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)

Myotonic dystrophy (DM) is a dominant neuromuscular disorder caused by the expansion of trinucleotide CTG repeats in the 3-untranslated region (3'-UTR) of the MtPK gene. Although DM-associated mental retardation suggests that neuronal functions are disturbed by the expansion mutation, the effect of this alteration in neuronal cells has not been approached. In this study we established stable transfectans of PC12 neuronal cell line expressing the reporter gene CAT alone (empty-vector clone) or fused to the MtPK 3'-UTR with 5, 60, or 90 CTG repeats (CTG5, CTG60, and CTG90 clones, respectively). CTG90 cells exhibited a suppression of NGF-induced neuronal differentiation while empty-vector, CTG5 and CTG60 clones differentiated normally. CTG90 cells displayed normal activation of early differentiation markers, ERK1/2, but the up-regulation of the late marker MAP2 was dramatically reduced. Our neuronal cell system provides the first information of how the mutant MtPK 3'-UTR mRNA affects neuronal functions.
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PMID:Expanded CTG repeats inhibit neuronal differentiation of the PC12 cell line. 1215 Sep 45

The renin-angiotensin system (RAS) is essential for blood pressure control and water-electrolyte balance. Until the discovery of the renin receptor, renin was believed to be mainly a circulating enzyme with a unique function, the cleavage of angiotensinogen. We report a unique mutation in the renin receptor gene (ATP6AP2) present in patients with X-linked mental retardation and epilepsy (OMIM no. 300423), but absent in 1200 control X-chromosomes. A silent mutation (c.321C>T, p.D107D) residing in a putative exonic splicing enhancer site resulted in inefficient inclusion of exon 4 in 50% of renin receptor mRNA, as demonstrated by quantitative RT-PCR. Analysis of membrane associated-receptor molecular forms showed the presence of full-length and truncated proteins in the patient. Functional analysis demonstrated that the mutated receptor could bind renin and increase renin catalytic activity, similar to the wild-type receptor, but resulted in a modest and reproducible impairment of ERK1/2 activation. Thus, our findings confirm the importance of the RAS in cognitive processes and indicate a novel specific role for the renin receptor in cognitive functions and brain development.
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PMID:A unique exonic splice enhancer mutation in a family with X-linked mental retardation and epilepsy points to a novel role of the renin receptor. 1574 49

Mutations in FMR1, which encodes the fragile X mental retardation protein (FMRP), are the cause of fragile X syndrome (FXS), an X-linked mental retardation disorder. Inactivation of the mouse gene Fmr1 confers a number of FXS-like phenotypes including an enhanced susceptibility to epileptogenesis during development. We find that in a FXS mouse model, in which the function of FMRP is suppressed, synaptically released glutamate induced prolonged epileptiform discharges resulting from enhanced group I metabotropic glutamate receptor (mGluR)-mediated responses in hippocampal slices. The induction of the group I mGluR-mediated, prolonged epileptiform discharges was inhibited in preparations that were pretreated with inhibitors of ERK1/2 (extracellular signal-regulated kinase 1/2) phosphorylation or of mRNA translation, and their maintenance was suppressed by group I mGluR antagonists. The results suggest that FMRP plays a key role in the control of signaling at the recurrent glutamatergic synapses in the hippocampus. The absence of this control causes the synaptically activated group I mGluRs to elicit translation-dependent epileptogenic activities.
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PMID:Prolonged epileptiform discharges induced by altered group I metabotropic glutamate receptor-mediated synaptic responses in hippocampal slices of a fragile X mouse model. 1613 62

Cardio-facio-cutaneous (CFC) syndrome is a multiple congenital anomaly/mental retardation syndrome characterized by heart defects, a distinctive facial appearance, ectodermal abnormalities and mental retardation. Clinically, it overlaps with both Noonan syndrome and Costello syndrome, which are caused by mutations in two genes, PTPN11 and HRAS, respectively. Recently, we identified mutations in KRAS and BRAF in 19 of 43 individuals with CFC syndrome, suggesting that dysregulation of the RAS/RAF/MEK/ERK pathway is a molecular basis for CFC syndrome. The purpose of this study was to perform comprehensive mutation analysis in 56 patients with CFC syndrome and to investigate genotype-phenotype correlation. We analyzed KRAS, BRAF, and MAP2K1/2 (MEK1/2) in 13 new CFC patients and identified five BRAF and one MAP2K1 mutations in nine patients. We detected one MAP2K1 mutation in three patients and four new MAP2K2 mutations in four patients out of 24 patients without KRAS or BRAF mutations in the previous study [Niihori et al., 2006]. No mutations were identified in MAPK3/1 (ERK1/2) in 21 patients without any mutations. In total, 35 of 56 (62.5%) patients with CFC syndrome had mutations (3 in KRAS, 24 in BRAF, and 8 in MAP2K1/2). No significant differences in clinical manifestations were found among 3 KRAS-positive patients, 16 BRAF-positive patients, and 6 MAP2K1/2-positive patients. Wrinkled palms and soles, hyperpigmentation and joint hyperextension, which have been commonly reported in Costello syndrome but not in CFC syndrome, were observed in 30-40% of the mutation-positive CFC patients, suggesting a significant clinical overlap between these two syndromes.
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PMID:Molecular and clinical characterization of cardio-facio-cutaneous (CFC) syndrome: overlapping clinical manifestations with Costello syndrome. 1736 77

