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At least 19 recordsLinked to original sources
PubMed1999

Mutational analysis of TSC1 and TSC2 genes in Japanese patients with tuberous sclerosis complex.

We have surveyed the mutations of TSC1 and TSC2 from 38 (25 sporadic, 11 familial, and 2 unknown) Japanese patients with tuberous sclerosis complex. In 23 of 38 subjects, we detected 18 new mutations in addition to 4 mutations that had been previously reported. We also found 3 new polymorphisms. The mutations were not clustered on a particular exon in either of the genes. Seven TSC1 mutations found in 3 familial and 4 sporadic cases were on the exons (3 missense, 2 nonsense point mutations, a 1-base insertion, and a 2-bp deletion). Fifteen TSC2 mutations were found in 5 familial cases, 10 sporadic cases, and 1 unknown case. The 12 mutations were on the exons (8 missense, 1 nonsense point mutations, a 1-bp insertion, a 5-bp deletion, and a 4-bp replacement) and 3 point mutations were on the exon-intron junctions. Although the patients with TSC2 mutations tend to exhibit relatively severe mental retardation in comparison to those with TSC1 mutations, a genotype-phenotype correlation could not yet be established. The widespread distribution of TSC1/TSC2 mutations hinders the development of a simple diagnostic test, and the identification of individual mutations does not provide the prediction of prognosis.

Adolescent↗
PubMed2003

[Analysis of gene mutation in patients with tuberous sclerosis complex with polymerase chain reaction-single strand conformation polymorphism].

OBJECTIVE: Tuberous sclerosis complex (TSC) is an autosomal dominant disease characterized by unusual tumor-like growth, termed hamartomas that develop in a variety of tissues and organs. Clinical findings characteristic of TSC include facial angiofibroma, epilepsy and mental retardation. In the last decade, two genes (TSC1 and TSC2) responsible for this disease were identified and both of them are speculated to be a kind of tumor suppressor gene. TSC1 and TSC2 are located on 9q34 and 16p13.3, respectively. This study was designed to detect gene mutations in patients with TSC. METHODS: All the exons of TSC1 and TSC2 were analyzed by using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) in DNA separated from peripheral blood of 28 patients with TSC and 100 normal controls. Of the 28 patients, 17 were male and 11 were female, the age of the patients was 1 - 48 years. RESULTS: The mutations were not clustered on a particular exon in either of the genes. Four TSC1 mutations found in 28 cases were on exons (1 nonsense, 2 missense and 1 frameshift); 13 mutations were found in TSC2 gene (2 nonsense, 2 frameshift, 1 deletion and 8 missense). Both TSC1 and TSC2 mutations were detected in 2 cases respectively. The same missense mutation (Q654E) was found in 2 unrelated patients. There was no obvious relationship between the location of the mutation and the clinical symptoms. CONCLUSION: Mutations found in this study were distributed on various exons and there was no clustering of the mutations, the widespread distribution of TSC1/TSC2 mutations hinders the development of a simple diagnostic test, and the identification of individual mutations does not provide prediction of prognosis.

Adolescent↗
PubMed2000

The TSC1 gene product, hamartin, negatively regulates cell proliferation.

Tuberous sclerosis is an autosomal dominant hereditary disease caused by mutations in either the TSC1 or the TSC2 tumor suppressor gene. The TSC1 gene on chromosome 9q34 encodes a 130 kDa protein named hamartin, and the TSC2 gene on chromosome 16p13.3 codes for tuberin, a 200 kDa protein. Here we show that expression of hamartin, assayed by immunoblot analyses, is high in G(0)-arrested cells and hamartin is expressed throughout the entire ongoing cell cycle. An interaction of hamartin and tuberin can be detected in every phase of the cell cycle. Ectopic expression of high levels of hamartin attenuates cellular proliferation. We provide evidence that this effect could depend on a coiled-coil region earlier proposed to be involved in binding of hamartin to tuberin. Further investigations revealed that hamartin affects cell proliferation via deregulation of G(1) phase. Our data have a clear impact on understanding the role of hamartin during development of this disease.

