Mutations In Tuberous Sclerosis Complex Research Articles

A distinct microRNA expression profile is associated with α[11C]-methyl-L-tryptophan (AMT) PET uptake in epileptogenic cortical tubers resected from patients with tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is characterized by hamartomatous lesions in various organs and arises due to mutations in the TSC1 or TSC2 genes. TSC mutations lead to a range of neurological manifestations including epilepsy, cognitive impairment, autism spectrum disorders (ASD), and brain lesions that include cortical tubers. There is evidence that seizures arise at or near cortical tubers, but it is unknown why some tubers are epileptogenic while others are not. We have previously reported increased tryptophan metabolism measured with α[11C]-methyl-l-tryptophan (AMT) positron emission tomography (PET) in epileptogenic tubers in approximately two-thirds of patients with tuberous sclerosis and intractable epilepsy. However, the underlying mechanisms leading to seizure onset in TSC remain poorly characterized. MicroRNAs are enriched in the brain and play important roles in neurodevelopment and brain function. Recent reports have shown aberrant microRNA expression in epilepsy and TSC. In this study, we performed microRNA expression profiling in brain specimens obtained from TSC patients undergoing epilepsy surgery for intractable epilepsy. Typically, in these resections several non-seizure onset tubers are resected together with the seizure-onset tubers because of their proximity. We directly compared seizure onset tubers, with and without increased tryptophan metabolism measured with PET, and non-onset tubers to assess the role of microRNAs in epileptogenesis associated with these lesions. Whether a particular tuber was epileptogenic or non-epileptogenic was determined with intracranial electrocorticography, and tryptophan metabolism was measured with AMT PET. We identified a set of five microRNAs (miR-142-3p, 142-5p, 223-3p, 200b-3p and 32-5p) that collectively distinguish among the three primary groups of tubers: non-onset/AMT-cold (NC), onset/AMT-cold (OC), and onset/AMT-hot (OH). These microRNAs were significantly upregulated in OH tubers compared to the other two groups, and microRNA expression was most significantly associated with AMT-PET uptake. The microRNAs target a group of genes enriched for synaptic signaling and epilepsy risk, including SLC12A5, SYT1, GRIN2A, GRIN2B, KCNB1, SCN2A, TSC1, and MEF2C. We confirmed the interaction between miR-32-5p and SLC12A5 using a luciferase reporter assay. Our findings provide a new avenue for subsequent mechanistic studies of tuber epileptogenesis in TSC.

Cerebellar lesions are associated with TSC2 mutations in tuberous sclerosis complex: a retrospective record review study.

Cerebellar lesions are present in approximately 30% of patients with tuberous sclerosis complex. Although several prior studies have characterized these lesions, our study provides the first description of the specific distribution of these lesions within the cerebellum and the first genotype-phenotype correlation yet to be published. We retrospectively reviewed magnetic resonance images from 220 paediatric and adult patients with tuberous sclerosis complex (95 males, 125 females; mean age 22.7y, range 9mo-81y). Sex, age, and genotype of patients with cerebellar lesions were recorded and specific characteristics, including signal intensity, number, shape, presence of enhancement, calcification or haemorrhage, and location within the cerebellar lobules were noted. Fifty-eight patients (26.4%) had 106 cerebellar lesions (62 right, 44 left). The mean number of cerebellar lesions per patient was 1.8 (range 1-6). Enhancement was present in 42.4% of lesions and folial retraction in 84%. Calcification was detected in 86.8% of lesions. Patients with calcified lesions were older (mean age 21.6y) than patients without calcification (11.5y). TSC2 mutations were detected in 41/42 (97.6%) of patients with cerebellar tubers who had genetic testing and one patient had no mutation identified. None of the patients had TSC1 mutation. We provide new information regarding cerebellar lesions in tuberous sclerosis complex: cerebellar lesions are significantly much more frequent in patients with TSC2 mutations than TSC1 mutations or patients with no mutation identified, and Crus II is the most frequent location of cerebellar lesions. New studies are needed to assess the clinical significance of these lesions.

