1
|
De Meulemeester AS, Heylen L, Siekierska A, Mills JD, Romagnolo A, Van Der Wel NN, Aronica E, de Witte PAM. Hyperactivation of mTORC1 in a double hit mutant zebrafish model of tuberous sclerosis complex causes increased seizure susceptibility and neurodevelopmental abnormalities. Front Cell Dev Biol 2022; 10:952832. [PMID: 36238691 PMCID: PMC9552079 DOI: 10.3389/fcell.2022.952832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 09/05/2022] [Indexed: 11/16/2022] Open
Abstract
Tuberous sclerosis complex (TSC) is a multisystem genetic disorder caused by pathogenic variants in TSC1 and TSC2 genes. TSC patients present with seizures and brain abnormalities such as tubers and subependymal giant cells astrocytoma (SEGA). Despite common molecular and clinical features, the severity of the disease varies greatly, even intrafamilially. The second hit hypothesis suggests that an additional, inactivating mutation in the remaining functional allele causes a more severe phenotype and therefore explains the phenotypic variability. Recently, second hit mutations have been detected frequently in mTORopathies. To investigate the pathophysiological effects of second hit mutations, several mouse models have been developed. Here, we opted for a double mutant zebrafish model that carries a LOF mutation both in the tsc2 and the depdc5 gene. To the best of our knowledge, this is the first time a second-hit model has been studied in zebrafish. Significantly, the DEP domain-containing protein 5 (DEPDC5) gene has an important role in the regulation of mTORC1, and the combination of a germline TSC2 and somatic DEPDC5 mutation has been described in a TSC patient with intractable epilepsy. Our depdc5−/−x tsc2−/− double mutant zebrafish line displayed greatly increased levels of mammalian target of rapamycin (mTORC1) activity, augmented seizure susceptibility, and early lethality which could be rescued by rapamycin. Histological analysis of the brain revealed ventricular dilatation in the tsc2 and double homozygotes. RNA-sequencing showed a linear relation between the number of differentially expressed genes (DEGs) and the degree of mTORC1 hyperactivity. Enrichment analysis of their transcriptomes revealed that many genes associated with neurological developmental processes were downregulated and mitochondrial genes were upregulated. In particular, the transcriptome of human SEGA lesions overlapped strongly with the double homozygous zebrafish larvae. The data highlight the clinical relevance of the depdc5−/− x tsc2−/− double mutant zebrafish larvae that showed a more severe phenotype compared to the single mutants. Finally, analysis of gene-drug interactions identified interesting pharmacological targets for SEGA, underscoring the value of our small zebrafish vertebrate model for future drug discovery efforts.
Collapse
Affiliation(s)
| | - Lise Heylen
- Laboratory for Molecular Biodiscovery, KU Leuven, Leuven, Belgium
| | | | - James D. Mills
- Department of (Neuro)Pathology Amsterdam Neuroscience, Amsterdam UMC Location University of Amsterdam, Amsterdam, Netherlands
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, United Kingdom
- Chalfont Centre for Epilepsy, Chalfont St Peter, United Kingdom
| | - Alessia Romagnolo
- Department of (Neuro)Pathology Amsterdam Neuroscience, Amsterdam UMC Location University of Amsterdam, Amsterdam, Netherlands
| | - Nicole N. Van Der Wel
- Department of Medical Biology, Electron Microscopy Center Amsterdam, Amsterdam UMC Location University of Amsterdam, Amsterdam, Netherlands
| | - Eleonora Aronica
- Department of (Neuro)Pathology Amsterdam Neuroscience, Amsterdam UMC Location University of Amsterdam, Amsterdam, Netherlands
- Stichting Epilepsie Instelling Nederland (SEIN), Heemstede, Netherlands
| | - Peter A. M. de Witte
- Laboratory for Molecular Biodiscovery, KU Leuven, Leuven, Belgium
- *Correspondence: Peter A. M. de Witte,
| |
Collapse
|
2
|
Zordan P, Cominelli M, Cascino F, Tratta E, Poliani PL, Galli R. Tuberous sclerosis complex-associated CNS abnormalities depend on hyperactivation of mTORC1 and Akt. J Clin Invest 2018; 128:1688-1706. [PMID: 29389670 DOI: 10.1172/jci96342] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 01/30/2018] [Indexed: 12/11/2022] Open
Abstract
