Comprehensive mutation analysis of TSC1 and TSC2-and phenotypic correlations in 150 families with tuberous sclerosis

Topographical Distribution of Epileptogenic Tubers in Patients With Tuberous Sclerosis Complex

Tuberous sclerosis complex is a multisystem genetic syndrome often affecting the central nervous system. The purpose of the current study was to identify topographical patterns in the distribution specific to epileptogenic (n = 37) and nonepileptogenic (n = 544) tubers throughout the brain for a cohort of 23 tuberous sclerosis complex patients with a history of seizures. Tubers localized to the inferior parietal lobes, middle frontal lobes, middle temporal lobes, or central sulcus regions were associated with a high frequency of epileptogenic tubers. Epileptogenic tubers occurred statistically more frequently within the inferior parietal lobe and within the central sulcus region in children younger than 1 or between 1 and 3 years old, respectively. Results imply seizure activity in tuberous sclerosis complex patients can be associated with the location of cortical tubers.

The clinical profile of tuberous sclerosis complex (TSC) in the United Kingdom: A retrospective cohort study in the Clinical Practice Research Datalink (CPRD)

BACKGROUND

Tuberous Sclerosis Complex (TSC) is a multi-system genetic disorder characterised by the development of benign growths and diverse clinical manifestations, varying in severity, age at onset and with high clinical burden.

AIMS

This longitudinal study aims to describe the broad spectrum of clinical manifestation profiles in a large, representative cohort of TSC patients in the UK in order to better understand disease complexity.

METHODS

TSC patients in the Clinical Practice Research Datalink (CPRD) and linked Hospital Episodes Statistics (CPRD-HES) were retrospectively identified between 1987 and 2013. Available history was extracted for each patient and clinical diagnosis, procedure and medication records reviewed. A random selection of patients from the CPRD-HES was used as a Comparator cohort.

RESULTS

Three hundred and thirty-four TSC patients with a mean (SD) age of 30.3 (18.6) years were identified (53% female). TSC was diagnosed at mean age 3.2 (4.2) years. Epilepsy and psychiatric manifestations were reported frequently in paediatric (77% and 55%, respectively) and adult patients (66% and 68%, respectively). The prevalence of manifestations in the TSC cohort was markedly higher versus the Comparator cohort. The majority of paediatric (46%) and adult TSC patients (62%) developed clinical manifestations affecting at least three organ systems and forty-nine distinctive organ system manifestation profiles were identified.

CONCLUSIONS

TSC patients present with multiple and complex clinical manifestations and profiles that necessitate the co-ordinated action of a multidisciplinary team in order to improve the quality and efficiency of care.

Genotype/Phenotype Correlations in Tuberous Sclerosis Complex

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by the development of widespread hamartomatous lesions in various organs, including brain, skin, kidneys, heart, and eyes. Central nervous system is almost invariably involved, with up to 85% of patients presenting with epilepsy, and at least half of patients having intellectual disability or other neuropsychiatric disorders including autism spectrum disorder. TSC is caused by the mutation in one of the 2 genes TSC1, at 9q34, and TSC2, at 16p13.3. They respectively encode for hamartin and tuberin, which form an intracellular complex inhibiting the mammalian target of rapamycin. Mammalian target of rapamycin overactivation following the genetic defect determines the cell growth and proliferation responsible for TSC-related lesions, as well as the alterations in neuronal excitability and synaptogenesis leading to epilepsy and neuropsychiatric disorders. A causative mutation for the disorder is identified in about 85% of patients with a clinical diagnosis of TSC. Mosaicism and technology limits likely explain most of the no mutation identified cases. This review confirms that patients with TSC2 mutations considered as a group usually present a more severe phenotype, characterized by higher number of tubers, earlier age at seizure onset and higher prevalence of intellectual disability. However, the clinical phenotype of the disease presents a high variability, thus making the prediction of the phenotype on an individual basis still challenging. The increasing application of new molecular techniques to subjects with TSC has the potential to significantly reduce the rate of patients with no mutation demonstrated and to identify an increasing higher number of mutations. This would hopefully allow a better characterization of higher risk mutations, which might help clinicians to plan individualized surveillance plans. Furthermore, the increasing availability of disease registries to collect clinical and genetics data of patients help to define more valid and clinically oriented genotype or phenotype correlations.

Mosaic and Intronic Mutations in TSC1/TSC2 Explain the Majority of TSC Patients with No Mutation Identified by Conventional Testing

Tuberous sclerosis complex (TSC) is an autosomal dominant tumor suppressor gene syndrome due to germline mutations in either TSC1 or TSC2. 10–15% of TSC individuals have no mutation identified (NMI) after thorough conventional molecular diagnostic assessment. 53 TSC subjects who were NMI were studied using next generation sequencing to search for mutations in these genes. Blood/saliva DNA including parental samples were available from all subjects, and skin tumor biopsy DNA was available from six subjects. We identified mutations in 45 of 53 subjects (85%). Mosaicism was observed in the majority (26 of 45, 58%), and intronic mutations were also unusually common, seen in 18 of 45 subjects (40%). Seventeen (38%) mutations were seen at an allele frequency < 5%, five at an allele frequency < 1%, and two were identified in skin tumor biopsies only, and were not seen at appreciable frequency in blood or saliva DNA. These findings illuminate the extent of mosaicism in TSC, indicate the importance of full gene coverage and next generation sequencing for mutation detection, show that analysis of TSC-related tumors can increase the mutation detection rate, indicate that it is not likely that a third TSC gene exists, and enable provision of genetic counseling to the substantial population of TSC individuals who are currently NMI.

Tuberous sclerosis complex (TSC) is a human genetic disorder due to mutations in the TSC1 or TSC2 genes. A mystery for many years has been the fact that with standard genetic testing 10–15% of TSC patients have had no mutation identified (NMI) in either TSC1 or TSC2. We examined the genetic cause of TSC in patients who were ‘NMI’ after previous testing. We found a mutation in TSC1 or TSC2 in the vast majority of the subjects studied: 45 of 53 (85%). The majority of mutations identified were either in introns or mosaic or both. Usually we expect to find mutations causing human disease in exons, coding parts of genes. However, mutations can also be found in introns, the non-coding parts of genes, and we found intronic mutations in 18 of 45 subjects (40%). Mosaic mutations were seen in 26 of 45 subjects (58%). Mosaicism is the situation in which different cells in the body have a different genetic make-up, and in this case the mutations in TSC1/TSC2 were present in only a fraction of the cells from the patient. So these two types of hard-to-find mutations (in introns and/or mosaic) explain the majority of TSC patients who were NMI.

