF receptors to NGF (during their stimulation by test dose of purified NGF) and the degree of mental retardation (r = 0.697, p < 0.04). In patients with Rett's syndrome a significant increase of activity of platelet NGF receptors to NGF was observed. The conclusion was made on the existence of some general mechanism of intellectual defect development. Autoimmune processes considered to be such mechanism.
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PMID:[The indices of the thrombocyte serotonin system and of the nerve growth factor system in children with hereditary disorders of neuropsychic development]. 957 27

The gene for the gastrin-releasing peptide receptor (GRPR) has been mapped to a candidate region for Rett syndrome (RTT) on the short arm of the X chromosome. The recent report of a translocation that disrupted the gene in an individual with mental retardation and autistic behavior prompted us to examine GRPR as a possible locus for RTT. Genomic polymerase chain reaction amplification of exons followed by single-strand conformation analysis screening in 25 unrelated RTT-affected individuals and by direct sequencing in 12 others has failed to detect any mutation. No gross structural rearrangements were found by Southern analysis of DNA from six unrelated RTT-affected individuals. A high-frequency biallelic polymorphism caused by two single nucleotide substitutions in exon 2 was discovered. The allele frequencies were identical in the RTT population as compared to 100 normal control X chromosomes. This polymorphism will enable future evaluation of the GRPR locus as a candidate for other X-linked mental retardation or neurobehavioral syndromes.
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PMID:Exclusion of the gastrin-releasing peptide receptor (GRPR) locus as a candidate gene for Rett syndrome. 967 11

We determined the diagnostic value of the EEG in young children with Angelman syndrome (AS) and Rett syndrome (RS). EEGs, recorded before 5 years of age, of 10 patients with AS, 10 with RS and 10 with mental retardation of other origin were studied blindly by two examiners for the presence of the following items: (A) 4-6 Hz rhythmic activity of over 200 microV; (B) 2-3 Hz frontal activity of 200-500 microV; (C) posterior spikes; (D) triphasic frontal waves; (E) central and/or centro-temporal spike-wave complexes; and (F) other epileptic discharges. Based on these items the EEGs were scored as AS (A-D); RS (E-F); or other. Examiners never made a mistake between AS and RS. One examiner labeled 6 of 10 AS cases correctly, the other 5; 4 (5) were characterized as 'other.' In RS cases 5 were labeled as 'other' by the first examiner and 3 by the second one. We conclude that EEG patterns of AS and RS are sufficiently different to help differentiate between AS and RS at a young age, which has a bearing on genetic counseling.
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PMID:The diagnostic value of the EEG in Angelman and Rett syndrome at a young age. 968 Jan 52

Formerly thought to be a neurodegenerative disease, Rett syndrome (RS) is a neurodevelopmental arrest of the brain that almost exclusively affects females and occurs in a variety of racial and ethnic groups worldwide. RS begins in late infancy and is characterized by autistic and dementia-like behavior, ataxia, and purposeless hand movements. Its cause and mode of transmission are unknown in over 90% of cases; however, there is strong and convincing evidence that genetic factors play a major role. The reported incidence varies, but in the US, as many as one quarter to one third of female children in mental wards/institutions may be affected. RS has been mistaken for numerous other conditions, including autism, cerebral palsy, and mental retardation, but the clinical picture is unique: No other condition has a period of rapid deterioration followed by apparent stabilization or even improvement in autistic features, eye contact, seizure activity, and hand stereotypies. The diagnosis is supported by deceleration of head growth, evidence of neurologic regression with associated neurologic signs, and purposeless hand stereotypies, with a clinical history of developmental regression. The differential diagnosis often involves ruling out syndromes with similar signs of neurodevelopmental arrest--for example, meningitis or encephalitis; chromosomal disorders such as Angelman's syndrome and Prader-Willi syndrome; metabolic disorders such as ornithine carbamoyltransferase deficiency; disorders of organic acids and amino acids; neurovisceral storage diseases; mitochondrial cytopathy; and Batten disease, or infantile neuronal ceroid lipofuscinosis. Management encompasses a comprehensive medical, therapeutic, educational, and psychosocial approach, best provided through a team in collaboration with the community agencies that serve families and children with special needs.
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PMID:Understanding, Recognizing, and Treating Rett Syndrome. 974 85

The branching of dendrites of pyramidal neurons in premotor frontal, motor and limbic cortex have been identified by us using Golgi technique to be less in Rett Syndrome (RS) brains than in non-Rett control brains. Decreased dendritic branching per se is not pathognomonic of a particular condition and has been reported in numerous disorders associated with mental retardation. This study was designed to test whether the dendritic alterations in Rett Syndrome are the same or different from the alterations present in Down Syndrome (DS), 1 specific form of mental retardation. Sections from Brodmann's areas 6, 4, 20, 43, 28, and 17 of premotor frontal, motor cortex, inferior temporal gyrus, hippocampal formation and the striate cortex from 16 Rett brains, 9 non-Rett brains and 9 Down's brains were prepared for dendrite analysis using the rapid Golgi technique. Drawings of apical and basilar dendrites of pyramidal neurons from 2 cortical layers and Cal were submitted to Sholl analysis. The analyses of Rett brains were compared with the analyses of the Trisomy 21 brains using the repeated measures analysis of covariance, with age as a covariate. The studies demonstrate in our sample that basal dendrites of layer III and V of frontal, layer IV of subiculum, and layer V of motor cortex and apical dendrites of layer III of frontal cortex have a significantly reduced dendritic arborization in RS compared with Trisomy 21. This study suggests that the cortical distribution of the dendritic alterations is specific for Rett Syndrome, and that the premotor frontal, motor and subicular cortex are preferentially involved in the, as yet, undefined process which affects brain growth and function in RS.
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PMID:Decreased dendritic branching in frontal, motor and limbic cortex in Rett syndrome compared with trisomy 21. 982 37


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