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

Human TSC2 Mutant Cells Exhibit Aberrations in Early Neurodevelopment Accompanied by Changes in the DNA Methylome

Tuberous Sclerosis Complex (TSC) is a debilitating developmental disorder characterized by a variety of clinical manifestations. While benign tumors in the heart, lungs, kidney, and brain are all hallmarks of the disease, the most severe symptoms of TSC are often neurological, including seizures, autism, psychiatric disorders, and intellectual disabilities. TSC is caused by loss of function mutations in the TSC1 or TSC2 genes and consequent dysregulation of signaling via mechanistic Target of Rapamycin Complex 1 (mTORC1). While TSC neurological phenotypes are well-documented, it is not yet known how early in neural development TSC1/2 -mutant cells diverge from the typical developmental trajectory. Another outstanding question is the contribution of homozygous-mutant cells to disease phenotypes and whether such phenotypes are also seen in the heterozygous-mutant populations that comprise the vast majority of cells in patients. Using TSC patient-derived isogenic induced pluripotent stem cells (iPSCs) with defined genetic changes, we observed aberrant early neurodevelopment in vitro , including misexpression of key proteins associated with lineage commitment and premature electrical activity. These alterations in differentiation were coincident with hundreds of differentially methylated DNA regions, including loci associated with key genes in neurodevelopment. Collectively, these data suggest that mutation or loss of TSC2 affects gene regulation and expression at earlier timepoints than previously appreciated, with implications for whether and how prenatal treatment should be pursued.

Clinical practice recommendations for kidney involvement in tuberous sclerosis complex: a consensus statement by the ERKNet Working Group for Autosomal Dominant Structural Kidney Disorders and the ERA Genes & Kidney Working Group

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by the presence of proliferative lesions throughout the body. Management of TSC is challenging because patients have a multifaceted systemic illness with prominent neurological and developmental impact as well as potentially severe kidney, heart and lung phenotypes; however, every organ system can be involved. Adequate care for patients with TSC requires a coordinated effort involving a multidisciplinary team of clinicians and support staff. This clinical practice recommendation was developed by nephrologists, urologists, paediatric radiologists, interventional radiologists, geneticists, pathologists, and patient and family group representatives, with a focus on TSC-associated kidney manifestations. Careful monitoring of kidney function and assessment of kidney structural lesions by imaging enable early interventions that can preserve kidney function through targeted approaches. Here, we summarize the current evidence and present recommendations for the multidisciplinary management of kidney involvement in TSC.

Malignant tumors in tuberous sclerosis complex: a case report and review of the literature

BACKGROUND

Tuberous sclerosis complex (TSC) is a rare, autosomal dominant genetic disease that arises from TSC1 or TSC2 genetic mutations. These genetic mutations can induce the development of benign tumors in any organ system with significant clinical implications in morbidity and mortality. In rare instances, patients with TSC can have malignant tumors, including renal cell carcinoma (RCC) and pancreatic neuroendocrine tumor (PNET). It is considered a hereditary renal cancer syndrome despite the low incidence of RCC in TSC patients. TSC is typically diagnosed in prenatal and pediatric patients and frequently associated with neurocognitive disorders and seizures, which are often experienced early in life. However, penetrance and expressivity of TSC mutations are highly variable. Herein, we present a case report, with associated literature, to highlight that there exist undiagnosed adult patients with less penetrant features, whose clinical presentation may contain non-classical signs and symptoms, who have pathogenic TSC mutations.

CASE PRESENTATION

A 31-year-old female with past medical history of leiomyomas status post myomectomy presented to the emergency department for a hemorrhagic adnexal cyst. Imaging incidentally identified a renal mass suspicious for RCC. Out of concern for hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome, the mass was surgically removed and confirmed as RCC. Discussion with medical genetics ascertained a family history of kidney cancer and nephrectomy procedures and a patient history of ungual fibromas on the toes. Genetic testing for hereditary kidney cancer revealed a 5'UTR deletion in the TSC1 gene, leading to a diagnosis of TSC. Following the diagnosis, dermatology found benign skin findings consistent with TSC. About six months after the incidental finding of RCC, a PNET in the pancreatic body/tail was incidentally found on chest CT imaging, which was removed and determined to be a well-differentiated PNET. Later, a brain MRI revealed two small cortical tubers, one in each frontal lobe, that were asymptomatic; the patient's history and family history did not contain seizures or learning delays. The patient presently shows no evidence of recurrence or metastatic disease, and no additional malignant tumors have been identified.

CONCLUSIONS

To our knowledge, this is the first report in the literature of a TSC patient without a history of neurocognitive disorders with RCC and PNET, both independently rare occurrences in TSC. The patient had a strong family history of renal disease, including RCC, and had several other clinical manifestations of TSC, including skin and brain findings. The incidental finding and surgical removal of RCC prompted the genetic evaluation and diagnosis of TSC, leading to a comparably late diagnosis for this patient. Reporting the broad spectrum of disease for TSC, including more malignant phenotypes such as the one seen in our patient, can help healthcare providers better identify patients who need genetic evaluation and additional medical care.

An updated meta-analysis of effectiveness and safety of mTOR inhibitors in the management of tuberous sclerosis complex patients

PURPOSE

Tuberculous sclerosis complex (TSC) is an autosomal dominant multi-system disease. In TSC patients, the inhibition of mTOR pathway is weakened, which leads to the uncontrolled proliferation of normal resting cells. Therefore, mTOR inhibitors have many therapeutic potentials in the treatment of TSC. However, there is no consensus on the safety and efficacy of mTOR inhibitors so far. This article aimed to present new evidence for the efficacy and safety of mTOR inhibitors in the treatment of TSC by evaluating published clinical trials.

METHODS

A systemic search of online databases, such as Cochrane Library, Embase, PubMed, and the US National Institutes of Health Clinical Trials Registry, was conducted. The researchers selected studies that met the following entry criteria: randomized, double-blinded or single-blinded, placebo-controlled, parallel-group studies with active and control arms receiving rapamycin or everolimus and matched placebo, respectively. The meta-analysis included seven studies. Tumor response or epilepsy seizure frequency response rates were considered efficacy outcomes.