A novel mouse model of tuberous sclerosis complex (TSC): eye-specific Tsc1-ablation disrupts visual-pathway development

Tuberous sclerosis complex (TSC) is an autosomal dominant syndrome that is best characterised by neurodevelopmental deficits and the presence of benign tumours (called hamartomas) in affected organs. This multi-organ disorder results from inactivating point mutations in either the TSC1 or the TSC2 genes and consequent activation of the canonical mammalian target of rapamycin complex 1 signalling (mTORC1) pathway. Because lesions to the eye are central to TSC diagnosis, we report here the generation and characterisation of the first eye-specific TSC mouse model. We demonstrate that conditional ablation of Tsc1 in eye-committed progenitor cells leads to the accelerated differentiation and subsequent ectopic radial migration of retinal ganglion cells. This results in an increase in retinal ganglion cell apoptosis and consequent regionalised axonal loss within the optic nerve and topographical changes to the contra- and ipsilateral input within the dorsal lateral geniculate nucleus. Eyes from adult mice exhibit aberrant retinal architecture and display all the classic neuropathological hallmarks of TSC, including an increase in organ and cell size, ring heterotopias, hamartomas with retinal detachment, and lamination defects. Our results provide the first major insight into the molecular etiology of TSC within the developing eye and demonstrate a pivotal role for Tsc1 in regulating various aspects of visual-pathway development. Our novel mouse model therefore provides a valuable resource for future studies concerning the molecular mechanisms underlying TSC and also as a platform to evaluate new therapeutic approaches for the treatment of this multi-organ disorder.

Editors' choice: Conditional deletion of Tsc1 in the eye results in hamartoma formation and defects in retinal ganglion cell development – a novel mouse model providing insights into visual pathway involvement in TSC.

Left-right asymmetry in the light of TOR: An update on what we know so far

The internal left‐right (LR) asymmetry is a characteristic that exists throughout the animal kingdom from roundworms over flies and fish to mammals. Cilia, which are antenna‐like structures protruding into the extracellular space, are involved in establishing LR asymmetry during early development. Humans who suffer from dysfunctional cilia often develop conditions such as heterotaxy, where internal organs appear to be placed randomly. As a consequence to this failure in asymmetry development, serious complications such as congenital heart defects (CHD) occur. The mammalian (or mechanistic) target of rapamycin (mTOR) pathway has recently emerged as an important regulator regarding symmetry breaking. The mTOR pathway governs fundamental processes such as protein translation or metabolism. Its activity can be transduced by two complexes, which are called TORC1 and TORC2, respectively. So far, only TORC1 has been implicated with asymmetry development and appears to require very precise regulation. A number of recent papers provided evidence that dysregulated TORC1 results in alterations of motile cilia and asymmetry defects. In here, we give an update on what we know so far of mTORC1 in LR asymmetry development.

Tuberous Sclerosis Complex: new criteria for diagnostic work-up and management

Tuberous sclerosis complex (TSC) is a rare genetic multisystem disorder, characterized by predominantly benign tumors in potentially all organ systems. System involvement, severity of clinical symptoms and the response to treatment are age-dependent and heterogeneous. Consequently, the disorder is still not recognized in a considerable number of patients. The diagnostic criteria and the guidelines for surveillance and management of patients with TSC were revised, and the establishment of specialized TSC-centers was strongly recommended during an International Consensus Conference in 2012. TOSCA (TuberOus SClerosis registry to increase disease Awareness), an international patient registry, was started to allow new insights into the causes of different courses. Finally, there are-since the approval of the mTOR inhibitor Everolimus-promising new therapeutic approaches.This review focuses on the various TSC related symptoms occurring at different ages, the novel recommendations for diagnosis and treatment as well as the need for multidisciplinary follow-up.

Response to everolimus is seen in TSC-associated SEGAs and angiomyolipomas independent of mutation type and site in TSC1 and TSC2

Tuberous sclerosis complex is an autosomal dominant disorder that occurs owing to inactivating mutations in either TSC1 or TSC2. Tuberous sclerosis complex-related tumors in the brain, such as subependymal giant cell astrocytoma, and in the kidney, such as angiomyolipoma, can cause significant morbidity and mortality. Recently, randomized clinical trials (EXIST-1 and EXIST-2) of everolimus for each of these tuberous sclerosis complex-associated tumors demonstrated the benefit of this drug, which blocks activated mammalian target of rapamycin complex 1. Here we report on the spectrum of mutations seen in patients treated during these trials and the association between mutation and response. TSC2 mutations were predominant among patients in both trials and were present in nearly all subjects with angiomyolipoma in whom a mutation was identified (97%), whereas TSC1 mutations were rare in those subjects (3%). The spectrum of mutations seen in each gene was similar to those previously reported. In both trials, there was no apparent association between mutation type or location within each gene and response to everolimus. Everolimus responses were also seen at a similar frequency for the 16–18% of patients in each trial in whom no mutation in either gene was identified. These observations confirm the strong association between TSC2 mutation and angiomyolipoma burden seen in previous studies, and they indicate that everolimus response occurs regardless of mutation type or location or when no mutation in TSC1 or TSC2 has been identified.

Prolonging the survival of Tsc2 conditional knockout mice by glutamine supplementation

The genetic disease tuberous sclerosis complex (TSC) is an autosomal dominant disorder caused by loss of function mutations in either TSC1 (hamartin) or TSC2 (tuberin), which serve as negative regulators of mechanistic target of rapamycin complex 1 (mTORC1) activity. TSC patients exhibit developmental brain abnormalities and tuber formations that are associated with neuropsychological and neurocognitive impairments, seizures and premature death. Mechanistically, TSC1 and TSC2 loss of function mutations result in abnormally high mTORC1 activity. Thus, the development of a strategy to inhibit abnormally high mTORC1 activity may have therapeutic value in the treatment of TSC. mTORC1 is a master regulator of growth processes, and its activity can be reduced by withdrawal of growth factors, decreased energy availability, and by the immunosuppressant rapamycin. Recently, glutamine has been shown to alter mTORC1 activity in a TSC1-TSC2 independent manner in cells cultured under amino acid- and serum-deprived conditions. Since starvation culture conditions are not physiologically relevant, we examined if glutamine can regulate mTORC1 in non-deprived cells and in a murine model of TSC. Our results show that glutamine can reduce phosphorylation of S6 and S6 kinase, surrogate indicators of mTORC1 activity, in both deprived and non-deprived cells, although higher concentrations were required for non-deprived cultures. When administered orally to TSC2 knockout mice, glutamine reduced S6 phosphorylation in the brain and significantly prolonged their lifespan. Taken together, these results suggest that glutamine supplementation can be used as a potential treatment for TSC.

Tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is a neurocutaneous syndrome that can affect the brain, skin, eyes, kidneys, heart, and lungs. TSC alters cellular proliferation and differentiation, resulting in hamartomas of various organs, tumor formation, and altered neuronal migration. The phenotype is highly variable. Most individuals have seizures, commonly including infantile spasms, and there is variable intellectual disability and autism. Neonates can present with cardiac failure due to intracardiac rhabdomyomas. The likelihood of renal angiomyolipomas increases with age, and renal disease is the most common cause of death in adults with TSC. Pulmonary involvement occurs predominantly in women and carries a high morbidity and mortality. TSC is inherited as an autosomal dominant trait, but spontaneous mutations are common. A mutation of either TSC1 on chromosome 9 or TSC2 on chromosome 16 leads to dysfunction of hamartin or tuberin, respectively. These two proteins form a functional complex that modulates the mammalian target of rapamycin (mTOR) pathway. Medications that inhibit mTOR are being used to treat TSC-related tumors, and current studies are investigating whether these agents could alleviate other TSC complications. Consensus statements guide identification and optimal management of many of the TSC-related complications at diagnosis and throughout the lifespan. A multidisciplinary approach is necessary for optimal management of individuals with TSC.

Myocardial fat overgrowth in Proteus syndrome

Proteus syndrome (PS) is a rare, mosaic disorder with asymmetric and distorting overgrowth of the skeletal system, skin, and adipose tissues. Cardiac abnormalities are rare in this syndrome and only two prior cases have been reported. Many patients with PS followed at our institution underwent transthoracic echocardiograms for preoperative evaluation or as work-up for associated pulmonary disease. Some were noted to have prominent, focal echodense areas in the myocardium. We further investigated cardiac findings in a cohort of children and adult patients with PS. Patients with abnormal echocardiograms were referred for cardiac magnetic resonance imaging, Holter monitoring, and exercise treadmill testing. Twenty children and adults with PS, age 24 months to 50 years old, underwent transthoracic echocardiograms. Seven patients (35%) had focal bright echodense areas within the myocardium suggesting fatty infiltration. The majority of patients had significant involvement of the interventricular septum. The cardiac characteristics of all patients with fatty infiltration on transthoracic echocardiograms were compared to Proteus patients without these findings. There were no significant differences in chamber sizes, mass, systolic or diastolic function. No increased risk of conduction defects or arrhythmias was found. This study shows that abnormal fat overgrowth is a common finding in the myocardium in patients with Proteus syndrome; however, it is not associated with functional derangements or arrhythmias. Further evaluation of a larger number of Proteus patients is needed in order to determine the frequency and prognosis of cardiac involvement. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

The analysis of mutations and exon deletions at TSC2 gene in angiomyolipomas associated with tuberous sclerosis complex

Angiomyolipomas (AMLs) are relatively rare hamartomatous or benign tumors that occasionally occur as part of tuberous sclerosis complex (TSC). Mutations in either of the two genes, TSC1 and TSC2, have been attributed to the development of TSC. Between 1994 and January 2009, 83 patients were diagnosed with AML at the Samsung Medical Center. In that group of patients, 5 (6%) had AML with TSC (AML-TSC). Mutational analysis of the TSC2 gene was performed using 7 samples from the 5 AML-TSC patients and 14 samples from 14 patients with sporadic AML without TSC (AML-non-TSC). From this analysis, mutations in TSC genes were identified in 5 samples from the AML-TSC patients (mutation detection rate=71%) and 3 samples from AML-non-TSC patients (mutation detection rate=21%). In the case of AML-TSC, 6 mutations were found including 3 recurrent mutations and 3 novel mutations, while in the case of AML-non-TSC, 4 mutations were identified once, including 1 novel mutation. Also MLPA analysis of the TSC2 gene showed that TSC2 exon deletion is more frequently observed in AML-TSC patients than in AML-non-TSC patients. This is the first mutation and multiplex ligation-dependent probe amplification (MLPA) analyses of TSC2 in Korean AMLs that focus on TSC. This study provides data that are representative of the distribution of mutations and exon deletions at TSC genes in clinically diagnosed AML-TSC cases of the Korean population.

Transgenic expression of the N525S-tuberin variant in Tsc2 mutant (Eker) rats causes dominant embryonic lethality

The Tsc2 product, tuberin, negatively regulates the mTOR pathway. We have exploited the Eker (Tsc2-mutant) rat system to analyse various Tsc2 mutations. Here, we focus on the N525S-Tsc2 variant (NSM), which is known to cause distinct symptoms in patients even though normal suppression of mTOR is observed. Unexpectedly, we were repeatedly unable to generate viable rats carrying the NSM transgene. Genotypic analysis revealed that most of the embryos carrying the transgene died around embryonic day after 14.5—similar to the stage of lethality observed for Eker homozygotes. Thus, the NSM transgene appeared to have a dominant lethal effect in our rat model. Further, no significant differences were observed for various signal transduction molecules in transiently expressed NSM cells compared to WT. These results indicate that a non-mTOR pathway, critical for embryogenesis, is being regulated by tuberin, providing a link between tuberin expression and the severity of Tsc2 mutation-related pathogenesis.

Both maternal and pup genotype influence ultrasonic vocalizations and early developmental milestones in tsc2 (+/-) mice

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by tumor growth and neuropsychological symptoms such as autistic behavior, developmental delay, and epilepsy. While research has shed light on the biochemical and genetic etiology of TSC, the pathogenesis of the neurologic and behavioral manifestations remains poorly understood. TSC patients have a greatly increased risk of developmental delay and autism spectrum disorder, rendering the relationship between the two sets of symptoms an extremely pertinent issue for clinicians. We have expanded on previous observations of aberrant vocalizations in Tsc2^+/− mice by testing vocalization output and developmental milestones systematically during the early postnatal period. In this study, we have demonstrated that Tsc2 haploinsufficiency in either dams or their pups results in a pattern of developmental delay in sensorimotor milestones and ultrasonic vocalizations.