Inhibition of ERK1/2 Restores GSK3\u03b2 Activity and Protein Synthesis Levels in a Model of Tuberous Sclerosis

Tuberous sclerosis (TS) is a multi-organ autosomal dominant disorder that is best characterized by neurodevelopmental deficits and the presence of benign tumors. TS pathology is caused by mutations in tuberous sclerosis complex (TSC) genes and is associated with insulin resistance, decreased glycogen synthase kinase 3β (GSK3β) activity, activation of the mammalian target of rapamycin complex 1 (mTORC1), and subsequent increase in protein synthesis. Here, we show that extracellular signal–regulated kinases (ERK1/2) respond to insulin stimulation and integrate insulin signaling to phosphorylate and thus inactivate GSK3β, resulting in increased protein synthesis that is independent of Akt/mTORC1 activity. Inhibition of ERK1/2 in Tsc2−/− cells—a model of TS—rescues GSK3β activity and protein synthesis levels, thus highlighting ERK1/2 as a potential therapeutic target for the treatment of TS.

What's new with common genetic skin disorders?

Familiar genetic disorders such as neurofibromatosis type I (NF1), tuberous sclerosis complex (TSC), oculocutaneous albinism (OCA), basal cell nevus syndrome (BCNS), incontinentia pigmenti, ichthyosis, and epidermolysis bullosa (EB) have prominent, cutaneous manifestations. This review describes recent advances in knowledge concerning the pathophysiology, diagnosis, and treatment of these skin features. Specifically, clinical diagnostic criteria for incontinentia pigmenti, ichthyosis, and tuberous sclerosis have been updated. Additionally, there have been considerable advancements in the technology used in the molecular diagnoses of these conditions. In the case of TSC, the discovery that a portion of TSC mutations are missed due to mosaicism is driving the development of new diagnostic methods. Also, scientists are also seeking minimally invasive methods of genetic diagnosis, as in the case of using hair follicles to diagnose autosomal recessive congenital ichythosis (ARCI). Finally, there are innovative targeted medical therapies being developed that serve as promising tools in the care of patients afflicted with conditions including ichthyosis and EB.

Abnormal Neural Progenitor Cells Differentiated from Induced Pluripotent Stem Cells Partially Mimicked Development of TSC2 Neurological Abnormalities.

SummaryTuberous sclerosis complex (TSC) is a disease featuring devastating and therapeutically challenging neurological abnormalities. However, there is a lack of specific neural progenitor cell models for TSC. Here, the pathology of TSC was studied using primitive neural stem cells (pNSCs) from a patient presenting a c.1444-2A>C mutation in TSC2. We found that TSC2 pNSCs had higher proliferative activity and increased PAX6 expression compared with those of control pNSCs. Neurons differentiated from TSC2 pNSCs showed enlargement of the soma, perturbed neurite outgrowth, and abnormal connections among cells. TSC2 astrocytes had increased saturation density and higher proliferative activity. Moreover, the activity of the mTOR pathway was enhanced in pNSCs and induced in neurons and astrocytes. Thus, our results suggested that TSC2 heterozygosity caused neurological malformations in pNSCs, indicating that its heterozygosity might be sufficient for the development of neurological abnormalities in patients.

Lymphangioleiomyomatosis: A Monogenic Model of Malignancy.