RESULTS

In seven studies involving 877 patients, using of mTOR inhibitors therapy showed an improvement in both tumor response and seizure frequency outcomes in TSC. In combination of AML (angiomyolipomas), SEGA (subependymal giant cell astrocytoma), epilepsy, and facial angiofibroma subjects, the RR is 3.01 (95% CI 2.03 to 4.45, p = 0.000) with observed heterogeneity (I-squared = 55.4%). The main side effect of mTOR inhibitors was stomatitis.

CONCLUSION

The updated meta-analysis suggests that the use of mTOR inhibitors is an effective therapy for patients with TSC.

Case Report: Tuberous sclerosis complex-associated hemihypertrophy successfully treated with mTOR inhibitor sirolimus

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder caused by a mutation in either of the two tumor suppressor genes, TSC1 and TSC2. Due to dysregulated activity of the mammalian target of rapamycin (mTOR) pathway, hamartomas or benign tumors frequently occur in many organs and are often treated with mTOR inhibitors. Hemihypertrophy is a rare complication of TSC. Although not being a tumor, progressive overgrowth of the affected limb may cause cosmetic and functional problems, for which the efficacy of mTOR inhibitors has not been reported previously. We herein report a case of TSC-associated hemihypertrophy. In this case, genetic studies revealed TSC1 loss of heterozygosity as the cause of hemihypertrophy. Clinically, pharmacological treatment with an mTOR inhibitor sirolimus successfully ameliorated cosmetic and functional problems with no intolerable adverse effects.

Non-canonical functions of a mutant TSC2 protein in mitotic division

Tuberous Sclerosis Complex (TSC) is a debilitating developmental disorder characterized by a variety of clinical manifestations. TSC is caused by mutations in the TSC1 or TSC2 genes, which encode the hamartin/tuberin proteins respectively. These proteins function as a heterodimer that negatively regulates the mechanistic Target of Rapamycin Complex 1 (mTORC1). TSC research has focused on the effects of mTORC1, a critical signaling hub, on regulation of diverse cell processes including metabolism, cell growth, translation, and neurogenesis. However, non-canonical functions of TSC2 are not well studied, and the potential disease-relevant biological mechanisms of mutations affecting these functions are not well understood. We observed aberrant multipolar mitotic division, a novel phenotype, in TSC2 mutant iPSCs. The multipolar phenotype is not meaningfully affected by treatment with the inhibitor rapamycin. We further observed dominant negative activity of the mutant form of TSC2 in producing the multipolar division phenotype. These data expand the knowledge of TSC2 function and pathophysiology which will be highly relevant to future treatments for patients with TSC.

Neurofibromatosis type1, type 2, tuberous sclerosis and Von Hippel-Lindau disease

Neurocutaneous syndromes (also known as phakomatoses) are heterogenous group of disorders that involve derivatives of the neuroectoderm. Each disease has diagnostic and pathognomonic criteria, once identified, thorough clinical examination to the patient and the family members should be done. Magnetic resonance imaging (MRI) is used to study the pathognomonic findings withing the CNS (Evans et al. in Am J Med Genet A 152A:327-332, 2010). This chapter includes the 4 most common syndromes faced by neurosurgeons and neurologists; neurofibromatosis types 1 and 2, tuberous sclerosis and Von Hippel-Lindau disease. Each syndrome has specific genetic anomaly that involves a tumor suppressor gene and the loss of inhibition of specific pathways. The result is a spectrum of cutaneous manifestations and neoplasms.

Effect of mTOR Inhibitors in Epilepsy Treatment in Children with Tuberous Sclerosis Complex Under 2 Years of Age

INTRODUCTION

Mechanistic target of rapamycin (mTOR) inhibitors sirolimus and everolimus are an effective therapy for subependymal giant cell astrocytomas, cardiac rhabdomyomas, renal angiomyolipomas, and lymphangioleiomyomatosis associated with tuberous sclerosis complex (TSC). Everolimus was recently approved in the EU and the USA for the treatment of refractory focal-onset seizures. Despite frequent use of mTOR inhibitors, there are only a few studies on their effect on epilepsy control in children under 2 years of age. This study aims to assess the effect of adjunctive mTOR inhibitor treatment on seizure frequency in this age group.

METHODS

We performed retrospective data analysis of medical records of patients with TSC who initiated sirolimus or everolimus under the age of 2 years. Participants' antiseizure medication was adjusted according to their epilepsy control independently from mTOR inhibitor administration. The data was assessed separately for patients treated with mTOR inhibitors before and after the onset of seizures. We also compared the treatment group with a matched control group. The follow-up duration was up to 24 months.

RESULTS

Twenty-one patients with TSC from two clinical centers were included in the study. Nine participants had no history of seizures before mTOR inhibitor initiation. Twelve reported active epilepsy in the month prior to treatment initiation. Most patients treated preventively with mTOR inhibitors did not report active epilepsy at the end of their follow-up. In the second group, the mean frequency of seizures decreased with time. According to the comparative analysis, seizure control was better in the groups treated with mTOR inhibitors.

CONCLUSION

Patients with TSC treated with mTOR inhibitors demonstrated better seizure control than individuals without this treatment. Adjunctive pharmacotherapy with mTOR inhibitors appears to have a beneficial effect on epilepsy outcome in young children. Further prospective clinical trials should be conducted to determine the efficacy of mTOR inhibitors on epilepsy in patients with TSC under the age of 2 years.

Qualitative and quantitative evaluation for the heterogeneity of cortical tubers using structural imaging and diffusion-weighted imaging to predict the epileptogenicity in tuberous sclerosis complex patients

PURPOSE

We aimed to evaluate whether the heterogeneity of tuber imaging features, evaluated on the structural imaging and apparent diffusion coefficient (ADC) map, can facilitate detecting epileptogenic tubers before surgery in tuberous sclerosis complex (TSC) patients.

METHODS

Twenty-three consecutive patients, who underwent tuber resection at our institute, were retrospectively selected. A total of 125 tubers (39 epileptogenic, 86 non-epileptogenic) were used for the analysis. Tuber heterogeneity was evaluated, using a 5-point visual scale and standard deviation of ADC values (ADC_sd). A 5-point visual scale reflected the degree of T1/T2 prolongation, presence of internal cystic degeneration, and their spatial distribution within the tuber. These results were statistically compared between epileptogenic and non-epileptogenic groups, and their performance in predicting the epileptogenicity was also evaluated by receiver operating characteristic (ROC) analysis.