The mutational spectrum of the NF1 gene in neurofibromatosis type I patients from UAE

INTRODUCTION

Germline heterozygous mutations in the tumor suppresser NF1 gene cause a cancer predisposition syndrome known as neurofibromatosis type 1 (NF1). This disease is one of the most common multisystem disorders with an estimated incidence of 1 in 3,000 to 1 in 4,000 births. Clinically, NF1 patients are prone to develop "café au lait" spots, neurofibromas, Lisch nodules, freckling of the axillary, or inguinal region and optic nerve gliomas.

MATERIALS AND METHODS

In the present study, we report clinical and molecular findings of five unrelated patients and seven cases from four families with NF1 from UAE. To reveal the genetic defects underlying NF1 in our cohort of patients, we screened the whole coding and splice site regions of the NF1 gene. In addition, MLPA or CGH array has been used to screen for structural variations including deletions, indels, and complex rearrangements.

RESULTS

This resulted in the identification of five distinct novel mutations and two previously reported ones. These variations included three missense and one nonsense mutations, one single base, one dinucleotide, and one large deletion.

CONCLUSION

Four mutations were inherited, and the remaining were absent from both parents and therefore are "de novo" mutations. This analysis represents the spectrum of NF1 mutations in UAE and supports the premise of absence of hotspot mutations in the NF1 gene. Moreover, no obvious genotype-phenotype correlations were observed in our patients.

Comparative analysis of Tsc1 and Tsc2 single and double radial glial cell mutants

Tuberous sclerosis complex (TSC) is a neurodevelopmental disorder with variable expressivity. Heterozygous mutations in either of two genes, TSC1 (hamartin) or TSC2 (tuberin), are responsible for most cases. Hamartin and tuberin form a heterodimer that functions as a major cellular inhibitor of the mammalian target of rapamycin complex 1 (mTORC1) kinase. Genotype-phenotype studies suggest that TSC2 mutations are associated with a more severe neurologic phenotype, although the biologic basis for the difference between TSC1- and TSC2-based disease is unclear. Here we performed a study to compare and contrast the brain phenotypes of Tsc1 and Tsc2 single and double mutants. Using Tsc1 and Tsc2 floxed alleles and a radial glial transgenic Cre driver (FVB-Tg(GFAP-cre)25Mes/J), we deleted Tsc1 and/or Tsc2 in radial glial progenitor cells. Single and double mutants had remarkably similar phenotypes: early postnatal mortality, brain overgrowth, laminar disruption, astrogliosis, a paucity of oligodendroglia, and myelination defects. Double Tsc1/Tsc2 mutants died earlier than single mutants, and single mutants showed differences in the location of heterotopias and the organization of the hippocampal stratum pyramidale. The differences were not due to differential mTORC1 activation or feedback inhibition on Akt. These data provide further genetic evidence for individual hamartin and tuberin functions that may explain some of the genotype-phenotype differences seen in the human disease.

Genome at juncture of early human migration: a systematic analysis of two whole genomes and thirteen exomes from Kuwaiti population subgroup of inferred Saudi Arabian tribe ancestry

Population of the State of Kuwait is composed of three genetic subgroups of inferred Persian, Saudi Arabian tribe and Bedouin ancestry. The Saudi Arabian tribe subgroup traces its origin to the Najd region of Saudi Arabia. By sequencing two whole genomes and thirteen exomes from this subgroup at high coverage (>40X), we identify 4,950,724 Single Nucleotide Polymorphisms (SNPs), 515,802 indels and 39,762 structural variations. Of the identified variants, 10,098 (8.3%) exomic SNPs, 139,923 (2.9%) non-exomic SNPs, 5,256 (54.3%) exomic indels, and 374,959 (74.08%) non-exomic indels are 'novel'. Up to 8,070 (79.9%) of the reported novel biallelic exomic SNPs are seen in low frequency (minor allele frequency <5%). We observe 5,462 known and 1,004 novel potentially deleterious nonsynonymous SNPs. Allele frequencies of common SNPs from the 15 exomes is significantly correlated with those from genotype data of a larger cohort of 48 individuals (Pearson correlation coefficient, 0.91; p <2.2×10-16). A set of 2,485 SNPs show significantly different allele frequencies when compared to populations from other continents. Two notable variants having risk alleles in high frequencies in this subgroup are: a nonsynonymous deleterious SNP (rs2108622 [19:g.15990431C>T] from CYP4F2 gene [MIM:*604426]) associated with warfarin dosage levels [MIM:#122700] required to elicit normal anticoagulant response; and a 3' UTR SNP (rs6151429 [22:g.51063477T>C]) from ARSA gene [MIM:*607574]) associated with Metachromatic Leukodystrophy [MIM:#250100]. Hemoglobin Riyadh variant (identified for the first time in a Saudi Arabian woman) is observed in the exome data. The mitochondrial haplogroup profiles of the 15 individuals are consistent with the haplogroup diversity seen in Saudi Arabian natives, who are believed to have received substantial gene flow from Africa and eastern provenance. We present the first genome resource imperative for designing future genetic studies in Saudi Arabian tribe subgroup. The full-length genome sequences and the identified variants are available at ftp://dgr.dasmaninstitute.org and http://dgr.dasmaninstitute.org/DGR/gb.html.

Wide spectrum of clinical manifestations in children with tuberous sclerosis complex--follow-up of 20 children

TSC is a multisystem genetic disorder predisposing to multiple organ manifestations and developmental problems. Clinical follow-up of patients remains a challenge for the caring paediatrician.

METHODS

We performed a retrospective analysis of clinical manifestations, diagnostic and therapeutic data in 20 children with the diagnosis of tuberous sclerosis complex (TSC) to answer the following questions: are the clinical guidelines and imaging strategies appropriate to discover complications, are there significant early predictors of long-term prognosis, what is the age range for signs and symptoms to occur.

RESULTS

Cardiac rhabdomyoma were present in 18 children and occurred as earliest manifestation. 8 of these exhibited associated arrhythmia or congenital cardiac anomalies. Seizures combined with cortical tubers and subependymal nodules occurred in 18 patients and were most likely to start in infancy, which was associated with later cognitive impairment. Cutaneous manifestations (15 children) occurred in late childhood and school age, whilst renal angiomyolipomas (11) developed in puberty.