Lymphangioleiomyomatosis (LAM) is a rare, low-grade, metastasizing neoplasm that arises from an unknown source, spreads via the lymphatics, and targets the lungs. All pulmonary structures become infiltrated with benign-appearing spindle and epithelioid cells (LAM cells) that express smooth-muscle and melanocyte-lineage markers, harbor mTOR-activating mutations in tuberous sclerosis complex (TSC) genes, and recruit abundant stromal cells. Elaboration of lymphangiogenic growth factors and matrix remodeling enzymes by LAM cells enables their access to lymphatic channels and likely drives the cystic lung remodeling that often culminates in respiratory failure. Dysregulated cellular signaling results in a shift from oxidative phosphorylation to glycolysis as the preferred mode of energy generation, to allow for the accumulation of biomass required for cell growth and tolerance of nutrient-poor, anaerobic environments. Symptomatic LAM occurs almost exclusively in females after menarche, highlighting the central but as yet poorly understood role for sex-restricted anatomical structures and/or hormones in disease pathogenesis. LAM is an elegant model of malignancy because biallelic mutations at a single genetic locus confer all features that define cancer upon the LAM cell-metabolic reprogramming and proliferative signals that drive uncontrolled growth and inappropriate migration and invasion, the capacity to exploit the lymphatic circulation as a vehicle for metastasis and access to the lungs, and destruction of remote tissues. The direct benefit of the study of this rare disease has been the rapid identification of an effective FDA-approved therapy, and the collateral benefits have included elucidation of the pivotal roles of mTOR signaling in the regulation of cellular metabolism and the pathogenesis of cancer.

An estimation of the incidence of tuberous sclerosis complex in a nationwide retrospective cohort study (1997-2010).

Tuberous sclerosis complex (TSC) is caused by mutations in TSC1 and TSC2, leading to mammalian target of rapamycin hyperactivation. Patients with TSC develop hamartomas in brain, lungs, liver and skin. Two epidemiological studies, performed in Minnesota, U.S.A., have estimated the incidence of TSC to be 0·28-0·56 per 100 000 person-years (PY), based on < 12 patients. Furthermore, whether common comorbidities are associated with this rare disease is not known. To estimate the incidence of TSC and investigate the associations of TSC with other comorbidities, including diabetes, peptic ulcers, stroke and myocardial infarction. We estimated the incidence and prevalence of TSC and its comorbidities from 1997 to 2010, based on the Catastrophic Illness Certificate disease database and a beneficiary cohort of 1 million people. The incidence of TSC in Taiwan is 0·153 per 100 000 PY. The number of patients identified with TSC in Taiwan doubled from 206 in 2006 to 471 in 2010. In 2010, the prevalence of TSC in Taiwan was estimated to be 1·58 in 100 000. We confirmed that female patients with TSC are more likely to develop renal tumours than male patients. Surprisingly, patients with TSC have a significantly decreased risk of developing peptic ulcers compared with controls. This is the first large-scale and longitudinal incidence study of TSC. This study provides compelling evidence that TSC mutations in humans are associated with a decreased risk of peptic ulcers.

Detection of TSC1/TSC2 gene mutations among patients with tuberous sclerosis complex by Ion Torrent semiconductor sequencing

To develop and validate a method for mutation screening and prenatal diagnosis of TSC1/TSC2 mutations among patients with tuberous sclerosis complex (TSC) by Ion Torrent semiconductor sequencing. Potential mutations of SC1/TSC2 gene was detected in 2 TSC families and 1 sporadic TSC patient using an Ion Torrent PGM sequencer. Candidate variants were validated by Sanger sequencing. The corresponding site of TSC2 in the fetus of family 2 was also detected with Sanger sequencing. Ion Torrent semiconductor sequencing has identified a probably pathogenic TSC2 mutation (c.311-312insGCTG) in the patient from family 1, and a probably pathogenic TSC2 mutation (c.1790A>G) in the patient of family 2. Targeted Ion Torrent PGM sequencing is an accurate and efficient method to detect TSC1/TSC2 mutations in TSC.

The Stress-Induced Atf3-Gelsolin Cascade Underlies Dendritic Spine Deficits in Neuronal Models of Tuberous Sclerosis Complex.

Tuberous sclerosis complex (TSC) is a genetic disease associated with epilepsy and autism. Dysregulated protein synthesis has been implicated as a cause of this disease. However, cell type-specific translational profiles that are aberrant in this disease are unknown. Here we show that expression of many stress and/or activity-dependent proteins is highly induced while some synaptic proteins are repressed in neurons missing the Tsc2 gene expression. Identification of genes whose translation is abnormal in TSC may provide insights to previously unidentified therapeutic targets.

