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)

Tuberous sclerosis (TSC) is an autosomal dominant trait characterized by the widespread development of benign tumours classified as hamartoma, and is often associated with seizures and mental retardation. The patchy distribution and focal nature of the growths suggests that they might result from inactivation of a tumour suppressor gene by a two-hit process. Over the last 2 years, studies designed to investigate both germline and somatic TSC mutations have lent support to this hypothesis. Analysis of TSC-associated hamartomas has shown loss of heterozygosity for the regions of chromosomes 9 and 16 known to harbour TSC genes, consistent with the occurrence of somatic 'second-hit' mutations. Parallel investigations using pulse field gel electrophoresis have identified constitutional deletions representing 'first-hit' mutations at 16p13.3, leading to the rapid identification of one of the causative genes, TSC2. Intriguingly, the TSC2 product, tuberin, has an area of sequence homology with the GTPase activating protein rap1GAP, suggesting a possible mechanism for its role in regulating cellular growth.
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PMID:The molecular genetics of tuberous sclerosis. 784 41

Tuberous sclerosis (TS) is an autosomal dominant disorder in which affected individuals manifest mental retardation, seizures, and a variety of benign and malignant tumors. The TSC2 tumor suppressor gene was recently identified by positional cloning and its protein product, tuberin, shown to represent one member of the rap GTPase activating protein (rapGAP) family. In order to determine the contribution of tuberin to the development of mental retardation and seizures in patients with TS, we examined the expression of tuberin in adult and developing nervous system tissues. Since tuberin is the second rapGAP found in the nervous system, the expression of tuberin was compared to the expression of rapGAP, rap1, and rap2. In this study, we demonstrate that tuberin is expressed at greatest levels in the spinal cord and cerebellum as opposed to rapGAP, which is not enriched in these tissues. Tuberin expression in the adult CNS is restricted to the olfactory bulb, several CNS neuronal populations, brainstem nuclei, cerebellar Purkinje cells, and motor neurons in the ventral spinal cord. In contrast, rapGAP is expressed in many different cell types in the adult CNS, but not in cerebellar Purkinje cells or motor neurons in the ventral spinal cord. However, there is significant expression of rapGAP in astrocytes. The restricted distribution of tuberin expression relative to rap1 and rapGAP suggests that tuberin may be the primary rap1 regulator in a subpopulation of CNS neurons.
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PMID:Expression of the tuberous sclerosis 2 gene product, tuberin, in adult and developing nervous system tissues. 917 18

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by seizures, mental retardation, and tumors of skin, brain, heart, and kidney. In this study, we focused on two of the most frequent tumors in TSC patients, renal angiomyolipomas and subependymal giant cell astrocytomas (SEGAs). Two questions were addressed. First, is loss of tuberin, the product of the TSC2 gene, seen in both renal and central nervous system tumors from TSC patients? Second, when loss of tuberin occurs, does it affect each of the cell types seen in these tumors? We used a loss of heterozygosity approach to identify tumors from TSC2 patients. We found loss of tuberin immunostaining in the spindle and epithelioid cells but not in the giant cells of six TSC2 SEGAs. We also found loss of tuberin immunostaining in all three cell types (smooth muscle, fat, and vessels) of six TSC2 angiomyolipomas. Chromosome 16p13 loss of heterozygosity occurred in both spindle and epithelioid cells of a SEGA and in smooth muscle and fat but not the vessels of two angiomyolipomas. These results support a two-hit tumor suppressor model for the pathogenesis of SEGAs and angiomyolipomas. The vascular elements of angiomyolipomas and the giant cells of SEGAs may be reactive rather than neoplastic.
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PMID:Loss of tuberin in both subependymal giant cell astrocytomas and angiomyolipomas supports a two-hit model for the pathogenesis of tuberous sclerosis tumors. 940 14

Tuberous sclerosis (TSC) is an autosomal dominant disorder caused by a mutation in either the TSC1 or TSC2 tumour suppressor gene. The disease is characterized by a broad phenotypic spectrum that can include seizures, mental retardation, renal dysfunction and dermatological abnormalities. TSC2 encodes tuberin, a putative GTPase activating protein for rap1 and rab5. The TSC1 gene was recently identified and codes for hamartin, a novel protein with no significant homology to tuberin or any other known vertebrate protein. Here, we show that hamartin and tuberin associate physically in vivo and that the interaction is mediated by predicted coiled-coil domains. Our data suggest that hamartin and tuberin function in the same complex rather than in separate pathways.
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PMID:Interaction between hamartin and tuberin, the TSC1 and TSC2 gene products. 958 Jun 71