DISCUSSION

The clinical course and imaging strategies are compared with data from previous studies. A review of TSC in regard to the multiple manifestations is provided.

Renal manifestations of tuberous sclerosis among children: an Indian experience and review of the literature

Objective

The objective of this study was to describe the renal manifestations in children 0–18 years of age diagnosed with tuberous sclerosis complex (TSC) at a tertiary hospital in South India.

Methods

Data of children with TSC, who presented to Christian Medical College Vellore Hospital from January 2008 to January 2013, were analysed by a retrospective chart review. The cases were identified from outpatient records and underwent ultrasonography, urine analysis and examination of serum creatinine to recognize renal involvement.

Results

Twenty-five children with TSC were identified. Two children did not have imaging studies available and were excluded from the analysis. The age of the included children ranged from 5 days to 15 years with a median age of 8 years. Seventy-four per cent (17/23) were males. Ten of the 23 children had evidence of renal involvement (43.5%). Of the 10 children with renal involvement, 6 had angiomyolipoma (60%), 5 had renal cysts (50%) and 1 had suspected renal cell carcinoma. In two children both angiomyolipoma (AML) and cysts were noted. One child was found to have proteinuria. The rest of the children had no evidence of proteinuria and had normal creatinine clearance.

Conclusion

We conclude that all children with TSC should be screened for renal involvement and regular follow-up should be arranged.

Epilepsy in TSC: certain etiology does not mean certain prognosis

PURPOSE

Prevalence and long-term outcome of epilepsy in tuberous sclerosis complex (TSC) is reported to be variable, and the reasons for this variability are still controversial.

METHODS

We reviewed the clinical characteristics of patients with TSC who were regularly followed since 2000 at the San Paolo Multidisciplinary Tuberous Sclerosis Centre in Milan, Italy. From patient charts we collected data about age at epilepsy onset, seizure frequency and seizure type, history of infantile spasms (IS), epileptic syndrome, evolution to refractory epilepsy or to seizure freedom and/or medication freedom, electroencephalography (EEG) features, magnetic resonance imaging (MRI) findings, cognitive outcome, and genetic background.

KEY FINDINGS

Among the 160 subjects (120 adults and 40 children), 116 (72.5%) had epilepsy: 57 (35.6%) were seizure-free, and 59 (36.9%) had drug-resistant epilepsy. Most seizure-free patients had a focal epilepsy (89.5%), with 54.4% of them drug resistant for a period of their lives. Epilepsy onset in the first year of life with IS and/or focal seizures was characteristic of the drug-resistant group of patients, as well as cognitive impairment and TSC2 mutation (p < 0.05). A small group of patients (7 patients, 4.4%) experienced a seizure only once; all of them had normal cognition.

SIGNIFICANCE

Although epilepsy management can be challenging in TSC, more than one third of patients had their seizures controlled: through monotherapy in 56% and by polytherapy in 32%. Moreover, 12% of the patients became seizure-free and were off medication. Identifying predictive features of epilepsy and cognitive outcome can ensure better management for patients with TSC and delineate genotype-phenotype correlations.

A tuberous sclerosis complex signalling node at the peroxisome regulates mTORC1 and autophagy in response to ROS

Subcellular localization is emerging as an important mechanism for mTORC1 regulation. We report that the tuberous sclerosis complex (TSC) signaling node, TSC1, TSC2 and Rheb, localizes to peroxisomes, where it regulates mTORC1 in response to reactive oxygen species (ROS). TSC1 and TSC2 were bound by PEX19 and PEX5, respectively, and peroxisome-localized TSC functioned as a Rheb GAP to suppress mTORC1 and induce autophagy. Naturally occurring pathogenic mutations in TSC2 decreased PEX5 binding, abrogated peroxisome localization, Rheb GAP activity, and suppression of mTORC1 by ROS. Cells lacking peroxisomes were deficient in mTORC1 repression by ROS and peroxisome-localization deficient TSC2 mutants caused polarity defects and formation of multiple axons in neurons. These data identify a role for TSC in responding to ROS at the peroxisome, and identify the peroxisome as a signaling organelle involved in regulation of mTORC1.

Frequency of TSC1 and TSC2 mutations in American, British, Polish and Taiwanese populations

Tuberous sclerosis (TS) is caused by mutation of the tumor suppressor genes, tuberous sclerosis complex 1 (TSC1) or 2 (TSC2). The aim of the present study was to compare the frequency and types of TSC1 and TSC2 mutations in American, British, Polish and Taiwanese populations. A meta‑analysis of 380 TS patients was performed. Significant differences were analyzed using the Chi-square test and one-way ANOVA analysis. Results showed a difference in frequency for the four populations analyzed. The frequency of TSC1 mutations was twice as high in the American and British populations. However, there were no significant differences in the types of mutations, with insertions of >1 nucleotide being the least frequent. Additionally, in an analysis of the complexity of nucleotide sequences it was demonstrated that the level of sequence complexity in the Polish population was significant higher compared to the remaining populations. Concerning strand bias, in the case of two types of substitutions, C>G/G>C and C>T/G>A, the ratio of corresponding mutations on the two DNA strands was approximately 3:1 and 2:1. In the present study, an increased frequency of C>G/G>C and C>T/G>A mutations in the coding strand was found in the analyzed populations. However, additional studies and larger patient cohorts are required to verify these results.

Trends in the prevalence of tuberous sclerosis complex manifestations: an epidemiological study of 166 Japanese patients

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder with multi-system involvement and variable manifestations. There has been significant progress in TSC research and the development of technologies used to diagnose this disorder. As a result, individuals with mild TSC are now being diagnosed, including many older adults who have not developed seizures or cognitive abnormalities. We conducted a statistical analysis of the frequency of TSC manifestations in a population of Japanese adults and children, comparing our findings with historical data. The chi-square test was used to examine the frequency of each manifestation by age. A total of 166 outpatients at the Department of Dermatology of Osaka University Hospital during the period from January 2001 to March 2011 were included in the study. Compared to previous reports, the frequency of neurologic manifestations (excepting autism) was lower in this cohort, and the frequency of skin manifestations (excepting hypomelanotic macules) was higher in this cohort. The frequencies of pulmonary lymphangioleiomyomatosis and renal manifestations were not significantly different from those previously reported. Regarding the association of each manifestation with age, the frequency of neurologic manifestations (excepting subependymal giant cell astrocytoma) was significantly higher in younger patients than in older patients. The frequency of skin manifestations and renal angiomyolipoma were significantly higher in older patients than in younger patients. Because of their high frequency and visibility, skin manifestations are useful in the diagnosis of TSC. Moreover, uterine perivascular epithelioid cell tumor was also characterized as a new findings associated with TSC.