Animals↗
PubMed1998

Carcinomalike monotypic epithelioid angiomyolipoma in patients without evidence of tuberous sclerosis: a clinicopathologic and genetic study.

We report the clinicopathologic, immunohistochemical, ultrastructural, and genetic features of an unusual renal tumor composed of large, atypical, densely packed, clear/eosinophilic epithelioid cells. Three patients, two men and one woman (ages 31, 36, and 60 years of age, respectively), had abdominal pain. Morphologically, all cases showed aggressive features (largeness, atypical cells, sarcomatoid features, necrosis, and, in one case, invasion of the renal vein). Despite the marked morphologic resemblance of these tumors to high-grade sarcomatoid renal cell carcinoma, their phenotype (HMB45+, CD68+/-, actin+/-, and vimentin and keratin negative) is in contrast to that observed in epithelial tumors and parallels the phenotypic profile of angiomyolipoma. Ultrastructural analysis showed the presence of glycogen, mitochondria, and prominent electron-dense, membrane-bound granules in the neoplastic cells, and the absence of melanosomes or premelanosomes. Genetic study, performed using polymerase chain reaction from paraffin sections, showed a loss of heterozygosity at the TSC2-containing region on 16p in one case, and on 3p in two cases, showing that multiple genetic alterations are taking place in these tumors. Follow-up has shown local recurrence in one case after 6 years, and the patient died 1 year later of cardiorespiratory failure. The other two patients are well after 26 and 10 months. All three patients were evaluated for signs of tuberous sclerosis, and findings were negative. We suggest that these tumors should be considered close relatives of the angiomyolipoma variants, composed purely of perivascular epithelioid cells. More cases and longer follow-up durations are needed to fully evaluate its prognostic implication.

Adult↗
PubMed2003

The cell cycle and tuberous sclerosis.

Tuberous sclerosis (TSC) is an autosomal dominant tumor suppressor gene syndrome occurring in about 1 in 6000 live births. Two genes have been shown to be responsible for this disease: TSC1 on chromosome 9q34, encoding hamartin, and TSC2 on chromosome 16p13.3, encoding tuberin. Although several different functions of these proteins have been described, the molecular mechanism for the development of TSC remains elusive. Mammalian and Drosophila TSC genes have been shown to be involved in cell cycle regulation. The Drosophila TSC genes have further been demonstrated to affect cell size control and to be related to the insulin signaling pathway. Very recent data provide evidence that mammalian TSC genes are also involved in cell size regulation.

Animals↗
PubMed1998

Hamartin, the product of the tuberous sclerosis 1 (TSC1) gene, interacts with tuberin and appears to be localized to cytoplasmic vesicles.

Tuberous sclerosis is an inherited syndrome associated with mutations in two tumor suppressor genes: TSC1 and TSC2. Tuberin, the product of TSC2, appears to be localized to the Golgi apparatus and may have a function in vesicular transport. The function of hamartin, the product of TSC1, is not known. In this report, we demonstrate an interaction between hamartin and tuberin, which is detectable at endogenous protein levels. Hamartin is present in a cell line derived from the Eker rat that lacks functional tuberin, indicating that the stability of hamartin is not dependent on its interaction with tuberin. Hamartin is localized to the membrane/particulate (P100) fraction of cultured cells. The P100 localization is unchanged in the Eker cells. Finally, we show that at endogenous expression levels, hamartin has a punctate pattern of immunofluorescence in the cytoplasm. Taken together, the presence of hamartin in the membrane/particulate fraction and its pattern of cytoplasmic staining suggest that it is localized to cytoplasmic vesicles. If altered vesicular trafficking leads to tumorigenesis in tuberous sclerosis, TSC1 and TSC2 may have a novel mechanism of tumor suppression.