LAM/TSC Cell Migration to Uterus in an Experimental Model of Lymphangioleiomyomatosis. Regulation by Anti-Epidermal Growth Factor Receptor Antibody and Rapamycin

Lymphangioleiomyomatosis (LAM) is a rare lung disease affecting almost exclusively women, characterized by the invasion and abnormal proliferation of smooth muscle-like cells in pulmonary parenchyma and axial lymphatics. LAM cells bear mutations in Tuberous Sclerosis Complex (TSC) genes. It has been hypothesized that uterus might be the primary site of origin and one of the most frequent metastatic or disseminated site of LAM cells. We developed a mouse model to study the migratory and invasive properties of human LAM/TSC cells to the uterus. We also examined the action of rapamycin and anti-Epidermal Growth Factor Receptor (EGFR) antibody. LAM/TSC cells were endonasally administered to 3 week old immunodeficient female nude mice. 5 months later mice were divided in 4 groups: control, LAM/TSC cell-administered mice, LAM/TSC cell-administered mice treated with rapamycin, and LAM/TSC cell-administered mice treated with anti-EGFR antibody. Drugs were administered for one months. Uteri were analysed for the presence of human LAM/TSC cells by COX IV antibody, lymphangiogenesis by LYVE 1 expression and angiogenesis by counting blood vessels. LAM/TSC cells migrated to the uterus without causing any morphological lesion. Interestingly, LAM/TSC cells increased the number of blood vessels while did not cause any alteration in lymphatics vessels. Anti-EGFR antibody and rapamycin reduced the number of human LAM/TSC and counteracted the proliferation of blood vessels in uteri. Although both drugs did not change the expression of LYVE 1, localization of lymphatics was mainly in the perimetrium after drug treatment. Our data describe the strong invasive capability of human LAM/TSC cells which migrated to the uterus. LAM/ TSC cells presence is accompanied by increased angiogenesis. Anti-EGFR antibody and rapamycin were effective in reducing the LAM/TSC cell number and blood vessel proliferation.

TSC2 Deletions and Duplications: A Descriptive Study in Iranian Patients Affected with Tuberous Sclerosis

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by formation of benign tumors called hamartomas. Although the TSC is diagnosed based on clinical findings but approximately 85% of individuals who meet diagnostic criteria for TSC a mutation can be identified in TSC2 (69%) and TSC1 (31%). A review of mutation type in TSC1 & TSC2 genes reveals that deletion/duplication assay could be a good screening strategy as a first step in TSC molecular diagnosis. All 41 exons and 5’ untranslated region of TSC2 gene in addition to adjacent PKD1 gene were screened for deletion/duplication in 81 patients DNA samples using multiplex ligation dependent probe amplification (MLPA) method. Deletion/duplication was found in 29 (35.8%) patients, including deletions in 26 (32.0%) patients and duplication in 3 (3.8%). Genotype/phenotype analysis, showed five patients with renal function impairment who have large deletions including PKD gene area. Approximately 65% of cases were sporadic, while the remaining have familial positive history. Deletions/duplications of TSC2 gene were seen in 35.8% of patients with TSC. So it could be concluded that MLPA is a useful testing strategy for molecular screening in sporadic forms of TSC patients. MLPA increased the detection of TSC mutations. MLPA is less expensive, quicker and more precise than direct sequencing and southern blot in the characterization of TSC deletions. This technique is recommended as a standard part of TSC clinical molecular diagnosis.

Mutational analysis of TSC1 and TSC2 in Japanese patients with tuberous sclerosis complex revealed higher incidence of TSC1 patients than previously reported

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by multiple hamartias and hamartomas involving throughout the body. To date, many TSC1 and TSC2 mutations have been reported all over the world, however, few TSC mutation studies have been performed in the Japanese population, and genetic characteristics of Japanese TSC patients are not yet clear. In this study, we analyzed TSC1 and TSC2 in 57 Japanese patients with TSC (8 familial and 49 sporadic; 46 definite and 11 suspect TSC) and identified 31 mutations including 11 TSC1 mutations (two familial and nine sporadic; all definite TSC) and 20 TSC2 mutations (2 familial and 18 sporadic; 19 definite and 1 suspect TSC). We also reviewed all Japanese TSC mutations previously reported. Our study demonstrates significantly higher incidence (P=0.007) of TSC1 mutations among sporadic TSC patients in the Japanese population compared with US and European studies. No differences emerged in mutation distributions and types in precedent studies, excepting low frequency of the TSC2 nonsense mutation. Comparing clinical manifestations, developmental delay and/or mental retardation were milder in TSC1 patients than TSC2 patients for its frequency (P=0.032) and severity (P=0.015); however, no other symptoms were clearly different.

