Survey of somatic mutations in tuberous sclerosis complex (TSC) hamartomas suggests different genetic mechanisms for pathogenesis of TSC lesions.
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ABSTRACT:
SUBMITTER: Niida Y
PROVIDER: S-EPMC1235480 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Tuberous sclerosis complex (TSC) is a model disorder for understanding brain development because the genes that cause TSC are known, many downstream molecular pathways have been identified, and the resulting perturbations of cellular events are established. TSC, therefore, provides an intellectual framework to understand the molecular and biochemical pathways that orchestrate normal brain development. The TSC1 and TSC2 genes encode Hamartin and Tuberin which form a GTPase activating protein (GAP) complex. Inactivating mutations in TSC genes (TSC1/TSC2) cause sustained Ras homologue enriched in brain (RHEB) activation of the mammalian isoform of the target of rapamycin complex 1 (mTORC1). TOR is a protein kinase that regulates cell size in many organisms throughout nature. mTORC1 inhibits catabolic processes including autophagy and activates anabolic processes including mRNA translation. mTORC1 regulation is achieved through two main upstream mechanisms. The first mechanism is regulation by growth factor signaling. The second mechanism is regulation by amino acids. Gene mutations that cause too much or too little mTORC1 activity lead to a spectrum of neuroanatomical changes ranging from altered brain size (micro and macrocephaly) to cortical malformations to Type I neoplasias. Because somatic mutations often underlie these changes, the timing, and location of mutation results in focal brain malformations. These mutations, therefore, provide gain-of-function and loss-of-function changes that are a powerful tool to assess the events that have gone awry during development and to determine their functional physiological consequences. Knowledge about the TSC-mTORC1 pathway has allowed scientists to predict which upstream and downstream mutations should cause commensurate neuroanatomical changes. Indeed, many of these predictions have now been clinically validated. A description of clinical imaging and histochemical findings is provided in relation to laboratory models of TSC that will allow the reader to appreciate how human pathology can provide an understanding of the fundamental mechanisms of development.
| S-EPMC7381175 | biostudies-literature
Project description:Patients with tuberous sclerosis complex (TSC) develop hamartomas containing biallelic inactivating mutations in either TSC1 or TSC2, resulting in mammalian target of rapamycin (mTOR) activation. Hamartomas overgrow epithelial and mesenchymal cells in TSC skin. The pathogenetic mechanisms for these changes had not been investigated, and the existence or location of cells with biallelic mutations ("two-hit" cells) was unclear. We compared TSC skin hamartomas (angiofibromas and periungual fibromas) with normal-appearing skin of the same patient, and we observed more proliferation and mTOR activation in hamartoma epidermis. Two-hit cells were not detected in the epidermis. Fibroblast-like cells in the dermis, however, exhibited allelic deletion of TSC2, in both touch preparations of fresh tumor samples and cells grown from TSC skin tumors, suggesting that increased epidermal proliferation and mTOR activation were not caused by second-hit mutations in the keratinocytes but by mesenchymal-epithelial interactions. Gene expression arrays, used to identify potential paracrine factors released by mesenchymal cells, revealed more epiregulin mRNA in fibroblast-like angiofibroma and periungual fibroma cells than in fibroblasts from normal-appearing skin of the same patient. Elevation of epiregulin mRNA was confirmed with real-time PCR, and increased amounts of epiregulin protein were demonstrated with immunoprecipitation. Epiregulin stimulated keratinocyte proliferation and phosphorylation of ribosomal protein S6 in vitro. These results suggest that hamartomatous TSC skin tumors are induced by paracrine factors released by two-hit cells in the dermis and that proliferation with mTOR activation of the overlying epidermis is an effect of epiregulin.
| S-EPMC2265180 | biostudies-literature
Project description:BackgroundA pivotal developmental question is whether tubers in tuberous sclerosis complex (TSC) form by germline and somatic TSC1 or TSC2 gene mutations. Loss of TSC1 or TSC2 in vitro and in vivo leads to mTORC1 cascade activation and ribosomal protein S6 phosphorylation (P-S6). Giant cells (GCs) in tubers exhibit S6 phosphorylation, suggesting cell-specific loss of TSC gene function.MethodsTSC1 and TSC2 gene mutations were investigated in DNA extracted from tuber sections (n = 6) and microdissected P-S6-labeled GCs by sequencing and loss of heterozygosity (LOH) analysis to define germline and somatic mutations.ResultsA germline TSC1 mutation was defined in 1 case and TSC2 mutations were defined in 5 cases. LOH was not detected in whole tuber sections or microdissected P-S6-labeled GCs. TSC1 and TSC2 were sequenced in microdissected P-S6-immunolabeled GCs. In 5 specimens, a somatic mutation was identified in single GCs that was not detected in whole tuber sections or leukocyte DNA. Four somatic mutations were novel variants (1 nonsense and 3 missense mutations) and 1 additional nonsense somatic mutation was previously reported as a germline mutation. In 1 case, no somatic mutation was identified. There was reduced expression of TSC1 or TSC2 transcripts in the TSC1 or TSC2 associated specimens. In the cases containing a nonsense mutation, no transcript mRNA was detected, suggesting nonsense-mediated degradation.ConclusionsWe provide evidence to support the hypothesis that tubers form by biallelic TSC1 or TSC2 gene inactivation reflecting a "2-hit" mechanism of germline and somatic mutational events. AML = angiomyolipoma; DN = dysplastic neuron; FFPE = formalin fixed, paraffin embedded; GC = giant cell; H-E = hematoxylin and eosin; LOH = loss of heterozygosity; TSC = tuberous sclerosis complex.