The (pro)renin receptor [(P)RR] is a single trans-membrane domain receptor that mediates renin and prorenin specific effects. The receptor acts as co-factor for renin and prorenin by increasing their enzymatic activity on the cell-surface and it activates the mitogen activated protein kinases ERK1/2 cascade leading to cell proliferation and to up-regulation of profibrotic genes expression. Studies in genetically modified animals over-expressing (P)RR suggest a direct role for (P)RR cardiovascular and renal pathologies since rats over-expressing (P)RR in vascular smooth-muscle cells develop high blood pressure and those with an ubiquitous over-expression of (P)RR have glomerulosclerosis and proteinuria. A peptide called "handle region peptide" (HRP) mimicking part of the prosegment of prorenin was claimed to block prorenin binding to (P)RR and its activation. The mechanism of action of HRP and its specificity for (P)RR remains very controversial although infusion of this peptide gave spectacular results by preventing diabetic nephropathy in angiotensin II type1a receptor-deficient mice. In contrast to the other components of the renin angiotensin system, (P)RR is necessary to cell survival and proliferation and a mutation of (P)RR is associated with mental retardation and epilepsy, pointing to an essential role of (P)RR in brain development. The (pro)renin receptor is a more complex protein than anticipated and in depth studies of its functions that are likely not restricted to the renin angiotensin system are needed especially in the perspective of the design of a (P)RR blocker.
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PMID:Physiology and pharmacology of the (pro)renin receptor. 1824 93

Developmental thyroid hormone (TH) deficiency leads to mental retardation and neurological deficits in humans. In this study, congenital hypothyroidism was induced in rats by adding 0.05% 6-propyl-2-thiouracil in the drinking water during gestation and suckling period. This treatment induced hyperphosphorylation of neurofilaments, the neuronal intermediate filament (IF) proteins, of heavy, medium and low molecular weight (NF-H, NF-M and NF-L, respectively) without altering the phosphorylation level of astrocyte IF proteins, glial fibrillary acidic protein (GFAP) and vimentin in cerebral cortex of rats. NF-H was hyperphosphorylated on KSP repeats in the carboxy-terminal tail domain. Furthermore, the immunocontent of GFAP and NF subunits was down-regulated, while vimentin was unaltered both in tissue homogenate and in cytoskeletal fraction of hypothyroid animals. Moreover, we verified the immunocontent of astrocyte glutamate/aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1) as well as activation of mitogen-activated protein kinases (MAPKs) in hypothyroid rats. Results showed that hypothyroidism is associated with decreased GLAST and GLT-1 immunocontent. Additionally, we demonstrated increased extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation without altering Jun N-terminal kinase (JNK) and p38(MAPK) phosphorylation. However, total JNK levels were down-regulated. Taken together, these results suggest that the thyroid status could modulate the integrity of neuronal cytoskeleton acting on the endogenous NF-associated phosphorylating system and that such effect could be related to glutamate-induced excitotoxicity, as well as ERK1/2 and JNK modulation. These events could be somehow related to the neurological dysfunction described in hypothyroidism.
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PMID:Congenital hypothyroidism is associated with intermediate filament misregulation, glutamate transporters down-regulation and MAPK activation in developing rat brain. 1884 85

The (pro)renin receptor [(P)RR] plays a pivotal role in the renin-angiotensin system. Experimental models emphasize the role of (P)RR in organ damage associated with hypertension and diabetes. However, a mutation of the (P)RR gene, resulting in frame deletion of exon 4 [Delta4-(P)RR] is associated with X-linked mental retardation (XLMR) and epilepsy pointing to a novel role of (P)RR in brain development and cognitive function. We have studied (P)RR expression in mouse brain, as well as the effect of transfection of Delta4-(P)RR on neuronal differentiation of rat neuroendocrine PC-12 cells induced by nerve growth factor (NGF). In situ hybridization showed a wide distribution of (P)RR, including in key regions involved in the regulation of blood pressure and body fluid homeostasis. In mouse neurons, the receptor is on the plasma membrane and in synaptic vesicles, and stimulation by renin provokes ERK1/2 phosphorylation. In PC-12 cells, (P)RR localized mainly in the Golgi and in endoplasmic reticulum and redistributed to neurite projections during NGF-induced differentiation. In contrast, Delta4-(P)RR remained cytosolic and inhibited NGF-induced neuronal differentiation and ERK1/2 activation. Cotransfection of PC-12 cells with (P)RR and Delta4-(P)RR cDNA resulted in altered localization of (P)RR and inhibited (P)RR redistribution to neurite projections upon NGF stimulation. Furthermore, (P)RR dimerized with itself and with Delta4-(P)RR, suggesting that the XLMR and epilepsy phenotype resulted from a dominant-negative effect of Delta4-(P)RR, which coexists with normal transcript in affected males. In conclusion, our results show that (P)RR is expressed in mouse brain and suggest that the XLMR and epilepsy phenotype might result from a dominant-negative effect of the Delta4-(P)RR protein.
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PMID:A role of the (pro)renin receptor in neuronal cell differentiation. 1949 75