Evolving neurobiology of tuberous sclerosis complex

Over the past decade, there have been numerous advances in our understanding of the molecular pathogenesis of tuberous sclerosis complex (TSC). Following the identification of the TSC1 and TSC2 genes, a link to regulatory control of the mammalian target of rapamycin (mTOR) signaling pathway has paved the way for new therapeutic interventions, and now even approved therapies for TSC. Gene identification has permitted establishment of cell lines and conditional knockout mouse strains to assay how abnormalities in brain structure lead to enhanced excitability, seizures, cognitive disabilities, and other neuropsychological disorders in TSC. Furthermore, work in in vitro systems and analysis of rodent models and human tissue has allowed investigators to study how brain lesions form in TSC. Evolving questions over the next decade include understanding the high clinical variability of TSC, defining why there is a lack of clear genotype-phenotype correlations, and identifying biomarkers for prognosis and stratification. The study of TSC has in many ways reflected a paradigm "bench-to-bedside" success story that serves as a model of many other neurological disorders.

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.

A magnetic resonance imaging study of cerebellar volume in tuberous sclerosis complex

The cerebellum plays an important role in motor learning and cognition, and structural cerebellar abnormalities have been associated with cognitive impairment. In tuberous sclerosis complex, neurologic outcome is highly variable, and no consistent imaging or pathologic determinant of cognition has been firmly established. The cerebellum calls for specific attention because mouse models of tuberous sclerosis complex have demonstrated a loss of cerebellar Purkinje cells, and cases of human histologic data have demonstrated a similar loss in patients. We hypothesized that there might be a common cerebellar finding in tuberous sclerosis complex that could be measured as morphometric changes with magnetic resonance imaging. Using a robust, automated image analysis procedure, we studied 36 patients with tuberous sclerosis complex and age-matched control subjects and observed significant volume loss among patients in the cerebellar cortices and vermis. Furthermore, this effect was strongest in a subgroup of 19 patients with a known, pathogenic mutation of the tuberous sclerosis 2 gene and impacted all cerebellar structures. We conclude that patients with tuberous sclerosis complex exhibit volume loss in the cerebellum, and this loss is larger and more widespread in patients with a tuberous sclerosis 2 mutation.

Tuberous sclerosis complex

Tuberous Sclerosis Complex, also known as Epiloia or Bourneville-Pringle disease is an autosomal dominant neurocutaneous syndrome with variable clinical expression. It is a multisystem disorder that may be associated with hamartomas in multiple organs in an unpredictable manner. The dermatologist plays an essential role in the history of the disease, since skin manifestations represent the most prevalent clinical features, enabling early diagnosis and intervention in its natural course. This article aims to inform the scientific community about advances made in the study of genetics and molecular biology. Recent findings regarding stimulation of tumor growth have been changing the history of this condition, making therapeutic trials with topical and systemic drugs possible. Knowledge of these topics enables better management of the patients affected, since tissue replacement by tumors can result in significant morbidity and mortality.

Probing the GTPase cycle with real-time NMR: GAP and GEF activities in cell extracts

The Ras superfamily of small GTPases is a large family of switch-like proteins that control diverse cellular functions, and their deregulation is associated with multiple disease processes. When bound to GTP they adopt a conformation that interacts with effector proteins, whereas the GDP-bound state is generally biologically inactive. GTPase activating proteins (GAPs) promote hydrolysis of GTP, thus impeding the biological activity of GTPases, whereas guanine nucleotide exchange factors (GEFs) promote exchange of GDP for GTP and activate GTPase proteins. A number of methods have been developed to assay GTPase nucleotide hydrolysis and exchange, as well as the activity of GAPs and GEFs. The kinetics of these reactions are often studied with purified proteins and fluorescent nucleotide analogs, which have been shown to non-specifically impact hydrolysis and exchange. Most GAPs and GEFs are large multidomain proteins subject to complex regulation that is challenging to reconstitute in vitro. In cells, the activities of full-length GAPs or GEFs are typically assayed indirectly on the basis of nucleotide loading of the cognate GTPase, or by exploiting their interaction with effector proteins. Here, we describe a recently developed real-time NMR method to assay kinetics of nucleotide exchange and hydrolysis reactions by direct monitoring of nucleotide-dependent structural changes in an isotopically labeled GTPase. The unambiguous readout of this method makes it possible to precisely measure GAP and GEF activities from extracts of mammalian cells, enabling studies of their catalytic and regulatory mechanisms. We present examples of NMR-based assays of full-length GAPs and GEFs overexpressed in mammalian cells.

Tuberous sclerosis complex: genotype/phenotype correlation of retinal findings

OBJECTIVE

To evaluate genotype/phenotype correlations in individuals with astrocytic hamartoma (AH) and retinal achromic patch (AP) in the setting of tuberous sclerosis complex (TSC).

DESIGN

Retrospective consecutive case series.

PARTICIPANTS

A total of 132 patients enrolled in the Cleveland Clinic Foundation Tuberous Sclerosis Program (CCF-TSCP) and 907 patients from the Tuberous Sclerosis Alliance (TSC-A).

METHODS

Patient gender, age at TSC diagnosis, presence of TSC1 or TSC2 mutations, detailed ophthalmic examination findings, systemic manifestations, and whether or not the patient had a diagnosis of epilepsy or cognitive impairment were analyzed.

MAIN OUTCOME MEASURES

Genotype/phenotype correlation of retinal findings and systemic disease manifestations.