RESULTS

A 5-point visual scale demonstrated that more heterogeneous tubers were significantly more epileptogenic (p < 0.001). Multiplicity of internal cystic degeneration moderately correlated with epileptogenicity (p < 0.03) based on the comparison between class 4 and class 5 tubers. ADC_sd was significantly higher in epileptogenic tubers (p < 0.001). ROC curves revealed that a 5-point visual scale demonstrated higher area under the curve (AUC) value than ADC_sd (0.75 and 0.72, respectively).

CONCLUSION

Tuber heterogeneity may help identify the epileptogenic tubers in presurgical TSC patients. Visual assessment and standard deviation of ADC value, which are easier to implement in clinical use, may be a useful tool predicting epileptogenic tubers, improving presurgical clinical management for TSC patients with intractable epilepsy.

Reprint of: lessons from histopathologic examination of nephrectomy specimens in patients with tuberous sclerosis complex: cysts, angiomyolipomas & renal cell carcinoma

Renal manifestations in patients with tuberous sclerosis complex (TSC) include cysts, angiomyolipoma, and renal cell carcinoma. Unlike many hereditary predisposition syndromes, the spectrum of renal tumors in TSC patients (including both angiomyolipoma and renal cell carcinoma) is broad, with significant morphologic heterogeneity. An improved understanding of histopathologic findings in TSC patients and associated clinicopathologic correlates has significant implications not just in establishing a diagnosis of TSC, but also in the recognition of sporadic tumors occurring secondary to somatic alterations of TSC1/TSC2/MTOR pathway genes and accurate prognostication. In this review, we have discussed issues relevant to clinical management based on histopathologic findings in nephrectomy specimens from patients with TSC. This includes discussions related to screening for TSC, diagnosis of PKD1/TSC2 contiguous gene deletion syndrome, the morphologic spectrum of angiomyolipoma and renal epithelium-derived neoplasia, including the risk of disease progression.

Tuberin levels during cellular differentiation in brain development

Tuberin is a member of a large protein complex, Tuberous Sclerosis Complex (TSC), and acts as a sensor for nutrient status regulating protein synthesis and cell cycle progression. Mutations in the Tuberin gene, TSC2, permits the formation of tumors that can lead to developmental defects in many organ systems, including the central nervous system. Tuberin is expressed in the brain throughout development and levels of Tuberin have been found to decrease during neuronal differentiation in cell lines in vitro. Our current work investigates the levels of Tuberin at two stages of embryonic development in vivo, and we study the mRNA and protein levels during a time course using immortalized cell lines in vitro. Our results show that total Tuberin levels are tightly regulated through developmental stages in the embryonic brain. At a cell biology level, we show that Tuberin levels are higher when cells are cultured as neurospheres, and knockdown of Tuberin results in a reduction in the number of neurospheres. This functional data supports the hypothesis that Tuberin is an important regulator of stemness and the reduction of Tuberin levels might support functional differentiation in the central nervous system. Understanding how Tuberin expression is regulated throughout neural development is essential to fully comprehend the role of this protein in several developmental and neural pathologies.

Refractive Errors, Retinal Findings, and Genotype of Tuberous Sclerosis Complex: A Retrospective Cohort Study

PURPOSE

To examine the refractive errors, retinal manifestations, and genotype in tuberous sclerosis complex (TSC) patients in a Korean population.

MATERIALS AND METHODS

A total of 98 patients with TSC were enrolled in Severance Hospital for a retrospective cohort study. The number of retinal astrocytic hamartoma and retinal achromic patch within a patient, as well as the size, bilaterality, and morphological type were studied. In addition, the refractive status of patients and the comorbidity of intellectual disability and epilepsy were also examined.

RESULTS

Retinal astrocytic hamartoma was found in 37 patients, and bilateral invasion was observed in 20 patients (54%). TSC1 mutation was associated with myopia (p=0.01), while TSC2 mutation was associated with emmetropia (p=0.01). Retinal astrocytic hamartoma was categorized into three morphological types and examined as follows: type I (87%), type II (35%), and type III (14%). Single invasion of retinal astrocytic hamartoma was identified in 32% of the patients, and multiple invasions in 68%. The TSC1/TSC2 detection rate was 91% (41/45). Among them, TSC1 variant was detected in 23 patients (54%), whereas TSC2 variant was detected in 18 patients (40%). The results showed that TSC2 mutations are correlated with a higher rate of retinal astrocytic hamartoma involvement (all p<0.05), and multiple and bilateral involvement of retinal hamartomas (all p<0.05). However, the size of retinal astrocytic hamartomas, comorbidity of epilepsy, or intellectual disability did not show correlation with the genetic variant.

CONCLUSION

TSC1 variant patients were more myopic, while TSC2 variant patients showed association with more extensive involvement of retinal astrocytic hamartoma.

Learnings in developmental and epileptic encephalopathies: what do we know?

INTRODUCTION

Developmental and Epileptic Encephalopathies (DEEs) encompass a group of neurological disorders caused by either abnormal neuronal development and white matter maturation or even by weak synaptic plasticity. Hitherto, patients commonly have epileptic seizures featuring cognitive dysfunction, such as neurosensory disorders, difficulties in learning, behavioral disturbances, or speech delay.

AREAS COVERED

This paper provides a comprehensive review of the current knowledge of DEEs and cognition. Medline/Pubmed database was screened for in-English articles published between 1967-2022 dealing with the topic of DEEs and cognitive development. Two authors independently screened the title and abstract of each record and reviewed the selected articles. Reviews, randomized clinical trials, and case reports were selected.

EXPERT OPINION

Scientific literature has never explicitly dealt with the early neuro-psychomotor rehabilitation and neuropsychological assessment of patients with DEEs. Targeted intervention and environmental stimuli can influence the maturation of neuronal circuits and shape changes in physical and mental development based on neuronal plasticity, particularly if applied in 'critical periods' liable to heightened sensitivity. Thus, 'early neurorehabilitation interventions' are worthy of being more and more applied to clinical practice to improve the quality of life and reduce the psychosocial burden on families and caregivers.