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by seizures, mental retardation, and hamartomatous tumors in multiple organs, including subependymal giant cell astrocytomas, cardiac rhabdomyomas, and renal angiomyolipomas. Mutations in two genes are associated with TSC: TSC1, which was cloned in 1997, and TSC2, which was cloned in 1993. We report here the expression of hamartin, the product of the TSC1 gene, in normal human tissues and in renal angiomyolipomas from TSC1- and TSC2-linked patients. By Western blot analysis, hamartin is strongly expressed in brain, kidney, and heart, all of which are frequently affected in TSC. By immunohistochemical analysis, the expression pattern of hamartin in normal human tissues was almost identical to that of tuberin, the product of the TSC2 gene. This is consistent with the recent finding that tuberin and hamartin interact and with the clinical similarity between TSC1- and TSC2-linked disease. Strong hamartin expression was seen in cortical neurons, renal tubular epithelial cells, pancreatic islet cells, bronchial epithelial cells, and pulmonary macrophages. Hamartin was also expressed in endocrine tissues, including islet cells of the pancreas, follicular cells of the thyroid, and the zona reticularis of the adrenal cortex. In eight angiomyolipomas from a TSC1-linked patient, no hamartin expression was detected, whereas tuberin, the product of the TSC2 gene, was expressed. In 19 angiomyolipomas from a TSC2-linked patient, in whose angiomyolipomas loss of tuberin expression had previously been shown, hamartin expression was present. These data suggest that tuberin and hamartin immunoreactivity can distinguish tumors with underlying TSC1 mutations from those with TSC2 mutations. This differentiation might have diagnostic implications.
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PMID:The expression of hamartin, the product of the TSC1 gene, in normal human tissues and in TSC1- and TSC2-linked angiomyolipomas. 1034 94

Tuberous sclerosis (TSC) is an autosomal dominant disorder characterized by a broad phenotypic spectrum that includes seizures, mental retardation, renal dysfunction and dermatological abnormalities. Mutations to either the TSC1 or TSC2 gene are responsible for the disease. The TSC1 gene encodes hamartin, a 130-kDa protein without significant homology to other known mammalian proteins. Analysis of the amino acid sequence of tuberin, the 200-kDa product of the TSC2 gene, identified a region with limited homology to GTPase-activating proteins. Previously, we demonstrated direct binding between tuberin and hamartin. Here we investigate this interaction in more detail. We show that the complex is predominantly cytosolic and may contain additional, as yet uncharacterized components alongside tuberin and hamartin. Furthermore, because oligomerization of the hamartin carboxyl-terminal coiled coil domain was inhibited by the presence of tuberin, we propose that tuberin acts as a chaperone, preventing hamartin self-aggregation.
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PMID:Characterization of the cytosolic tuberin-hamartin complex. Tuberin is a cytosolic chaperone for hamartin. 1058 43

Tuberous sclerosis complex (TSC) is a common genetic disorder in which affected individuals can develop mental retardation, developmental brain defects, and seizures. Two genetic loci are responsible for TSC: TSC1 on chromosome 9q and TSC2 on chromosome 16p. Here, we report our analysis of TSC1 (hamartin) and TSC2 (tuberin) protein expression in the central nervous system (CNS). Both tuberin and hamartin are expressed in neurons and astrocytes where they physically interact. In the mouse cerebellum in vivo, tuberin predominantly localizes to the perinuclear region of the Purkinje cell, whereas hamartin is distributed along neuronal or astrocytic processes. In contrast, both hamartin and tuberin demonstrate similar neuronal expression patterns in pure neuronal cultures in vitro. Additionally, hamartin is highly expressed in astrocytes in mixed neuron-glia cultures in vitro, suggesting that hamartin may be important for astrocyte growth control. Unlike tuberin, loss of hamartin expression was not observed in sporadic astrocytomas. These results suggest that tuberin and hamartin may differentially contribute to the CNS pathology in TSC.
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PMID:Expression of the tuberous sclerosis complex gene products, hamartin and tuberin, in central nervous system tissues. 1066 63