Animals↗
PubMed2003

Tuberous sclerosis genes regulate cellular 14-3-3 protein levels.

The genes TSC1, encoding hamartin, and TSC2, encoding tuberin are responsible for tuberous sclerosis. This autosomal dominant tumor suppressor gene syndrome affects about 1 in 6000 individuals. A variety of tumors characteristically occur in different organs of tuberous sclerosis patients and are believed to result from defects in cell cycle/cell size control. We performed a proteomics approach of two-dimensional gel electrophoresis with subsequent mass spectrometrical identification of protein spots after ectopic overexpression of human TSC1 or TSC2. We found the cellular levels of four isoforms of the 14-3-3 protein family, 14-3-3 gamma, 14-3-3, 14-3-3 sigma, and 14-3-3 zeta, to be regulated by the two tuberous sclerosis gene products. In the same experiments the protein levels of keratin 7, capZ alpha-1 subunit, ezrin, and nedasin were not affected by ectopic TSC1 or TSC2. Western blot analyses confirmed the deregulation of 14-3-3 proteins upon ectopic overexpression of TSC1 and TSC2. A TSC1 mutant not encoding the transmembrane domain and the tuberin-binding domain but harbouring most of the coiled-coil region and the ERM protein interaction domain of hamartin did not affect 14-3-3 protein levels. The here presented findings suggest that deregulation of 14-3-3 protein amounts might contribute to the development of tumors in tuberous sclerosis patients. These data provide important new insights into the molecular development of this disease especially since both, the TSC genes and the 14-3-3 proteins, are known to be involved in mammalian cell cycle control.

14-3-3 Proteins↗
PubMed1999

Analysis of both TSC1 and TSC2 for germline mutations in 126 unrelated patients with tuberous sclerosis.

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by the development of multiple hamartomas involving many organs. About two-thirds of the cases are sporadic and appear to represent new mutations. With the cloning of two causative genes, TSC1 and TSC2 it is now possible to analyze both genes in TSC patients and identify germline mutations. Here we report the mutational analysis of the entire coding region of both TSC1 and TSC2 genes in 126 unrelated TSC patients, including 40 familial and 86 sporadic cases, by single-stranded conformational polymorphism (SSCP) analysis followed by direct sequencing. Mutations were identified in a total of 74 (59%) cases, including 16 TSC1 mutations (5 sporadic and 11 familial cases) and 58 TSC2 mutations (42 sporadic and 16 familial cases). Overall, significantly more TSC2 mutations were found in our population, with a relatively equal distribution of mutations between TSC1 and TSC2 among the familial cases, but a marked underrepresentation of TSC1 mutations among the sporadic cases (P = 0.0035, Fisher's exact test). All TSC1 mutations were predicted to be protein truncating. However, in TSC2 13 missense mutations were found, five clustering in the GAP-related domain and three others occurring in exon 16. Upon comparison of clinical manifestations, including the incidence of intellectual disability, we could not find any observable differences between TSC1 and TSC2 patients. Our data help define the distribution and spectrum of mutations associated with the TSC loci and will be useful for both understanding the function of these genes as well as genetic counseling in patients with the disease.

Codon, Nonsense↗
PubMed2001

Hamartin expression and interaction with tuberin in tumor cell lines and primary cultures.