Tuberous sclerosis complex (TSC) is a dominantly inherited disease caused by hyperactivation of the mTORC1 pathway and characterized by the development of hamartomas and benign tumors, including in the brain. Among the neurological manifestations associated with TSC, the tumor progression of static subependymal nodules (SENs) into subependymal giant cell astrocytomas (SEGAs) is one of the major causes of morbidity and shortened life expectancy. To date, mouse modeling has failed in reproducing these 2 lesions. Here we report that simultaneous hyperactivation of mTORC1 and Akt pathways by codeletion of Tsc1 and Pten, selectively in postnatal neural stem cells (pNSCs), is required for the formation of bona fide SENs and SEGAs. Notably, both lesions closely recapitulate the pathognomonic morphological and molecular features of the corresponding human abnormalities. The establishment of long-term expanding pNSC lines from mouse SENs and SEGAs made possible the identification of mTORC2 as one of the mediators conferring tumorigenic potential to SEGA pNSCs. Notably, in spite of concurrent Akt hyperactivation in mouse brain lesions, single mTOR inhibition by rapamycin was sufficient to strongly impair mouse SEGA growth. This study provides evidence that, concomitant with mTORC1 hyperactivation, sustained activation of Akt and mTORC2 in pNSCs is a mandatory step for the induction of SENs and SEGAs, and, at the same time, makes available an unprecedented NSC-based in vivo/in vitro model to be exploited for identifying actionable targets in TSC.
Collapse
Affiliation(s)
- Paola Zordan
- Neural Stem Cell Biology Unit, Division of Regenerative Medicine, Stem Cells and Gene Therapy, San Raffaele Scientific Institute, Milan, Italy
| | - Manuela Cominelli
- Pathology Unit, Molecular and Translational Medicine Department, University of Brescia, Brescia, Italy
| | - Federica Cascino
- Neural Stem Cell Biology Unit, Division of Regenerative Medicine, Stem Cells and Gene Therapy, San Raffaele Scientific Institute, Milan, Italy
| | - Elisa Tratta
- Pathology Unit, Molecular and Translational Medicine Department, University of Brescia, Brescia, Italy
| | - Pietro L Poliani
- Pathology Unit, Molecular and Translational Medicine Department, University of Brescia, Brescia, Italy
| | - Rossella Galli
- Neural Stem Cell Biology Unit, Division of Regenerative Medicine, Stem Cells and Gene Therapy, San Raffaele Scientific Institute, Milan, Italy
| |
Collapse
|
3
|
Bongaarts A, Giannikou K, Reinten RJ, Anink JJ, Mills JD, Jansen FE, Spliet GW, den Dunnen WF, Coras R, Blümcke I, Paulus W, Scholl T, Feucht M, Kotulska K, Jozwiak S, Buccoliero AM, Caporalini C, Giordano F, Genitori L, Söylemezoğlu F, Pimentel J, Nellist M, Schouten-van Meeteren AY, Nag A, Mühlebner A, Kwiatkowski DJ, Aronica E. Subependymal giant cell astrocytomas in Tuberous Sclerosis Complex have consistent TSC1/TSC2 biallelic inactivation, and no BRAF mutations. Oncotarget 2017; 8:95516-95529. [PMID: 29221145 PMCID: PMC5707039 DOI: 10.18632/oncotarget.20764] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 07/31/2017] [Indexed: 12/12/2022] Open
Abstract
Subependymal giant cell astrocytomas (SEGAs) are rare, low-grade glioneuronal brain tumors that occur almost exclusively in patients with tuberous sclerosis complex (TSC). Though histologically benign, SEGAs can lead to serious neurological complications, including hydrocephalus, intractable seizures and death. Previous studies in a limited number of SEGAs have provided evidence for a biallelic two-hit inactivation of either TSC1 or TSC2, resulting in constitutive activation of the mechanistic target of rapamycin complex 1 pathway. The activating BRAF V600E mutation is a common genetic alteration in low grade gliomas and glioneuronal tumors, and has been reported in SEGAs as well. In the present study, we assessed the prevalence of the BRAF V600E mutation in a large cohort of TSC related SEGAs (n=58 patients including 56 with clinical TSC) and found no evidence of either BRAF V600E or other mutations in BRAF. To confirm that these SEGAs fit the classic model of two hit TSC1 or TSC2 inactivation, we also performed massively parallel sequencing of these loci. Nineteen (19) of 34 (56%) samples had mutations in TSC2, 10 (29%) had mutations in TSC1, while 5 (15%) had no mutation identified in TSC1/TSC2. The majority of these samples had loss of heterozygosity in the same gene in which the mutation was identified. These results significantly extend previous studies, and in agreement with the Knudson two hit mechanism indicate that biallelic alterations in TSC2 and less commonly, TSC1 are consistently seen in SEGAs.