RESULTS

No significant difference was found in the prevalence of AH or AP in the CCF-TSCP (36.1%) and TSC-A (34.1%) groups (P = 0.743). Astrocytic hamartomas were bilateral in 43.3% and 18.1% (P=0.009) and multiple in 40.0% and 15.3% (P = 0.008) in the CCF-TSCP and TSC-A groups, respectively. In the CCF-TSCP group, the average number of AH was 4 (range, 2-7). Average tumor size was 1.0 disc diameter (range, 0.5-2.5 disc diameters). The most common location was along the arcades (41.5%), adjacent to the optic nerve (29.2%), and in the retinal periphery (27.7%). In the CCF-TSCP group, AP was observed in 12.0% of patients (40.0% bilateral, 50.0% multiple). The presence of retinal features was associated with giant cell astrocytoma (37.1% vs. 14.6%; P = 0.018), renal angiomyolipoma (60.0% vs. 27.1%; P = 0.003), cognitive impairment (77.1% vs. 43.8%; P = 0.002), and epilepsy (91.4% vs. 70.8% (P = 0.022) in those with and without retinal findings, respectively. In patients with retinal findings in both the CCF-TSCP and TSC-A groups, mutations in TSC2 were more frequent than in TSC1, 3.3 times and 5.8 times, respectively; in those without retinal findings, the relative rates were 0.67 times and 2.3 times, respectively.

CONCLUSIONS

Individuals with retinal findings are more likely to have concomitant subependymal giant cell astrocytomas, renal angiomyolipomas, cognitive impairment, and epilepsy. TSC2 mutations are more frequent in patients with retinal findings than in those without retinal findings.

Giant angiofibromas in tuberous sclerosis complex: a possible role for localized lymphedema in their pathogenesis

BACKGROUND

Giant angiofibromas in patients with tuberous sclerosis complex (TSC) are rare.

OBJECTIVE

We sought to report two patients who had TSC with unusually large and disfiguring facial angiofibromas and to identify underlying histopathologic changes that may possibly explain the clinical features.

METHODS

We performed a clinicopathologic, immunohistochemical, and molecular biologic study using 42 lesional specimens and peripheral blood from one of the two patients. The immunohistochemical investigations were mainly focused on the vascular moiety of the lesions. TSC1 and TSC2 alterations were studied using multiplex ligation-dependent probe amplification for large deletion/duplication mutations, whereas screening for small mutations was performed using polymerase chain reaction amplification of individual coding exons and exon-intron junctions of both genes followed by an analysis on denaturation gradient gel electrophoresis.

RESULTS

Histopathologic examination revealed, in addition to findings typical of angiofibroma, several unusual features including multinucleated giant cells containing multiple intracytoplasmic vacuoles, Touton-like cells, emperipolesis, pagetoid dyskeratosis, vacuolar alteration at the dermoepidermal junction, Civatte bodies, and melanophages in the subjacent dermis. Numerous dilated lymphatic vessels were detected indicating localized lymphostasis, probably caused by secondary lymphedema. The lymphatic nature of the vessels was confirmed by immunohistochemical study. Genetic testing for TSC1 and TSC2 gene mutations revealed a substitution on position c.2251C>T resulting in a nonsense mutation R751X in fragment 20.2.

LIMITATIONS

Histopathologic specimens and peripheral blood were available from only one patient.

CONCLUSION

Localized lymphedema may contribute to the formation of large disfiguring angiofibromas in patients with TSC.

A developmental and genetic classification for malformations of cortical development: update 2012

Malformations of cerebral cortical development include a wide range of developmental disorders that are common causes of neurodevelopmental delay and epilepsy. In addition, study of these disorders contributes greatly to the understanding of normal brain development and its perturbations. The rapid recent evolution of molecular biology, genetics and imaging has resulted in an explosive increase in our knowledge of cerebral cortex development and in the number and types of malformations of cortical development that have been reported. These advances continue to modify our perception of these malformations. This review addresses recent changes in our perception of these disorders and proposes a modified classification based upon updates in our knowledge of cerebral cortical development.

Identification of TSC1 and TSC2 mutations in Korean patients with tuberous sclerosis complex

Tuberous sclerosis complex is a genetic disorder caused by mutations in the genes TSC1 or TSC2. Studies of these mutations are very rare in Korean populations. A previous study identified mutations in only 30% of patients by denaturing high performance liquid chromatography with sequencing. Here, we sought to determine the mutational frequency in Koreans. Eleven patients who fulfilled the diagnostic criteria for tuberous sclerosis complex were included. All patients underwent sequencing of both TSC genes, and if no mutations were evident, multiplex ligation-dependent probe amplification was performed. Mutations were detected by sequencing in 82% (9/11) of patients: 36.4% (4/11) in TSC1 and 45.5% (5/11) in TSC2. Two patients with no mutations carried large deletions that included exon 1 of TSC1 in one patient and exons 1-15 of TSC2 in the other patient. Mutations were completely identified in the present study. Therefore, mutation rates in Korean patients may not be lower than those in other ethnic groups. Direct sequencing followed by multiplex ligation-dependent probe amplification analysis may constitute a rational approach to identify disease-causing mutations in Korean patients.

Unusual cardiac "masses" in a newborn with infantile pompe disease

Glycogen storage disease type II (OMIM #232300), or Pompe disease, may present in the newborn period with moderate-to-severe biventricular hypertrophy with or without left ventricular outflow tract obstruction that typically leads to death from cardiorespiratory failure in the first year of life. Glycogen deposition tends to be uniform, and is only occasionally accompanied by patchy areas of fibrosis. Here, we present an infant identified with biventricular hypertrophy and cardiac masses by prenatal ultrasound. Postnatal molecular studies did not support the diagnosis of tuberous sclerosis in this case. Additional evaluation for infantile hypertrophic cardiomyopathy confirmed the diagnosis of Pompe disease. We discuss whether the "cardiac masses," which brought this infant to medical attention and facilitated an early diagnosis of Pompe disease, may represent an unusual manifestation of GSD type II or the coincidental occurrence of an unrelated disease process.

[Pathological aspects of the tumors of the lateral ventricles]

Typing a tumor of the lateral ventricle is often an issue, even for an experienced Neuropathologist. In this location are encountered specific entities, such as neurocytoma and subependymal giant cell astrocytoma, as well as more usual tumors, displaying a common misleading morphology, for instance a main clear cell component. The panel of diagnostic tools given to the pathologists has been increasing for a few years, enriched by immunohistochemical and molecular probes.

An Australian tuberous sclerosis cohort: are surveillance guidelines being met?

AIM

This study aims to describe the phenotypic and genotypic characteristics of 45 Australian patients with tuberous sclerosis complex (TSC), to assess risk factors for intellectual disability, to compare patients with TSC1 and TSC2 mutations and to assess adherence to surveillance recommendations.