| S-EPMC2882213 | biostudies-literature
Project description:Chordoma associated with tuberous sclerosis complex (TSC) are an extremely rare tumor that was described only in 13 cases since 1975. Сhordomas themselves are malignant slow-growing bone tumors thought to arise from vestigial or ectopic notochordal tissue. In total, with CMA we found 180 regions with CNVs in the chordoma tumor sample. The longest section was 58,014 kbp long (arr[GRCh38] 9q21.31q34.3(79267492_137281464)x1-2), harboring region 9q34 that includes TSC1 gene. Also, 12 oncogenes including KRAS and CBX7 were in amplified regions and 92 tumor suppressor genes were in regions with loss status. Four genes that participate in epigenetic regulation, - ELP3, GTF3C4, MBD2, and PHF2 were found to be affected. Moreover, members of the APOBEC3 family were amplified.
2022-02-16 | GSE196823 | GEO
Project description:We sought to explore the relationship between renal lesion features and genetic mutations in tuberous sclerosis complex (TSC) patients. TSC patients with renal lesions were subjected to TSC1/2 gene next-generation sequencing (NGS). TSC1/2 mutation types and imaging examinations were screened for combined analysis of genetic and clinical features. Seventy-three probands among TSC patients with renal lesions were included. Twenty affected relatives were also included. In total, 93 patients were included. Eighty patients (86.0%) had bilateral renal angiomyolipomas (AMLs), and one had epithelioid AML. Two patients had polycystic kidney disease, one had renal cell carcinoma, and one had Wilms tumor. Among the 73 probands, four had TSC1 mutations, 53 had TSC2 mutations, and 16 had no mutations identified (NMI). There was no statistically significant difference between TSC1 mutation, TSC2 mutation and NMI group (P= 0.309), or between familial and sporadic groups (P= 0.775) when considering AML size. There was no statistically significant difference between pathogenic/likely pathogenic and benign/likely benign/NMI groups (P= 0.363) or among patients with different mutation types of TSC2 (P= 0.906). The relationship between the conditions of TSC gene mutations and the severity of renal lesions still needs more analysis. Patients with NMI, particularly those with familial disease, need more attention because the pathogenesis remains unknown.
| S-EPMC9152844 | biostudies-literature
Project description:Individuals with comorbidities are at higher risk of coronavirus disease 2019 (COVID-19) and worse outcome, but little information has been available about patients with genetic diseases and COVID-19. This study aims at evaluating the presence and outcome of COVID-19 in a cohort of Italian patients with tuberous sclerosis complex (TSC) and/or lymphangioleiomyomatosis (LAM), and at reviewing the possible effects of mTOR inhibitors on SARS-CoV-2 infection. We included 102 unselected individuals with a diagnosis of TSC and/or LAM assessed between January 1, 2020 and April 24, 2020 (29% children, 71% adults). Twenty-six patients were on mTOR inhibitors. Demographic data, TSC manifestations, presence, and outcomes in individuals with confirmed or suspected SARS-CoV-2 infection were evaluated. Health status and outcomes of all patients on mTOR inhibitors were assessed. One patient with severe TSC had polymerase chain reaction (PCR)-confirmed SARS-CoV-2 infection, was admitted to ICU, and died. Nine additional patients either met the definition of suspect case or presented with at least two of the most common symptoms of SARS-CoV-2 infection. All recovered fully. None of the patients treated with mTOR inhibitors for their underlying comorbidities was diagnosed with COVID-19, and those who showed suspicious respiratory symptoms recovered fully. This cohort study provides preliminary information on COVID-19 in people with TSC in Italy and suggests feasibility to systematically evaluate the role of mTOR inhibitors in SARS-CoV-2 infection.