Dysregulation of mTOR Signaling in Neuropsychiatric Disorders: Therapeutic Implications

Autism is a widespread disorder characterized by deficits in social interactions, impairments in communication, and repetitive and stereotypic behaviors. Identification of genetic markers has proved difficult, owing to the highly complex and variable nature of the disease. Although autism spectrum disorders (ASDs) arise as a consequence of mutations in genes with multiple molecular functions, they appear to converge on common biological pathways to give rise to autism-relevant behaviors (Abrahams and Geschwind, 2008). One such pathway is the PI3K-mammalian target of rapamycin (mTOR) signaling cascade. The mTOR pathway is a central regulator of cell growth, proliferation, survival, and cap-dependent protein translation. In brain, components of the mTOR pathway are present at synapses, where they regulate dendritic spine morphology, and are essential to synaptogenesis. Growing evidence indicates that dysregulation of mTOR is involved in human diseases, including cancer, diabetes, and autism. Mutations in tuberous sclerosis complex (TSC)1, TSC2, neurofibromatosis 1 (NF1), and PTEN lead to overactivated PI3K-mTOR pathway, autism-relevant behaviors, and tuberous sclerosis, neurofibromatosis, or macrocephaly.

Mutation screening and prenatal diagnosis of tuberous sclerosis complex

To screen mutations of tuberous sclerosis complex (TSC) patients to confirm a clinical diagnosis of TSC, and to perform prenatal diagnosis for families with mutations. In this study, PCR-denaturing high-performance liquid chromatography(DHPLC), supplemented with sequencing when necessary, was used to screen TSC1 and TSC2 mutations in 21 patients from 19 pedigrees visited author's hospital in the last five years. For novel mutations, one hundred unrelated healthy individuals were screened to exclude the possibility of polymorphism. Seventeen different mutations were found in 21 patients of 19 pedigrees with 13 being novel mutations, including c. 2672delA, c. 2672insA of TSC1 gene and c.4918insCGCC, c.1143delG, Intron27+1 G>A, c.1957-1958delAG, Intron5+1 G>A, c.910insCT, c.2753 C>G, c.4078dupAGCAAGTCCAGCTCCTC, Intron 11 -1 G>A, Intron 14+1 G>A, c.684 C>A of TSC2 gene, indicating a high frequency of de novo mutations in TSC. Three of these mutations were in the TSC1 gene (N762S, c.2672insA and c. 2672delA), while all remaining 14 were in the TSC2 gene. Prenatal diagnosis for TSC was performed for 7 fetuses from these pedigrees. The six fetuses that tested negative for TSC mutations were carried to term and, to date, none of these children has shown symptoms of TSC. Author's data showed that a mutation detection rate of tuberous sclerosis was 89.5%(17/19) among patients in author's hospital. The ratio of TSC2 and TSC1 mutations was about 1:1 in the familial cases, but TSC2 mutation was more common than TSC1 mutation in sporadic cases. Author's data demonstrated that birth of TSC children for those with familial history of TSC could be prevented through prenatal diagnosis.