Collapse
Affiliation(s)
- Anika Bongaarts
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Krinio Giannikou
- Division of Pulmonary and Critical Care Medicine and of Genetics, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Roy J. Reinten
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Jasper J. Anink
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - James D. Mills
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Floor E. Jansen
- Department of Pediatric Neurology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - G.M Wim Spliet
- Department of Pathology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Willfred F.A. den Dunnen
- Department of Pathology and Medical Biology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Roland Coras
- Department of Neuropathology, University Hospital Erlangen, Erlangen, Germany
| | - Ingmar Blümcke
- Department of Neuropathology, University Hospital Erlangen, Erlangen, Germany
| | - Werner Paulus
- Institute of Neuropathology, University Hospital Münster, Münster, Germany
| | - Theresa Scholl
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
| | - Martha Feucht
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
| | - Katarzyna Kotulska
- Department of Neurology and Epileptology, Children's Memorial Health Institute, Warsaw, Poland
| | - Sergiusz Jozwiak
- Department of Child Neurology, Medical University of Warsaw, Warsaw, Poland
| | | | | | - Flavio Giordano
- Department of Neurosurgery, Anna Meyer Children's Hospital, Florence, Italy
| | - Lorenzo Genitori
- Department of Neurosurgery, Anna Meyer Children's Hospital, Florence, Italy
| | - Figen Söylemezoğlu
- Department of Pathology, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - José Pimentel
- Department of Neurology, Hospital de Santa Maria, Lisbon, Portugal
| | - Mark Nellist
- Department of Clinical Genetics, Erasmus Medical Centre, Rotterdam, The Netherlands
| | | | - Anwesha Nag
- Center for Cancer Genome Discovery, Dana Farber Cancer Institute, Boston, Massachusetts, USA
| | - Angelika Mühlebner
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
| | - David J. Kwiatkowski
- Division of Pulmonary and Critical Care Medicine and of Genetics, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Eleonora Aronica
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
- Stichting Epilepsie Instellingen Nederland (SEIN), The Netherlands
- Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, Amsterdam, The Netherlands
| |
Collapse
|
4
|
Patil VV, Guzman M, Carter AN, Rathore G, Yoshor D, Curry D, Wilfong A, Agadi S, Swann JW, Adesina AM, Bhattacharjee MB, Anderson AE. Activation of extracellular regulated kinase and mechanistic target of rapamycin pathway in focal cortical dysplasia. Neuropathology 2015; 36:146-56. [PMID: 26381727 DOI: 10.1111/neup.12242] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 07/31/2015] [Accepted: 08/01/2015] [Indexed: 12/26/2022]
Abstract
Neuropathology of resected brain tissue has revealed an association of focal cortical dysplasia (FCD) with drug-resistant epilepsy (DRE). Recent studies have shown that the mechanistic target of rapamycin (mTOR) pathway is hyperactivated in FCD as evidenced by increased phosphorylation of the ribosomal protein S6 (S6) at serine 240/244 (S(240/244) ), a downstream target of mTOR. Moreover, extracellular regulated kinase (ERK) has been shown to phosphorylate S6 at serine 235/236 (S(235/236) ) and tuberous sclerosis complex 2 (TSC2) at serine 664 (S(664) ) leading to hyperactive mTOR signaling. We evaluated ERK phosphorylation of S6 and TSC2 in two types of FCD (FCD I and FCD II) as a candidate mechanism contributing to mTOR pathway dysregulation. Tissue samples from patients with tuberous sclerosis (TS) served as a positive control. Immunostaining for phospho-S6 (pS6(240/244) and pS6(235/236) ), phospho-ERK (pERK), and phospho-TSC2 (pTSC2) was performed on resected brain tissue with FCD and TS. We found increased pS6(240/244) and pS6(235/236) staining in FCD I, FCD II and TS compared to normal-appearing tissue, while pERK and pTSC2 staining was increased only in FCD IIb and TS tissue. Our results suggest that both the ERK and mTOR pathways are dysregulated in FCD and TS; however, the signaling alterations are different for FCD I as compared to FCD II and TS.