| S-EPMC7461282 | biostudies-literature
Project description:Tuberous sclerosis complex (TSC) is a monogenetic disease that arises due to mutations in either the TSC1 or TSC2 gene and affects multiple organ systems. One of the hallmark manifestations of TSC are cortical malformations referred to as cortical tubers. These tubers are frequently associated with treatment-resistant epilepsy. Some of these patients are candidates for epilepsy surgery. White matter abnormalities, such as loss of myelin and oligodendroglia, have been described in a small subset of resected tubers but mechanisms underlying this phenomenon are unclear. Herein, we analyzed a variety of neuropathologic and immunohistochemical features in gray and white matter areas of resected cortical tubers from 46 TSC patients using semi-automated quantitative image analysis. We observed divergent amounts of myelin basic protein as well as numbers of oligodendroglia in both gray and white matter when compared with matched controls. Analyses of clinical data indicated that reduced numbers of oligodendroglia were associated with lower numbers on the intelligence quotient scale and that lower amounts of myelin-associated oligodendrocyte basic protein were associated with the presence of autism-spectrum disorder. In conclusion, myelin pathology in cortical tubers extends beyond the white matter and may be linked to cognitive dysfunction in TSC patients.
| S-EPMC7559237 | biostudies-literature
Project description:ContextTuberous sclerosis complex (TSC) is a genetic disease in the group known as neurocutaneous syndromes, with dominant autosomal inheritance. It is characterized by skin and adnexal lesions and central and peripheral nervous system tumors, with neurological and psychiatric findings. It may affect the heart, kidneys, eyes, face, bones, lungs, stomach and dentition.Case reportWe present the case of a 66-year-old man with dermatological signs that included hypopigmented maculae, confetti-like lesions, shagreen plaque, angiofibromas on nasolabial folds, neck and back, nail dystrophy and periungual fibromas on fingers and toes. An electroencephalogram produced normal results, but magnetic resonance imaging showed a nodular image measuring 1.2 x 1.0 cm close to the Monro foramen, which was similar to cerebral parenchyma and compatible with a subependymal giant-cell astrocytoma. A conservative approach was taken, through control imaging examinations on the lesion for seven years, with absence of any expansive process or neurological symptoms. Abdominal ultrasonography revealed a solid, heterogenic and echogenic mass with a calcified focus, measuring 4.6 x 3.4 cm, in the rightkidney, compatible with angiomyolipoma. The patient was treated by means of complete nephrectomy because of malignant areas seen on histopathological examination and died one month after the procedure. This case report illustrates the importance of oral clinical findings such as dental enamel pits and angiofibromas in making an early diagnosis of TSC, with subsequent screening examinations, treatment and genetic counseling.
| S-EPMC10876329 | biostudies-literature
Project description:In tuberous sclerosis complex (TSC), overexpression of numerous genes associated with inflammation has been observed. Among different proinflammatory cytokines, interleukin-1β (IL-1β) has been shown to be significantly involved in epileptogenesis and maintenance of seizures. Recent evidence indicates that IL-1β gene expression can be regulated by DNA methylation of its promoter. In the present study, we hypothesized that hypomethylation in the promoter region of the IL-1β gene may underlie its overexpression observed in TSC brain tissue. Bisulfite sequencing was used to study the methylation status of the promoter region of the IL-1β gene in TSC and control samples. We identified hypomethylation in the promoter region of the IL-1β gene in TSC samples. IL-1β is overexpressed in tubers, and gene expression is correlated with promoter hypomethylation at CpG and non-CpG sites. Our results provide the first evidence of epigenetic modulation of the IL-1β signaling in TSC. Thus, strategies that target epigenetic alterations could offer new therapeutic avenues to control the persistent activation of interleukin-1β-mediated inflammatory signaling in TSC brain.
| S-EPMC4972849 | biostudies-literature
Project description:BackgroundTuberous sclerosis complex (TSC) is an autosomal dominant genetic condition that involves abnormalities of the skin, hamartomas in the heart, brain, and kidneys, seizures, as well as TSC-associated neuropsychiatric disorders (TAND). About 90%-95% of individuals with TSC will have an identifiable pathogenic variant in either TSC1 or TSC2. We present here two family members with clinical diagnoses of TSC that were later determined to be due to two different genetic etiologies.MethodsA 2-year-old Caucasian female (Patient 1) was born to non-consanguineous healthy parents and was determined to have a clinical diagnosis of TSC at 2 months old. Her paternal great-uncle (Patient 2) was also known to have a clinical diagnosis of TSC. Sequencing and deletion/duplication analysis for TSC1 and TSC2 were performed on both individuals.ResultsMutation analysis revealed that both Patient 1 and Patient 2 had identifiable pathogenic variants in TSC2. Patient 1 had c.4800_4801delTG (p.Cys1600Trpfs*2), while Patient 2 had c.4470_4471delinsTT (p.Glu1490_Lys1491delinsAsp*).ConclusionTo our knowledge, our clinical report is of significance as it is the third kindred to be identified with affected members with two distinct genetic etiologies for TSC. Our case report highlights the importance of incorporating genetic testing into the clinical evaluation for individuals with features suggestive of TSC.
| S-EPMC7336739 | biostudies-literature