Ultra deep sequencing detects a low rate of mosaic mutations in tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal dominant neurocutaneous syndrome caused by mutations in TSC1 and TSC2. However, 10-15% TSC patients have no mutation identified with conventional molecular diagnostic studies. We used the ultra-deep pyrosequencing technique of 454 Sequencing to search for mosaicism in 38 TSC patients who had no TSC1 or TSC2 mutation identified by conventional methods. Two TSC2 mutations were identified, each at 5.3% read frequency in different patients, consistent with mosaicism. Both mosaic mutations were confirmed by several methods. Five of 38 samples were found to have heterozygous non-mosaic mutations, which had been missed in earlier analyses. Several other possible low-frequency mosaic mutations were identified by deep sequencing, but were discarded as artifacts by secondary studies. The low frequency of detection of mosaic mutations, two (6%) of 33, suggests that the majority of TSC patients who have no mutation identified are not due to mosaicism, but rather other causes, which remain to be determined. These findings indicate the ability of deep sequencing, coupled with secondary confirmatory analyses, to detect low-frequency mosaic mutations.

Utility of [18F]2-Fluoro-2-Deoxyglucose-PET in Sporadic and Tuberous Sclerosis-Associated Lymphangioleiomyomatosis

Mutations in tuberous sclerosis complex (TSC) genes are associated with dysregulated mammalian target of rapamycin (mTOR)/Akt signaling and unusual neoplasms called perivascular epithelioid cell tumors (PEComas), including angiomyolipomas (AMLs) and lymphangioleiomyomatosis (LAM). Tools that quantify metabolic activity and total body burden of AML and LAM cells would be valuable for the assessment of disease progression and the response to therapy in patients with TSC and LAM. Our hypothesis was that constitutive activation of mTOR in LAM and AML cells would result in increased glucose uptake of [(18)F]2-fluoro-2-deoxyglucose (FDG) on PET scanning, as has been suggested by a single prior case report. After institutional review board approval, FDG-PET scanning was performed in six LAM patients. Six additional LAM patients underwent FDG-PET scanning for clinical evaluation of suspected malignancy. Pleural uptake related to prior therapy was identified in four individuals with a remote history of talc pleurodesis. Focal increased uptake was observed in a supraclavicular lymph node in a patient with Hodgkin lymphoma and in a lung nodule in a patient with a biopsy-documented primary lung adenocarcinoma. In one TSC-LAM patient with a biopsy-documented malignant uterine PEComa, robust uptake was noted in metastatic nodules in the lung but not in the LAM-involved lung parenchyma or the patient's massive abdominal lymphangioleiomyomas. No abnormal uptake was identified in the AMLs or LAM lesions in any patients. This pilot study suggests that FDG-PET scans are negative in patients with benign PEComas and therefore are not likely to be useful for estimating the burden of disease in patients with TSC or LAM, but that FDG-PET scans can be used to identify or exclude other neoplasms in these patients.

Analysis of 65 tuberous sclerosis complex (TSC) patients byTSC2DGGE,TSC1/TSC2MLPA, andTSC1long-range PCR sequencing, and report of 28 novel mutations

Tuberous sclerosis complex (TSC) is a severe autosomal-dominant disorder characterized by the development of benign tumors (hamartomas) in many organs. It can lead to intellectual handicap, epilepsy, autism, and renal or heart failure. An inactivating mutation in either of two tumor-suppressor genes-TSC1 and TSC2-is the cause of this syndrome, with TSC2 mutations accounting for 80-90% of all mutations. Molecular diagnosis of TSC is challenging, since TSC1 and TSC2 consist of 21 and 41 coding exons, respectively, and the mutation spectrum is very heterogeneous. Here we report a new approach for detecting mutations in TSC: a denaturing gradient gel electrophoresis (DGGE) analysis for small TSC2 mutations, a multiplex ligation-dependent probe amplification (MLPA) analysis for large deletions and duplications in TSC1 or TSC2, and a long-range PCR/sequencing-based analysis for small TSC1 mutations. When applied in this order, the three methods provide a new sensitive and time- and cost-efficient strategy for the molecular diagnosis of TSC. We analyzed 65 Danish patients who had been clinically diagnosed with TSC, and identified pathogenic mutations in 51 patients (78%). These included 36 small TSC2 mutations, four large deletions involving TSC2, and 11 small TSC1 mutations. Twenty-eight of the small mutations are novel. For the missense mutations, we established a functional assay to demonstrate that the mutations impair TSC2 protein function. In conclusion, the strategy presented may greatly help small- and medium-sized laboratories in the pre- and postnatal molecular diagnosis of TSC.