Tuberous sclerosis (TSC) is an autosomal dominant disorder characterized by a broad phenotypic spectrum that includes seizures, mental retardation, renal dysfunction and dermatological abnormalities. Inactivating mutations to either of the TSC1 and TSC2 tumour suppressor genes are responsible for the disease. TSC1 and TSC2 encode two large novel proteins called hamartin and tuberin, respectively. Hamartin and tuberin interact directly with each other and it has been reported that tuberin may act as a chaperone, preventing hamartin self-aggregation and maintaining the tuberin-hamartin complex in a soluble form. In this study, the ability of tuberin to act as a chaperone for hamartin was used to investigate the tuberin-hamartin interaction in more detail. A domain within tuberin necessary for the chaperone function was identified, and the effects of TSC2 missense mutations on the tuberin-hamartin interaction were investigated to allow specific residues within the central domain of tuberin that are important for the interaction with hamartin to be pin-pointed. In addition, the results confirm that phosphorylation may play an important role in the formation of the tuberin-hamartin complex. Although mutations that prevent tuberin tyrosine phosphorylation also inhibit tuberin-hamartin binding and the chaperone function, our results indicate that only hamartin is phosphorylated in the tuberin-hamartin complex.
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PMID:TSC2 missense mutations inhibit tuberin phosphorylation and prevent formation of the tuberin-hamartin complex. 1174 32

Tuberous sclerosis complex (TSC) is an autosomal dominant tumor predisposition syndrome characterized by benign proliferations (hamartomas). In the brain, individuals with TSC develop autism, mental retardation and seizures associated with focal cortical dysplasias, subependymal nodules, and subependymal giant cell astrocytomas (SEGAs). We hypothesize that dysregulated astrocyte function due to mutations in the tumor suppressor genes, TSC1 and TSC2, may contribute to the pathogenesis of these brain abnormalities. In this report, we demonstrate that mice heterozygous for a targeted defect in either the Tsc1 or Tsc2 genes(Tsc1+/- and Tsc2+/- mice) exhibit a 1.5-fold increase in the number of astrocytes in vivo. Whereas increased astrocyte numbers in vivo were suggestive of a proliferative advantage, Tsc2+/- primary astrocyte cultures did not show a cell-autonomous growth advantage, anchorage-independent growth, increased saturation density, or increased fluid-phase endocytosis compared to wild type astrocytes. Tsc2 null mouse embryonic fibroblasts (MEFs) however, did exhibit increased saturation density compared to Tsc2 wild type controls. In both Tsc2+/- astrocytes and Tsc2 null mouse embryonic fibroblasts, p27-Kip1 expression was decreased compared to wild type cells, and was reversed by tuberin re-expression in Tsc2-/- MEFs. In contrast, no change in endocytosis was observed upon tuberin re-expression in Tsc2-/- MEFs. Collectively, these results suggest Tsc heterozygosity may provide a non-cell-autonomous growth advantage for astrocytes that may involve p27-Kip1 expression.
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PMID:Heterozygosity for the tuberous sclerosis complex (TSC) gene products results in increased astrocyte numbers and decreased p27-Kip1 expression in TSC2+/- cells. 1203 87

Tuberous sclerosis is caused by mutations to either the TSC1 or TSC2 tumor suppressor gene. The disease is characterized by a broad phenotypic spectrum that includes seizures, mental retardation, renal dysfunction, and dermatological abnormalities. TSC1 encodes a 130-kDa protein called hamartin, and TSC2 encodes a 200-kDa protein called tuberin. Although it has been shown that hamartin and tuberin form a complex and mediate phosphoinositide 3-kinase/Akt-dependent phosphorylation of the ribosomal protein S6, it is not yet clear how inactivation of either protein leads to tuberous sclerosis. Therefore, to obtain additional insight into tuberin and hamartin function, yeast two-hybrid screening experiments were performed to identify proteins that interact with tuberin. One of the proteins identified was 14-3-3zeta, a member of the 14-3-3 protein family. The interaction between tuberin and 14-3-3zeta was confirmed in vitro and by co-immunoprecipitation; multiple sites within tuberin for 14-3-3zeta binding were identified; and it was determined that 14-3-3zeta associated with the tuberin-hamartin complex. Finally, it was shown that the tuberin/14-3-3zeta interaction is regulated by Akt-mediated phosphorylation of tuberin, providing insight into how tuberin may regulate phosphorylation of S6.
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PMID:Identification and characterization of the interaction between tuberin and 14-3-3zeta. 1217 84


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