Tuberous sclerosis (TSC) is a neurocutaneous disorder characterized by multi-system hamartomatous lesions, and results from a mutation in TSC1, that encodes hamartin, or TSC2, that encodes tuberin. We have examined hamartin expression in a diverse range of human and rat cell lines and primary cultured cells derived from tissues that express hamartin in vivo. Strong hamartin signal was detected in every cell line of human origin examined, representing neuronal, epithelial, lymphoid, renal, vascular smooth muscle, liver, and prostatic cells. Primary cell cultures of oligodendroglioma, meningioma, and glioblastoma multiforme origin were also found to express hamartin. Hamartin was also detected in the rat PC12 cell line, as well as purified primary cultures of rat cortical neurons, astrocytes, and oligodendroglia, with a stronger signal found in astrocytes. Using co-immunoprecipitation, we have also confirmed the physical interaction of tuberin and hamartin in a diverse range of human and rat cell types. These findings demonstrate that hamartin is widely expressed in human and rat cell lines and cultures, and demonstrate that hamartin expression is not lost during the establishment of tumor cell lines or primary cultures. This suggests that the cell lines and cultures studied may serve as useful in vitro models for biochemical investigations involving hamartin and tuberin both individually and as a complex, as well as studies to elucidate the mechanisms underlying the organ-specific pathology of TSC.

Animals↗
PubMed2003

Markers of cellular proliferation are expressed in cortical tubers.

p34cdc2, collapsin response mediator protein 4 (CRMP4), doublecortin (DCX), HuD, and NeuN expression was assessed in tuber (n = 16) and subependymal giant cell astrocytoma (SEGA; n = 6) specimens in tuberous sclerosis complex to define the developmental phenotype and lineage of giant cells (CGs) in these lesions. Many GCs exhibited HuD and NeuN immunolabeling suggesting a differentiated neural phenotype. Giant cells in tubers, SEGAs and subependymal nodules in the Eker rat model of TSC expressed CRMP4 and DCX. Tubers and SEGAs exhibit a heterogeneous profile of differentiation and may share a common cellular lineage. Tubers may contain a subpopulation of newly generated cells.

Blotting, Western↗
PubMed2003

Metastasis of benign tumor cells in tuberous sclerosis complex.

Lymphangiomyomatosis (LAM) is a life-threatening lung disease affecting almost exclusively young women. Histologically, LAM is characterized by the diffuse, bilateral proliferation of abnormal smooth muscle cells and cystic degeneration of the lung parenchyma. LAM can occur as an isolated disorder (sporadic LAM), or in women with tuberous sclerosis complex (TSC-LAM). Patients with both sporadic LAM and TSC-LAM often have benign renal angiomyolipomas. The smooth muscle cells within the angiomyolipomas are very similar to the smooth muscle cells in pulmonary LAM. Genetic data suggest that pulmonary LAM is the result of a highly unusual disease mechanism: the metastasis of benign cells. If LAM is the result of metastasis, it is remarkable that the metastasis occurs in women, but not in men. In this review, I discuss the genetic data supporting this metastatic model for LAM. The implications of the model for the functions of the TSC1 and TSC2 gene products, hamartin and tuberin, respectively, will also be considered. Hamartin and tuberin may play functional roles in the suppression of cell migration and/or metastasis, possibly through their regulation of the small GTPase Rho.

Animals↗
PubMed2003

Multiple roles of the tuberous sclerosis complex genes.

Soon after proposing the "two-hit" hypothesis for tumorigenesis, Knudson pursued further experimental validation of the concept by using a rat model of dominantly inherited renal tumor. Today, the Eker rat is one of the best characterized models of tuberous sclerosis complex (TSC) and has been used extensively for study of the function of the TSC2 tumor suppressor gene. Along with TSC1, these two genes behave as expected for tumor suppressor genes with evidence for loss of heterozygosity in tumors and suppression of growth when expressed in proliferating cells. Despite much experimental work, the mechanisms of these genes have remained elusive until recently. This review summarizes some of the current concepts in our understanding of the biological and biochemical function of the TSC genes.

Animals↗
PubMed2003

Characterizing mutations in samples with low-level mosaicism by collection and analysis of DHPLC fractionated heteroduplexes.