Collapse
Affiliation(s)
- Vinit V Patil
- Program in Translational Biology and Molecular Medicine, Texas Children's Hospital, Houston, Texas, USA.,Cain Foundation Laboratories, Texas Children's Hospital, Houston, Texas, USA.,Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas, USA.,Department of Pathology, Saint Louis University, Saint Louis, Missouri
| | - Miguel Guzman
- Department of Pathology, Saint Louis University, Saint Louis, Missouri
| | - Angela N Carter
- Department of Neuroscience, Texas Children's Hospital, Houston, Texas, USA.,Cain Foundation Laboratories, Texas Children's Hospital, Houston, Texas, USA.,Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas, USA
| | - Geetanjali Rathore
- Department of Pediatrics, Texas Children's Hospital, Houston, Texas, USA
| | - Daniel Yoshor
- Department of Neurosurgery, Texas Children's Hospital, Houston, Texas, USA
| | - Daniel Curry
- Department of Neurosurgery, Texas Children's Hospital, Houston, Texas, USA
| | - Angus Wilfong
- Department of Neurology, Texas Children's Hospital, Houston, Texas, USA.,Department of Pediatrics, Texas Children's Hospital, Houston, Texas, USA
| | - Satish Agadi
- Department of Neurology, Texas Children's Hospital, Houston, Texas, USA.,Department of Pediatrics, Texas Children's Hospital, Houston, Texas, USA
| | - John W Swann
- Department of Neuroscience, Texas Children's Hospital, Houston, Texas, USA.,Department of Pediatrics, Texas Children's Hospital, Houston, Texas, USA.,Program in Translational Biology and Molecular Medicine, Texas Children's Hospital, Houston, Texas, USA.,Cain Foundation Laboratories, Texas Children's Hospital, Houston, Texas, USA.,Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas, USA
| | | | - Meenakshi B Bhattacharjee
- Department of Pathology and Laboratory Medicine, University of Texas Medical School, Houston, Texas, USA
| | - Anne E Anderson
- Department of Neurology, Texas Children's Hospital, Houston, Texas, USA.,Department of Neuroscience, Texas Children's Hospital, Houston, Texas, USA.,Department of Pediatrics, Texas Children's Hospital, Houston, Texas, USA.,Program in Translational Biology and Molecular Medicine, Texas Children's Hospital, Houston, Texas, USA.,Cain Foundation Laboratories, Texas Children's Hospital, Houston, Texas, USA.,Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas, USA
| |
Collapse
|
5
|
Ouyang T, Zhang N, Benjamin T, Wang L, Jiao J, Zhao Y, Chen J. Subependymal giant cell astrocytoma: current concepts, management, and future directions. Childs Nerv Syst 2014; 30:561-70. [PMID: 24549759 DOI: 10.1007/s00381-014-2383-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2013] [Accepted: 02/06/2014] [Indexed: 12/16/2022]
Abstract
BACKGROUND Subependymal giant cell astrocytoma (SEGA) is the most common central nervous system tumor in patients with tuberous sclerosis complex (TSC). SEGAs are generally benign, non-infiltrative lesions, but they can lead to intracranial hypertension, obstructive hydrocephalus, focal neurologic deficits, and even sudden death. DISCUSSION Surgical resection has been the standard treatment for SEGAs, and it is generally curative with complete resection. However, not all SEGAs are amenable to safe and complete resection. Gamma Knife stereotactic radiosurgery provides another treatment option as a primary or adjuvant treatment for SEGAs, but it has highly variable response effects with sporadic cases demonstrating its efficacy. Recently, biologically targeted pharmacotherapy with mammalian target of rapamycin (mTOR) inhibitors such as sirolimus and everolimus has provided a safe and efficacious treatment option for patients with SEGAs. However, SEGAs can recur few months after drug discontinuation, indicating that mTOR inhibitors may need to be continued to avoid recurrence. Further studies are needed to evaluate the advantages and adverse effects of long-term treatment with mTOR inhibitors. This review presents an overview of the current knowledge and particularly highlights the surgical and medical options of SEGAs in patients with TSC.