Mosaicism in tuberous sclerosis complex: Lowering the threshold for clinical reporting

Tuberous sclerosis complex (TSC) is a multi-system genetic disorder. Most patients have germline mutations in TSC1 or TSC2 but, 10%-15% patients do not have TSC1/TSC2 mutations detected on routine clinical genetic testing. We investigated the contribution of low-level mosaic TSC1/TSC2 mutations in unsolved sporadic patients and families with TSC. Thirty-one sporadic TSC patients negative on routine testing and eight families with suspected parental mosaicism were sequenced using deep panel sequencing followed by droplet digital polymerase chain reaction. Pathogenic variants were found in 22/31 (71%) unsolved sporadic patients, 16 were mosaic (median variant allele fraction [VAF] 6.8% in blood) and 6 had missed germline mutations. Parental mosaicism was detected in 5/8 families (median VAF 1% in blood). Clinical testing laboratories typically only report pathogenic variants with allele fractions above 10%. Our findings highlight the critical need to change laboratory practice by implementing higher sensitivity assays to improve diagnostic yield, inform patient management and guide reproductive counseling.

Lessons from histopathologic examination of nephrectomy specimens in patients with tuberous sclerosis complex: cysts, angiomyolipomas, and renal cell carcinoma

Renal manifestations in patients with tuberous sclerosis complex (TSC) include cysts, angiomyolipoma, and renal cell carcinoma. Unlike many hereditary predisposition syndromes, the spectrum of renal tumors in TSC patients (including both angiomyolipoma and renal cell carcinoma) is broad, with significant morphologic heterogeneity. An improved understanding of histopathologic findings in TSC patients and associated clinicopathologic correlates has significant implications not just in establishing a diagnosis of TSC, but also in the recognition of sporadic tumors occurring secondary to somatic alterations of TSC1/TSC2/MTOR pathway genes and accurate prognostication. In this review, we have discussed issues relevant to clinical management based on histopathologic findings in nephrectomy specimens from patients with TSC. This includes discussions related to screening for TSC, diagnosis of PKD1/TSC2 contiguous gene deletion syndrome, the morphologic spectrum of angiomyolipoma and renal epithelium-derived neoplasia, including the risk of disease progression.

Cerebellar Tubers in Tuberous Sclerosis Complex Patients: New Imaging Characteristics and the Relationship with Cerebral Tubers

Objective The imaging characteristics, evolution, and clinical features of cerebellar tubers in tuberous sclerosis complex (TSC) patients have not been well described. The purpose of this study is to investigate the imaging characteristics of cerebellar tubers, including their dynamic changes, and to evaluate the relationship with cerebral tubers in TSC patients.

Materials and Methods Two observers retrospectively reviewed 75 consecutive TSC patients to identify cerebellar tubers and to evaluate their imaging characteristics, including location, presence of retraction change, calcification, contrast enhancement, and the presence of an associated vascular anomaly, as well as dynamic changes in these characteristics. The number of cerebral tubers was compared between TSC patients with and without cerebellar tubers.

Results Twenty-five TSC patients with 28 cerebellar tubers were identified. All cerebellar tubers occurred within the lateral portions of the cerebellar hemispheres. Thirteen cerebellar tubers demonstrated calcification. Ten cerebellar tubers showed contrast enhancement, half of which demonstrated a zebra-like appearance. A vascular anomaly was associated with 12 tubers, one of which subsequently developed parenchymal hemorrhage. Fifteen cerebellar tubers demonstrated complex dynamic changes in size and contrast enhancement. Patients with cerebellar tubers had more cerebral tubers (p = 0.001).

Conclusion Cerebellar tubers demonstrate a specific distribution, suggesting a possible influence on higher brain function. The presence of an associated vascular anomaly may be an important imaging characteristic. Cerebellar tubers may be associated with a more severe manifestation of TSC, given their association with increased numbers of cerebral tubers. These findings may provide insights into the pathogenesis and clinical manifestations of cerebellar tubers in TSC patients.

Genotype and Phenotype Landscape of 283 Japanese Patients with Tuberous Sclerosis Complex

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by multiple dysplastic organ lesions and neuropsychiatric symptoms, caused by loss of function mutations in either TSC1 or TSC2. Genotype and phenotype analyses are conducted worldwide, but there have been few large-scale studies on Japanese patients, and there are still many unclear points. This study analyzed 283 Japanese patients with TSC (225 definite, 53 possible, and 5 genetic diagnoses). A total of 200 mutations (64 TSC1, 136 TSC2) were identified, of which 17 were mosaic mutations, 11 were large intragenic deletions, and four were splicing abnormalities due to deep intronic mutations. Several lesions and symptoms differed in prevalence and severity between TSC1 and TSC2 patients and were generally more severe in TSC2 patients. Moreover, TSC2 missense and in-frame mutations may attenuate skin and renal symptoms compared to other TSC2 mutations. Genetic testing revealed that approximately 20% of parents of a proband had mild TSC, which could have been missed. The patient demographics presented in this study revealed a high frequency of TSC1 patients and a low prevalence of epilepsy compared to global statistics. More patients with mild neuropsychiatric phenotypes were diagnosed in Japan, seemingly due to a higher utilization of brain imaging, and suggesting the possibility that a significant amount of mild TSC patients may not be correctly diagnosed worldwide.

Tuberous sclerosis complex-associated nonfunctional pancreatic neuroendocrine tumors: Management and surgical outcomes

We aimed to further characterize pancreatic involvement in tuberous sclerosis complex (TSC), with a focus on management of TSC-associated nonfunctional pancreatic neuroendocrine tumors (PNETs). This was a retrospective chart review of a large cohort of TSC patients. A total of 637 patients with a confirmed diagnosis of TSC were seen at the Herscot Center for Tuberous Sclerosis Complex at Massachusetts General Hospital. Of the 637 total patients with a confirmed diagnosis of TSC, 28 patients were found to have varying pancreatic findings ranging from simple-appearing cysts to well-differentiated PNETs. Thirteen of the 28 patients had PNET confirmed on pathology; 10 of these tumors were resected at Massachusetts General Hospital. None of the patients had serious perioperative or postoperative complications; only one of the patients had a recurrence following resection. As roughly 4.4% of our TSC patient population had pancreatic involvement, surveillance abdominal imaging should include evaluation of the pancreas instead of limiting to a renal protocol. Additionally, given the low risk of complications and recurrence combined with documented risk of metastasis in TSC-associated PNET, TSC patients with pancreatic lesions suspicious for PNETs should be considered as surgical candidates.