Somatic mosaicism is a frequent phenomenon in mendelian disorders that exhibit a high proportion of new mutations; however, mutant alleles present at low frequency are difficult to detect and characterize. We have previously shown that denaturing high-performance liquid chromatography (DHPLC) can detect TSC1 and TSC2 mutations in tuberous sclerosis patients with low-level somatic mosaicism, even when direct sequencing cannot identify the causative lesion. Characterization of these mutations traditionally involves extensive sequencing of cloned products. To overcome this limitation, we have utilized DHPLC with an in-line fraction collector to isolate low-level heteroduplex peaks that can be directly sequenced to reveal the mutation. We have successfully applied this technique to resolve the mutations 2724-1G>C in TSC1and 1462-28del42bp, 1774del4bp, and N1643K (4947C>G) in TSC2, which were present in only 6.5-17% of the patients' alleles. We have also applied this technique to successfully resolve seven somatic APC mutations in colorectal tumor samples that were previously undetectable by direct PCR product sequencing. This method may simplify many of the currently challenging goals in mutation detection.

Chromatography, High Pressure Liquid↗
PubMed2000

Expression of the tuberous sclerosis complex gene products, hamartin and tuberin, in central nervous system tissues.

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.

Animals↗
PubMed2001

Developmental expression of the tuberous sclerosis proteins tuberin and hamartin.

Tuberous sclerosis complex is an autosomal dominant multisystem disorder, characterized by the development of hamartomas in multiple organs, primarily the skin, heart, kidney, and brain. The tuberous sclerosis genes, TSC1 and TSC2, encode hamartin and tuberin, respectively. Employing specific antibodies for hamartin and tuberin, we analyzed the expression of these two proteins by Western blot analyses in normal developing human and rat tissues. Both proteins are expressed ubiquitously in human fetal tissues and placenta, but are expressed at relatively low levels in human adult tissues, except brain. Similarly, high expression of these two proteins is observed in rat embryonic tissues, with a progressive decline after birth. To better characterize the developmental expression of tuberin and hamartin, we conducted a detailed study in rat tissues from embryonic day 13 to adult by Western blot analysis and immunohistochemistry. Immunohistochemical staining of rat tissues for tuberin and hamartin revealed tissue-specific expression patterns throughout development. Both tuberin and hamartin are expressed in epithelia, muscle (smooth, cardiac and skeletal muscle) and the nervous system (neurons, glia, choroid plexus and arachnoid). Except for the central nervous system, immunostaining intensity declines with age, confirming the protein blot analysis. These results indicate that tuberin and hamartin may play a critical role in development, and thus provide a framework for understanding the developmental and hamartomatous manifestations of tuberous sclerosis. These findings also suggest that tuberin and hamartin have additional functions in the adult brain, consistent with the marked neurological problems that afflict many patients with tuberous sclerosis.

Age Factors↗
PubMed2000

Simultaneous loss of hamartin and tuberin from the cerebrum, kidney and heart with tuberous sclerosis.

Tuberous sclerosis (TSC) is caused by a mutation in either the TSC1 or TSC2 gene. The clinical manifestations of mutations of the two genes are hardly distinguishable, for reasons as yet unknown. In this study, we examined the expression of the products of these genes, hamartin and tuberin, in control and TSC tissues. Western blotting disclosed that hamartin and tuberin are both abundant in the cerebral gray matter and that they have similar subcellular distributions and developmental patterns of expression. Immunohistochemical localizations of hamartin and tuberin were also similar, with high levels of expression being localized to the cerebral neurons and glial cells, renal uriniferous and collecting tubules, and cardiac muscles. In the cerebrum with TSC, both hamartin and tuberin were simultaneously reduced in the cortical tubers and subependymal giant cell astrocytomas, and from the normal-appearing cortex. The renal angiomyolipomas and cardiac rhabdomyomas also showed a loss of both the proteins. These results provide evidence for the co-localization and interaction of hamartin and tuberin in vivo, and suggest that a mutation in one TSC gene may secondarily affect the expression of the other in some TSC lesions.

Adolescent↗