Fragile X syndrome (FXS), a common form of inherited mental retardation, is caused by the lack of fragile X mental retardation protein (FMRP). The animal model of FXS, Fmr1 knockout mice, have deficits in the Morris water maze and trace fear memory tests, showing impairment in hippocampus-dependent learning and memory. However, results for synaptic long-term potentiation (LTP), a key cellular model for learning and memory, remain inconclusive in the hippocampus of Fmr1 knockout mice. Here, we demonstrate that FMRP is required for glycine induced LTP (Gly-LTP) in the CA1 of hippocampus. This form of LTP requires activation of post-synaptic NMDA receptors and metabotropic glutamateric receptors, as well as the subsequent activation of extracellular signal-regulated kinase (ERK) 1/2. However, paired-pulse facilitation was not affected by glycine treatment. Genetic deletion of FMRP interrupted the phosphorylation of ERK1/2, suggesting the possible role of FMRP in the regulation of the activity of ERK1/2. Our study provide strong evidences that FMRP participates in Gly-LTP in the hippocampus by regulating the phosphorylation of ERK1/2, and that improper regulation of these signaling pathways may contribute to the learning and memory deficits observed in FXS.
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PMID:Fragile X mental retardation protein is required for chemically-induced long-term potentiation of the hippocampus in adult mice. 1965 72

The (pro)renin receptor [(P)RR] specifically binds renin and prorenin and mediates their intracellular effects. It acts as co-factor for renin and prorenin by increasing their enzymatic activity on the cell-surface and it activates the mitogen activated protein kinases ERK1/2 (extracellular signal regulated kinase) cascade leading to cell proliferation and to upregulation of profibrotic genes expression. Studies in genetically modified animals over-expressing ubiquitously (P)RR or specifically in smooth-muscle cells suggest a direct role for (P)RR cardiovascular and renal pathologies. A putative (P)RR blocker consisting in part of the prosegment of prorenin gave spectacular results in the prevention of diabetic nephropathy and cardiac fibrosis but its mechanism of action and its specificity for (P)RR remain controversial. Unexpectedly, the total ablation of (P)RR gene is impossible in contrast to the other components of the renin angiotensin system (RAS) and studies in zebra fish and in embryonic stem cells indicate that (P)RR is necessary to cell survival and proliferation. Furthermore, a mutation of (P)RR is associated with mental retardation and epilepsy, pointing to an essential role of (P)RR in brain development. If the role of (P)RR in cardiovascular and renal diseases can be confirmed in (P)RR knockout animals, the benefit of a (P)RR blocker in order to optimize the tissue RAS blockade should really be addressed but not without a good understanding of all its functions and not only those related to the RAS.
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PMID:Twenty years of the (pro)renin receptor. 2040 87

Shank3/PROSAP2 gene mutations are associated with cognitive impairment ranging from mental retardation to autism. Shank3 is a large scaffold postsynaptic density protein implicated in dendritic spines and synapse formation; however, its specific functions have not been clearly demonstrated. We have used RNAi to knockdown Shank3 expression in neuronal cultures and showed that this treatment specifically reduced the synaptic expression of the metabotropic glutamate receptor 5 (mGluR5), but did not affect the expression of other major synaptic proteins. The functional consequence of Shank3 RNAi knockdown was impaired signaling via mGluR5, as shown by reduction in ERK1/2 and CREB phosphorylation induced by stimulation with (S)-3,5-dihydroxyphenylglycine (DHPG) as the agonist of mGluR5 receptors, impaired mGluR5-dependent synaptic plasticity (DHPG-induced long-term depression), and impaired mGluR5-dependent modulation of neural network activity. We also found morphological abnormalities in the structure of synapses (spine number, width, and length) and impaired glutamatergic synaptic transmission, as shown by reduction in the frequency of miniature excitatory postsynaptic currents (mEPSC). Notably, pharmacological augmentation of mGluR5 activity using 3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl)-benzamide as the positive allosteric modulator of these receptors restored mGluR5-dependent signaling (DHPG-induced phosphorylation of ERK1/2) and normalized the frequency of mEPSCs in Shank3-knocked down neurons. These data demonstrate that a deficit in mGluR5-mediated intracellular signaling in Shank3 knockdown neurons can be compensated by 3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl)-benzamide; this raises the possibility that pharmacological augmentation of mGluR5 activity represents a possible new therapeutic approach for patients with Shank3 mutations.
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PMID:Importance of Shank3 protein in regulating metabotropic glutamate receptor 5 (mGluR5) expression and signaling at synapses. 2179 92


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