Dissecting the roles of the Tuberin protein in the subcellular localization of the G2/M Cyclin, Cyclin B1

Tuberin is a major component of the protein regulatory complex known as the Tuberous Sclerosis Complex and plays a crucial role in cell cycle progression and protein synthesis. Mutations in the Tuberin gene, TSC2, lead to the formation of benign tumors in many organ systems and causes the Tuberous Sclerosis Complex disorder. Genotypes ranging from point mutations to large deletions in the TSC2 gene have been clinically characterized with a wide range of phenotypes from skin tumors to large brain tumors. Our lab has previously demonstrated that Tuberin can directly bind and regulate the timing of nuclear transport of the G2/M cyclin, Cyclin B1. Herein we study the consequence of one clinically relevant truncation in the Tuberin protein on cell cycle function. We demonstrate that exogenous expression of a fragment of the N-term region of Tuberin alters the subcellular localization of Cyclin B1 and increases cell proliferation. This adds to our body of information about the residues within Tuberin responsible for regulating the cytoplasmic retention of Cyclin B1 and supports the phenotypic data seen in the clinic with Tuberous Sclerosis Complex patients harbouring similar large deletions in Tuberin.

Raptor downregulation rescues neuronal phenotypes in mouse models of Tuberous Sclerosis Complex

Tuberous Sclerosis Complex (TSC) is a neurodevelopmental disorder caused by mutations in the TSC1 or TSC2 genes, which encode proteins that negatively regulate mTOR complex 1 (mTORC1) signaling. Current treatment strategies focus on mTOR inhibition with rapamycin and its derivatives. While effective at improving some aspects of TSC, chronic rapamycin inhibits both mTORC1 and mTORC2 and is associated with systemic side-effects. It is currently unknown which mTOR complex is most relevant for TSC-related brain phenotypes. Here we used genetic strategies to selectively reduce neuronal mTORC1 or mTORC2 activity in mouse models of TSC. We find that reduction of the mTORC1 component Raptor, but not the mTORC2 component Rictor, rebalanced mTOR signaling in Tsc1 knock-out neurons. Raptor reduction was sufficient to improve several TSC-related phenotypes including neuronal hypertrophy, macrocephaly, impaired myelination, network hyperactivity, and premature mortality. Raptor downregulation represents a promising potential therapeutic intervention for the neurological manifestations of TSC.

Monitoring and Managing Patients with Tuberous Sclerosis Complex: Current State of Knowledge

Tuberous sclerosis complex (TSC) is a rare genetic disease of autosomal dominant transmission that, in most cases, results from the presence of pathogenic variants of the TSC1 or TSC2 genes, encoding hamartin and tuberin, respectively. It is a multisystemic disease, affecting most frequently the brain, skin, kidney, and heart. The wide variety of possible clinical manifestations, given this multisystem dimension, makes the follow-up of patients with TSC an exercise of multidisciplinarity. In fact, these patients may require the intervention of various medical specialties, which thus have to combine their efforts to practice a medicine that is truly holistic. The past few years have witnessed a dramatic leap not only in the diagnosis and management of TSC patients, with standard monitoring recommendations, but also in the therapeutic field, with the use of mTORC1 inhibitors. In this article, we review the clinical manifestations associated with TSC, as well as the treatment and follow-up strategies that should be implemented, from a multidisciplinary perspective.

Genotype/phenotype correlation in 123 Chinese patients with Tuberous Sclerosis Complex

Tuberous Sclerosis Complex (TSC) is a multisystemic neurocutaneous disorder with autosomal dominant inheritance. We performed mutation analyses on 123 Chinese patients with "definite TSC" according to the latest diagnostic criteria. Pathogenic / likely-pathogenic variants were identified in 72.2% of all index patients (70/97), in which 35.7% (25/70) had TSC1 variants and 64.3% (45/70) had TSC2 variants. 84.5% (82/97) cases were sporadic and 15.5% (15/97) cases were familial. 62 unique variants were reported, in which 41.9% (26/62) were novel. Male patients had significantly more subependymal nodules (p=0.029) than females, whereas renal angiomyolipoma (p=0.032) occurred predominantly in females. Sporadic cases also had more renal angiomyolipoma (p=0.004), cortical tubers (p=0.008), hypopigmented macules (p=0.018) and fibrous cephalic plaques (p=0.028) than cases with known inheritance. Patients with TSC2 pathogenic variants were more likely to have mental retardation (p<0.001), cardiac rhabdomyoma (p=0.004), renal angiomyolipoma (p=0.006) and facial angiofibromas (p=0.026) than those with TSC1 pathogenic variants, while mutation-negative cases showed a mixed phenotype between those with TSC1 and TSC2 variants. There were no significant phenotypic differences between patients with and without TSC1/TSC2 variants, but TSC2 missense and in-frame variants were associated with higher frequencies of mental retardation (P<0.001), renal angiomyolipoma (p=0.001), cardiac rhabdomyoma (p=0.012) and facial angiofibroma (p=0.021) than those with TSC1 frameshift and splice site variants. Furthermore, a higher frequency of mental retardation (p=0.013) was observed in patients with TSC2 missense and in-frame variants than those with frameshift and splice site variants. All 14 antenatal-onset patients had cardiac rhabdomyoma. They had fewer seizures (p=0.028) than patients with paediatric-onset, but were more likely to have mental retardation (p=0.035) than individuals with adult-onset disease. Generally, paediatric-onset patients had more neurological manifestations, while initial presentations of adult-onset TSC were more diverse.

The association of neurodevelopmental abnormalities, congenital heart and renal defects in a tuberous sclerosis complex patient cohort

BACKGROUND

Tuberous sclerosis complex (TSC) is a rare multi-system genetic disorder characterised by the presence of benign tumours throughout multiple organs including the brain, kidneys, heart, liver, eyes, lungs and skin, in addition to neurological and neuropsychiatric complications. Intracardiac tumour (rhabdomyoma), neurodevelopmental disorders (NDDs) and kidney disorders (KD) are common manifestations of TSC and have been linked with TSC1 and TSC2 loss-of-function mutations independently, but the dynamic relationship between these organ manifestations remains unexplored. Therefore, this study aims to characterise the nature of the relationship specifically between these three organs' manifestations in TSC1 and TSC2 mutation patients.