Collapse
Affiliation(s)
- Taohui Ouyang
- Department of Neurosurgery, Tongji Hospital, Huazhong University of Science and Technology, Wuhan, 430030, China
| | | | | | | | | | | | | |
Collapse
|
6
|
Tyburczy ME, Kotulska K, Pokarowski P, Mieczkowski J, Kucharska J, Grajkowska W, Roszkowski M, Jozwiak S, Kaminska B. Novel proteins regulated by mTOR in subependymal giant cell astrocytomas of patients with tuberous sclerosis complex and new therapeutic implications. THE AMERICAN JOURNAL OF PATHOLOGY 2010; 176:1878-90. [PMID: 20133820 DOI: 10.2353/ajpath.2010.090950] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Subependymal giant cell astrocytomas (SEGAs) are rare brain tumors associated with tuberous sclerosis complex (TSC), a disease caused by mutations in TSC1 or TSC2, resulting in enhancement of mammalian target of rapamycin (mTOR) activity, dysregulation of cell growth, and tumorigenesis. Signaling via mTOR plays a role in multifaceted genomic responses, but its effectors in the brain are largely unknown. Therefore, gene expression profiling on four SEGAs was performed with Affymetrix Human Genome arrays. Of the genes differentially expressed in TSC, 11 were validated by real-time PCR on independent tumor samples and 3 SEGA-derived cultures. Expression of several proteins was confirmed by immunohistochemistry. The differentially-regulated proteins were mainly involved in tumorigenesis and nervous system development. ANXA1, GPNMB, LTF, RND3, S100A11, SFRP4, and NPTX1 genes were likely to be mTOR effector genes in SEGA, as their expression was modulated by an mTOR inhibitor, rapamycin, in SEGA-derived cells. Inhibition of mTOR signaling affected size of cultured SEGA cells but had no influence on their proliferation, morphology, or migration, whereas inhibition of both mTOR and extracellular signal-regulated kinase signaling pathways led to significant alterations of these processes. For the first time, we identified genes related to the occurrence of SEGA and regulated by mTOR and demonstrated an effective modulation of SEGA growth by pharmacological inhibition of both mTOR and extracellular signal-regulated kinase signaling pathways, which could represent a novel therapeutic approach.