METHODS

Phenotypic features were recorded in 45 patients who fulfilled established criteria for a diagnosis of definite TSC. All patients underwent TSC1 and TSC2 sequencing and multiplex ligand probe amplification. Features were compared in patients with TSC1 mutations versus TSC2 mutations. Recent surveillance was recorded at the point of first contact. Surveillance adherence was compared in the adult and paediatric cohorts.

RESULTS

This cohort consisted of 31 children and 14 adults with definite TSC. The rates of TSC manifestations and TSC1 and TSC2 mutation detection rates were consistent with previous studies. There was a trend towards greater severity for patients with TSC2 mutations compared with their TSC1 counterparts, particularly for autistic spectrum disorder, but this did not reach statistical significance. The presence of seizures was shown to be a risk factor for intellectual disability (P < 0.001). Overall, 12/45 patients (27%) were not undergoing recommended surveillance at the point of first contact. Surveillance guidelines were being followed in 3/31 (11%) children compared with 9/14 (64%) adult patients (P < 0.05).

CONCLUSIONS

The genotypic and phenotypic characteristics of this TSC cohort were consistent with previous studies. Surveillance rates in adult patients were significantly lower than in paediatric patients. This highlights the need for patients with TSC to undergo a focussed transition into adult services.

Horseshoe kidney and a rare TSC2 variant in two unrelated individuals with tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal dominant multisystem disorder characterized by abnormalities involving the skin, brain, kidney (angiomyolipomas, cysts), and heart. Horseshoe kidney has not been considered to be a common renal manifestation of TSC but it has been previously reported in two patients with TSC. We report on two unrelated females with typical manifestations of TSC, horseshoe kidney, and an identical variant c.5138G>A in exon 39 (p.Arg1713His) of TSC2 gene. These cases provide evidence that horseshoe kidney is associated with TSC and add to the evidence for the pathogenicity of this variant. Furthermore, one of the patients also had a diaphragmatic hernia which has been reported twice in the medical literature in individuals with TSC. It is possible that a diaphragmatic hernia is another rare manifestation of TSC and that TSC should be included in the differential diagnosis of infants with a diaphragmatic hernia. Given that both a horseshoe kidney and a diaphragmatic hernia are findings that can be detected prenatally on an ultrasound examination, our findings may have implications for prenatal genetic counseling.

Prenatal sonographic diagnosis of tuberous sclerosis complex

We report the case of a male fetus with tuberous sclerosis complex (TSC), in whom multiple cardiac rhabdomyomas and renal angiomyolipomas were detected at 33 weeks by ultrasound with additional brain lesions detected on MRI, all confirmed after birth. DNA analysis of the TSC2 gene detected a de novo mutation in the TSC2 gene. Postnatal follow-up and neurological examination were normal, as were the results of Holter monitoring.

Neuronal and glia abnormalities in Tsc1-deficient forebrain and partial rescue by rapamycin

Tuberous Sclerosis Complex (TSC) is a multiorgan genetic disease that prominently features brain malformations (tubers) with many patients suffering from epilepsy and autism. These malformations typically exhibit neuronal as well as glial cell abnormalities and likely underlie much of the neurological morbidity seen in TSC. Tuber pathogenesis remains poorly understood though upregulation of the mTORC1 signaling pathway in TSC has been consistently demonstrated. Here we address abnormal brain development in TSC by inactivating the mouse Tsc1 gene in embryonic neural progenitor cells. This strategy permits evaluation of the role of the Tsc1 gene in both neuronal as well as glial cell lineages. Tsc1(Emx1-Cre) conditional knockout (CKO) animals die by 25 days of life. Their brains have increased size and contain prominent large cells within the cerebral cortex that have greatly increased mTORC1 signaling and decreased mTORC2 signaling. Severe defects of cortical lamination, enlarged dysmorphic astrocytes and decreased myelination were also found. Tsc1(Emx1-Cre) CKO mice were then treated with rapamycin to see if the premature death and brain abnormalities can be rescued. Postnatal rapamycin treatment completely prevented premature death and largely reversed the glia pathology but not abnormal neuronal lamination. These findings support a model that loss of function of the TSC genes in embryonic neural progenitor cells causes cortical malformations in patients with TSC. The dramatic effect of rapamycin suggests that even with extensive multi-lineage abnormalities, a postnatal therapeutic window may exist for patients with TSC.

Clinically relevant imaging in tuberous sclerosis

Tuberous sclerosis (TS), also known as Bourneville disease or Bourneville–Pringle disease, is an autosomal dominant genetic disorder classically characterized by the presence of hamartomatous growths in multiple organs. TS and tuberous sclerosis complex (TSC) are different terms for the same genetic condition. Both terms describe clinical changes due to mutations involving either of the two genes named TSC1 and TSC2, which regulate cell growth. The diagnosis of TSC is established using diagnostic criteria based on clinical and imaging findings. Routine screening and surveillance of patients with TSC is needed to determine the presence and extent of organ involvement, especially the brain, kidneys, and lungs, and identify the development of associated complications. As the treatment is organ specific, imaging plays a crucial role in the management of patients with TSC.

Genetics and molecular biology of tuberous sclerosis complex

Tuberous Sclerosis Complex is a multisystem disorder exhibiting a wide range of manifestations characterized by tumour-like lesions called hamartomas in the brain, skin, eyes, heart, lungs and kidneys. Tuberous Sclerosis Complex is genetically determined with an autosomal dominant inheritance and is caused by inactivating mutations in either the TSC1 or TSC2 genes. TSC1/2 genes play a fundamental role in the regulation of phosphoinositide 3-kinase (PI3K) signalling pathway, inhibiting the mammalian target of rapamycin (mTOR) through activation of the GTPase activity of Rheb. Mutations in TSC1/2 genes impair the inhibitory function of the hamartin/tuberin complex, leading to phosphorylation of the downstream effectors of mTOR, p70 S6 kinase (S6K), ribosomal protein S6 and the elongation factor binding protein 4E-BP1, resulting in uncontrolled cell growth and tumourigenesis.

Despite recent promising genetic, diagnostic, and therapeutic advances in Tuberous Sclerosis Complex, continuing research in all aspects of this complex disease will be pivotal to decrease its associated morbidity and mortality. In this review we will discuss and analyse all the important findings in the molecular pathogenesis of Tuberous Sclerosis Complex, focusing on genetics and the molecular mechanisms that define this multisystemic disorder.