METHODS

Clinical data gathered from TSC patients across South Wales registered with Cardiff and Vale University Health Board (CAV UHB) between 1990 and 2020 were analysed retrospectively to evaluate abnormalities in the heart, brain and kidney development. TSC-related abnormalities such as tumour prevalence, location and size were analysed for each organ in addition to neuropsychiatric involvement and were compared between TSC1 and TSC2 mutant genotypes. Lastly, statistical co-occurrence between organ manifestations co-morbidity was quantified, and trajectories of disease progression throughout organs were modelled.

RESULTS

This study found a significantly greater mutational frequency at the TSC2 locus in the cohort in comparison to TSC1. An equal proportion of male and female patients were observed in this group and by meta-analysis of previous studies. No significant difference in characterisation of heart involvement was observed between TSC1 and TSC2 patients. Brain involvement was seen with increased severity in TSC2 patients, characterised by a greater prevalence of cortical tubers and communication disorders. Renal pathology was further enhanced in TSC2 patients, marked by increased bilateral angiomyolipoma prevalence. Furthermore, co-occurrence of NDDs and KDs was the most positively correlated out of investigated manifestations, regardless of genotype. Analysis of disease trajectories revealed a more diverse clinical outcome for TSC2 patients: however, a chronological association of rhabdomyoma, NDD and KD was most frequently observed for TSC1 patients.

CONCLUSIONS

This study marks the first empirical investigation of the co-morbidity between congenital heart defects (CHD), NDDs, and KDs in TSC1 and TSC2 patients. This remains a unique first step towards the characterisation of the dynamic role between genetics, heart function, brain function and kidney function during the early development in the context of TSC.

Pancreatic Neuroendocrine Neoplasms: Updates on Genomic Changes in Inherited Tumour Syndromes and Sporadic Tumours Based on WHO Classification

Pancreatic neuroendocrine neoplasms (PanNENs) are the neuroendocrine neoplasms with greatest rate of increase in incidence. Approximately 10% of PanNENs arise as inherited tumour syndromes which include multiple endocrine neoplasia type 1, multiple endocrine neoplasia type 4, von Hippel-Lindau syndrome, neurofibromatosis type1, tuberous sclerosis complex 1/2, Cowden syndrome, and Glucagon cell hyperplasia and neoplasia as well as familial insulinomatosis. In sporadic PanNENs, driver mutations in MEN1, DAXX/ATRX and mTOR pathway genes are associated with development and progression in pancreatic neuroendocrine tumours. The other changes are in VEGF pathway, Notch pathway, germline mutations in MUTYH, CHEK2, BRCA2, PHLDA3 as well as other genetic alterations. On the other hand, pancreatic neuroendocrine carcinomas share similar genetic alterations with ductal adenocarcinomas, e.g., TP53, RB1 or KRAS. In addition, microRNA and changes in immune microenvironment were noted in PanNENs. Updates on these genetic knowledges contribute to the development of management strategies for patients with PanNENs.

The Genetics and Diagnosis of Pediatric Neurocutaneous Disorders: Neurofibromatosis and Tuberous Sclerosis Complex

Neurofibromatosis (NF) and tuberous sclerosis complex (TSC) are the two most common neurocutaneous disorders, both transmitted as autosomal dominant or, in the case of NF, also as a mosaic condition. The causative genetic mutations in these neurocutaneous disorders can lead to benign skin changes or uninhibited growth and proliferation in multiple organ systems due to the loss of tumor suppression in mitogen-activated protein kinase and mammalian target of rapamycin signaling pathways. Common clinical features in NF include pigmented lesions, known as café au lait patches, neurofibromas, intertriginous freckles (Crowe's sign), and benign fibrous growths, such as hamartomas in multiple organ systems. Common clinical features in TSC include hypopigmented macules, known as ash leaf spots, in addition to neurologic sequelae, such as autism, seizures, and developmental delays. Advances in genetic sequencing technologies have allowed an exponential expansion in the understanding of NF and TSC. Consensus criteria have been established for both diagnoses that can be confirmed in most cases through gene testing. Once diagnosed, the clinical and diagnostic value of disease-specific surveillance include early identification of benign and malignant tumors. Genetic counseling is important for informed reproductive decision-making for patients and at-risk family members. The improvement in understanding of pathways of pathogenic disease development and oncogenesis in both conditions have produced a new series of therapeutic options that can be used to control seizures and tumor growth. Tremendous advances in life expectancy and quality of life are now a reality due to early introduction of seizure control and novel medications. While we lack cures, early institution of interventions, such as seizure control in tuberous sclerosis, appears to be disease-modifying and holds immense promise to offer patients better lives.

Genotype-phenotype correlation of renal lesions in the tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal dominant disease caused by loss-of-function mutations in either of two tumor suppressor genes, TSC1 and TSC2. These mutations lead to the growth of benign tumors and hamartomas in many organs, including those of the central nervous system, the skin, and the kidneys. To investigate the genotype-phenotype correlation, we performed sequence analysis of the TSC1/2 genes using next-generation sequencing. We classified 30 patients with TSC whose pathogenic variants were identified into two groups: those with mutations producing premature termination codons (PTCs) and those with missense mutations. Then, we compared the phenotypes between the two groups. Patients with a PTC were significantly more likely to manifest the major symptoms of the diagnostic criteria than those without a PTC (P = 0.035). The frequencies of subependymal nodules (P = 0.026), cortical tubers (P = 0.026), and renal cysts (P = 0.026) were significantly higher in PTC-containing variants than in cases without a PTC. When the analyses were limited to renal angiomyolipoma (AML) cases with TSC2 mutations, there was no difference in tumor size between cases with and without a PTC. However, the cases with a PTC showed a trend toward disease onset at a younger age and multiple tumors, and bilateral disease was observed in their AML lesions. TSC patients with PTC-producing mutations might potentially manifest more severe TSC phenotypes than those with missense mutations. A larger-scale study with appropriate samples deserves further investigation.