Altered gene expression in phenotypically normal renal cells from carriers of tumor suppressor gene mutations

BACKGROUND: The inherently complex signaling networks of tumors result from genetic and epigenetic alterations that occur during cancer initiation and progression. METHODS: In an attempt to identify early molecular changes associated with dominantly inherited predisposition to “two-hit” renal tumors, the expression profiles of primary cultures of phenotypically normal renal epithelial cells from individuals bearing a germline mutation in either the von Hippel- Lindau (VHL) or the tuberous sclerosis complex (TSC) gene were compared to that of renal epithelial cells from control nonmutation carriers by microarray analysis. RESULTS: Reliability of the microarray data from pooled samples was confirmed by real-time RT-PCR. Principal Component Analysis revealed substantial differences in the gene expression profiles of the renal epithelial cells from VHL and TSC mutation carriers. In several instances, the microarray data confirm our present knowledge of the cellular pathways affected by biallelic VHL and TSC mutations. CONCLUSIONS: These findings demonstrate that heterozygosity for a mutant tumor suppressor gene may alter the expression profiles of phenotypically normal epithelial cells in a gene-specific manner. Detectable effects of “one-hit” represent early molecular changes in tumorigenesis that may serve as targets for chemopreventive intervention. Running Title: Gene Expression in Heterozygous TSC and VHL Renal Cells

Overexpression of tuberous sclerosis complex 2 exerts antitumor effect on oral cancer cell lines

Tuberous sclerosis is caused by mutations in tuberous sclerosis complex (TSC) 2 on chromosome 16p13.3, encoding tuberin which is thought to be essential for p27Kip1 to regulate the cell cycle. In this study, we conducted to examine whether overexpression of TSC2 can affect the growth of oral cancer cells which have different expression level of p27Kip1 protein. We constructed an expression vector containing sense-oriented rat TSC2 cDNA with pcDNA3.1. We transfected oral cancer cells, B88t (high expression of p27Kip1 protein) and HI (low expression of p27Kip1 protein) with the sense expression vector to up-regulate the expression of TSC2 gene. Overexpression of TSC2 exerted the growth inhibitory effect of B88t and HI in vitro and in vivo. These findings suggest that overexpression of TSC2 may exert the antitumor effect on oral cancer cells whether they have high expression of p27Kip1 protein or not.

Mutation analysis of the TSC1 and TSC2 genes in Japanese patients with pulmonary lymphangioleiomyomatosis

Pulmonary lymphangioleiomyomatosis (LAM) is a destructive lung disease characterized by a diffuse hamartomatous proliferation of smooth muscle cells (LAM cells) in the lungs. Pulmonary LAM can occur as an isolated form (sporadic LAM) or in association with tuberous sclerosis complex (TSC) (TSC-LAM), a genetic disorder with autosomal dominant inheritance with various expressivity resulting from mutations of either the TSC1 or TSC2 gene. We examined mutations of both TSC genes in 6 Japanese patients with TSC-LAM and 22 patients with sporadic LAM and identified six unique and novel mutations. TSC2 germline mutations were detected in 2 (33.3%) of 6 patients with TSC-LAM and TSC1 germline mutation in 1 (4.5%) of 22 sporadic LAM patients. In accordance with the tumor-suppressor model, loss of heterozygosity (LOH) was detected in LAM cells from 3 of 4 patients with TSC-LAM and from 4 of 8 patients with sporadic LAM. Furthermore, an identical LOH or two identical somatic mutations were demonstrated in LAM cells microdissected from several tissues, suggesting LAM cells can spread from one lesion to another. Our results from Japanese patients with LAM confirmed the current concept of pathogenesis of LAM: TSC-LAM has a germline mutation but sporadic LAM does not; sporadic LAM is a TSC2 disease with two somatic mutations; and a variety of TSC mutations causes LAM. However, our study indicates that a fraction of sporadic LAM can be a TSC1 disease; therefore, both TSC genes should be examined, even for patients with sporadic LAM.