Collapse
|
7
|
Jozwiak J, Sahin M, Jozwiak S, Kotulska K, Ploski R, Szperl M, Wlodarski PK. Cardiac rhabdomyoma in tuberous sclerosis: Hyperactive Erk signaling. Int J Cardiol 2009; 132:145-7. [DOI: 10.1016/j.ijcard.2007.07.152] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2007] [Accepted: 07/07/2007] [Indexed: 10/22/2022]
|
8
|
Fibroblasts From Normal Skin of a Tuberous Sclerosis Patient Show Upregulation of mTOR Pathway. Am J Dermatopathol 2009; 31:68-70. [DOI: 10.1097/dad.0b013e3181882c09] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
9
|
Baskin HJ. The pathogenesis and imaging of the tuberous sclerosis complex. Pediatr Radiol 2008; 38:936-52. [PMID: 18414839 DOI: 10.1007/s00247-008-0832-y] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Revised: 03/03/2008] [Accepted: 03/12/2008] [Indexed: 01/08/2023]
Abstract
Tuberous sclerosis complex (TSC) is an autosomal-dominant disorder characterized by the formation of hamartomatous lesions in multiple organ systems. It is the second most common neurocutaneous syndrome after neurofibromatosis type 1 and has been recognized since the late 1800s. Although the disease has complete penetrance, there is also high phenotypic variability: some patients have obvious signs at birth, while others remain undiagnosed for many years. In addition to skin lesions, TSC patients develop numerous brain lesions, angiomyolipoma (AMLs), lymphangiomyomatosis (LAM) in the lungs, cardiac rhabdomyomas, skeletal lesions, and vascular anomalies, all of which are well seen with medical imaging. Our knowledge of TSC genetics and pathophysiology has expanded dramatically in recent years: two genetic loci were discovered in the 1990s and recent elucidation of TSC's interaction with the mTOR pathway has changed how we manage the disease. Meanwhile, medical imaging is playing an increasingly important role in the diagnosis, management, and treatment of TSC. We provide an update on the genetics and pathophysiology of TSC, review its clinical manifestations, and explore the breadth of imaging features in each organ system, from prenatal detection of cardiac rhabdomyomas to monitoring rapamycin therapy to treatment of AMLs by interventional radiology.
Collapse
Affiliation(s)
- Henry J Baskin
- Department of Radiology, Cincinnati Children's Medical Center, 333 Burnet Ave., Cincinnati, OH 45229, USA.
| |
Collapse
|
10
|
Abstract
Tuberous sclerosis (TS), neurocutaneous disorder resulting from the mutation of 1 of 2 genes, TSC1 or TSC2, is often associated with the formation of hamartomatous lesions in various organ systems, including the skin. TS patients may present with hypomelanic macules, confetti-like spots, facial angiofibromas, ungual fibromas, shagreen patches, forehead plaques, and other dermatological signs. Some of these manifestations are pathognomic for TS and thus should be carefully evaluated when TS diagnosis is suspected. Little is known however on molecular links connecting disease pathogenesis and formation of such hamartomas. In the current review, we describe molecular pathways thought to be responsible for the development of the disease and show how their upregulation may affect the skin. Special attention is paid to protein kinase B (PKB/Akt), extracellular signal-regulated kinase, and mammalian target of rapamycin, which have recently been found to participate in the control of melanin biosynthesis through microphthalmia-associated transcription factor and tyrosinase transcription.
Collapse
|
11
|
Abstract
The two-hit hypothesis presented by Knudson in 1971 explains the development of tumours deficient in anti-oncogenes. Hamartomas in patients with tuberous sclerosis usually fit into this model, the first hit is a congenital lesion of either of the tuberous sclerosis genes (TSC1 or TSC2), and the second hit is loss of heterozygosity of this gene. Although this mechanism is true for most tumours associated with tuberous sclerosis, only 30-60% of brain and cardiac tumours show loss of heterozygosity--the remaining tumours develop despite the presence of an intact allele. Tumours in which loss of heterozygosity is rare, such as subependymal giant-cell astrocytoma, might all share a common feature that mimics loss of heterozygosity either by inactivation of the TSC complex or by direct activation of mammalian target of rapamycin (mTOR) or its downstream targets. Because phosphorylation of the TSC complex can inactivate it, expression and activation patterns of protein kinase B (AKT) and extracellular signal-regulated kinase (ERK), two potent protein kinases that are activators of the mTOR pathway, have been implicated. AKT activation is detected only in few samples, whereas ERK is hyperactive in all subependymal giant-cell astrocytomas. We postulate that ERK activation consistently detected in different tuberous-sclerosis-associated tumours is a molecular trigger for the development of these neoplasms.
Collapse
Affiliation(s)
- Jaroslaw Jozwiak
- Department of Histology and Embryology, Center for Biostructure Research, Medical University of Warsaw, Warsaw, Poland.
| | | | | |
Collapse
|