Beyond Protein Synthesis; The Multifaceted Roles of Tuberin in Cell Cycle Regulation

The ability of cells to sense diverse environmental signals, including nutrient availability and conditions of stress, is critical for both prokaryotes and eukaryotes to mount an appropriate physiological response. While there is a great deal known about the different biochemical pathways that can detect and relay information from the environment, how these signals are integrated to control progression through the cell cycle is still an expanding area of research. Over the past three decades the proteins Tuberin, Hamartin and TBC1D7 have emerged as a large protein complex called the Tuberous Sclerosis Complex. This complex can integrate a wide variety of environmental signals to control a host of cell biology events including protein synthesis, cell cycle, protein transport, cell adhesion, autophagy, and cell growth. Worldwide efforts have revealed many molecular pathways which alter Tuberin post-translationally to convey messages to these important pathways, with most of the focus being on the regulation over protein synthesis. Herein we review the literature supporting that the Tuberous Sclerosis Complex plays a critical role in integrating environmental signals with the core cell cycle machinery.

Compendium of causative genes and their encoded proteins for common monogenic disorders

A compendium is presented of inherited monogenic disorders that have a prevalence of >1:20,000 in the human population, along with their causative genes and encoded proteins. "Simple" monogenic diseases are those for which the clinical features are caused by mutations impacting a single gene, usually in a manner that alters the sequence of the encoded protein. Of course, for a given "monogenic disorder", there is sometimes more than one potential disease gene, mutations in any one of which is sufficient to cause phenotypes of that disorder. Disease-causing mutations for monogenic disorders are usually passed on from generation to generation in a Mendelian fashion, and originate from spontaneous (de novo) germline founder mutations. In the past monogenic disorders have often been written off as targets for drug discovery because they sometimes are assumed to be rare disorders, for which the meager projected financial payoff of drug discovery and development has discouraged investment. However, not all monogenic diseases are rare. Here, we report that that currently available data identifies 72 disorders with a prevalence of at least 1 in 20,000 humans. For each, we tabulate the gene(s) for which mutations cause the spectrum of phenotypes associated with that disorder. We also identify the gene and protein that most commonly causes each disease. 34 of these disorders are caused exclusively by mutations in only a single gene and encoded protein.

Brachial and subclavian arteries aneurysms due to tuberous sclerosis complex mechanisms - case report and literature review

INTRODUCTION

Tuberous sclerosis complex (TSC) is a rare autosomal dominant condition characterized by cutaneous, cerebral, and other multiorgan involvement. Aneurysms due to TSC pathogenic mechanism are rarely present, mainly aortic, renal, or intracranial and very few associated with peripheral circulation. A TSC patient, aged 31 years, who developed brachial and subclavian arteries aneurysms is presented. The question of a random association of the aneurysms with TSC versus aneurysms within pathogenic released mammalian target of rapamycin (mTOR) pathway effect was raised.

CASE PRESENTATION

Patient's file, available from the age of six months, was analyzed for demonstration of the TSC diagnosis. Patient was examined, and cerebral magnetic resonance imaging (MRI) was repeated. Surgery and angiographic reports and images were reviewed. Pathology of the aneurysmal wall available from surgery was reexamined and special stainings and immunohistochemistry markers were applied. Genetic characterization of the patient was performed. Definite TSC was diagnosed based on major criteria [ungual fibromas, shagreen patch, cortical tubers, subependymal nodules (SENs), subependymal giant cell astrocytoma (SEGA)], minor criteria (confetti skin lesions, dental enamel pits, gingival fibromas), genetic result showing heterozygous variant in exon 8 of TSC1 gene (c.733C>T-p.Arg245*). Pathology analysis revealed markedly thickened aneurysmal wall due to smooth muscle cells (SMCs) proliferation in media and neoformation vessels with similar characteristics in the aneurysmal wall.

DISCUSSIONS AND CONCLUSIONS

This is a rare case with aneurysms related to TSC, with an exceptional peripheral localization. Pathology exam is the key investigation in demonstrating the TSC-related pathogenic mechanism. A literature review showed 73 TSC cases presenting aneurysms published until now.

An Israeli tuberous sclerosis cohort: the efficacy of different anti-epileptic strategies

AIM

We aimed to describe the experience of a large single-center cohort for the clinical, radiological, and genetic characteristics, as well as to determine the efficacy of different anti-epileptic strategies in children and adults with tuberous sclerosis complex (TSC).

METHODS

We carried out a historical cohort study on 91 TSC patients treated in a single center between 2008 and 2018.

RESULTS

Our cohort comprised 46 males and 45 females, with a median age of 15.6 years at the last follow-up. Mean follow-up time was 2.5 ± 0.75-5.5 years (range 0-9.5 years). Of those tested, a disease-causing mutation was identified in 90% of patients, 53% in TSC2, and 37% in TSC1. Epilepsy prevalence was similar among TSC1 and TSC2 mutated patients. The most common radiological finding were cortical tubers in 95% of patients, while subependymal giant cell astrocytoma (SEGA) were detected in 36% of patients. Notably, infantile spasms (IS) were diagnosed in 29%, with SEGA representing the only finding significantly different in prevalence between those with and without IS (62% vs. 28%, respectively, p = 0.009). Lastly, we did not find any difference in efficacy between three anti-epileptic treatments: Vagus nerve stimulation (VNS), CBD-based products, and the ketogenic diet, all showing approximately 30%-40% response rates.

SIGNIFICANCE

Altogether, we provide a comprehensive description of our experience in treating TSC, which could serve to expand current knowledge of the disease and its treatments.

Risk Factors Associated with Refractory Epilepsy in Patients with Tuberous Sclerosis Complex: A Systematic Review

BACKGROUND

Epilepsy affects 70-90% of patients with tuberous sclerosis complex (TSC). In one-third of them, the seizures become refractory to treatment. Drug-resistant epilepsy (DRE) carries a significant educational, social, cognitive, and economic burden. Therefore, determining risk factors that increase the odds of refractory seizures is needed. We reviewed current data on risk factors associated with DRE in patients with tuberous sclerosis.

METHODS

The review was performed according to the PRISMA guidelines. Embase, Cochrane Library, MEDLINE, and ClinicalTrial.gov databases were searched. Only full-text journal articles on patients with TSC which defined risk factors related to DRE were included.

RESULTS

Twenty articles were identified, with a cohort size between 6 and 1546. Seven studies were prospective. Three factors appear to significantly increase DRE risk: TSC2 mutation, infantile spasms, and a high number of cortical tubers.

CONCLUSIONS

A proper MRI and EEG monitoring, along with genetic testing, and close observation of individuals with early onset of seizures, allow identification of the patients at risk of DRE.

Impaired myelin production due to an intrinsic failure of oligodendrocytes in mTORpathies

AIMS

We aim to evaluate if the myelin pathology observed in epilepsy-associated focal cortical dysplasia type 2B (FCD2B) and-histologically indistinguishable-cortical tubers of tuberous sclerosis complex (TSC) is primarily related to the underlying malformation or constitutes a secondary phenomenon due to the toxic microenvironment created by epileptic seizures. We also aim to investigate the possible beneficial effect of the mTOR pathway regulator everolimus on white matter pathology.

METHODS

Primary mixed glial cell cultures derived from epilepsy surgery specimens of one TSC and seven FCD2B patients were grown on polycaprolactone fibre matrices and analysed using immunofluorescence and electron microscopy. Unaffected white matter from three age-matched epilepsy patients with mild malformations of cortical development (mMCD) and one with FCD3D served as controls. Additionally, TSC2 knock-out was performed using an oligodendroglial cell line. Myelination capacities of nanofibre grown cells in an inflammatory environment after mTOR-inhibitor treatment with everolimus were further investigated.

RESULTS

Reduced oligodendroglial turnover, directly related to a lower myelin content was found in the patients' primary cells. In our culture model of myelination dynamics, primary cells grown under 'inflammatory condition' showed decreased myelination, that was repaired by treatment with everolimus.

CONCLUSIONS

Results obtained in patient-derived primary oligodendroglial and TSC2 knock-out cells suggest that maturation of oligodendroglia and production of a proper myelin sheath seem to be impaired as a result of mTOR pathway disturbance. Hence, oligodendroglial pathology may reflect a more direct effect of the abnormal genetic programme rather than to be an inactive bystander of chronic epilepsy.

Detection of TSC1/TSC2 mosaic variants in patients with cardiac rhabdomyoma and tuberous sclerosis complex by hybrid-capture next-generation sequencing

Background

Fetal cardiac rhabdomyoma (CR) is strongly associated with tuberous sclerosis complex (TSC), which is caused by variants in TSC1 and TSC2. However, in 10%–15% of patients with clinically confirmed TSC, no TSC1/TSC2 variants are identified by panel sequencing or multiplex ligation‐dependent probe amplification (MLPA).

Methods

We analyzed eight fetuses with CR and their families. No TSC1/TSC2 variants had previously been identified for six of these fetuses, and we suspected the other two families of gonadal mosaicism. We performed next‐generation sequencing (NGS) using CR tissue, umbilical cord tissue, and parental blood. All positive results, involving two paternal semen, were verified by droplet digital polymerase chain reaction (ddPCR).

Results

Four fetuses carried low‐level mosaic variants (0.05%–14.89%), and two only exhibited somatic mosaic variants in the CR tissue (15.76% and 37.69%). Two fathers had gonadal mosaicism (9.07% and 4.86%). We identified nine pathogenic variants in eight fetuses, including one fetus with a second‐hit variant.

Conclusion

The fetuses assessed in this study carried low‐level and somatic mosaic variants, and CR tissue from one fetus exhibited a second‐hit variant. Heterozygous gonadal variants can exist in patients with low‐level mosaicism. Combining NGS with ddPCR improves the accuracy of prenatal TSC diagnosis.

Lymphangioleiomyomatosis Association with Underlying Genotype in Patients with Tuberous Sclerosis Complex

Rationale: Lymphangioleiomyomatosis (LAM) is a female-predominant lung disease caused by mutations in the tuberous sclerosis complex (TSC) genes TSC1 and TSC2.Objectives: To examine the association between TSC mutation subtypes and the prevalence of LAM in women with TSC.Methods: Adult women seen at the Cincinnati Children's Hospital Medical Center's TSC clinic were stratified into the following three groups: those with TSC1 mutation, those with TSC2 mutation, and those with no mutation identified (NMI). Individual TSC manifestations were ascertained by blinded review of chest computed tomographic scans (LAM, multifocal micronodular pneumocyte hyperplasia, and sclerotic bone lesions) and chart review (all other manifestations). The association between mutation status and TSC manifestations was assessed by the Wilcoxon rank-sum test.Results: Our cohort consisted of 55 TSC women, including 30/55 (55%) with TSC2, 12/55 (22%) with TSC1, and 13/55 (23%) with NMI. Twenty-three women (42%) had characteristic cysts consistent with LAM, of whom 16 had TSC2 mutations and seven had NMI. The prevalence of LAM was higher in women with TSC2 mutations compared with women with TSC1 mutations (16/29 [55%] vs. 0/12; P = 0.003). Similarly, renal angiomyolipomas were more common in women with TSC2 mutations compared with women with TSC1 mutations (29/30 [97%] vs. 6/12 [50%]; P = 0.01). There was no association between TSC mutation subtype and the presence of multifocal micronodular pneumocyte hyperplasia, sclerotic bone lesions, and skin or brain involvement. Serum VEGF-D (vascular endothelial growth factor-D) concentrations (median [95% confidence interval]) tended to be higher in patients harboring TSC2 mutations compared with patients with TSC1 mutations (725 pg/ml [612-1,317] vs. 331 pg/ml [284-406]; P = 0.03) and in patients with LAM compared with patients without LAM (725 pg/ml [563-1,609] vs. 429 pg/ml [357-773]; P = 0.02).Conclusions: LAM and angiomyolipomas are more common in women with TSC harboring TSC2 mutations compared with women with TSC1 mutations. Serum VEGF-D is a useful biomarker to suggest the presence of LAM in women with TSC.

Alterations in resting-state functional connectivity in pediatric patients with tuberous sclerosis complex

Objective

To investigate resting‐state functional connectivity (FC) in pediatric patients with tuberous sclerosis complex and intractable epilepsy requiring surgery.

Methods

Resting‐state functional MRI was utilized to investigate functional connectivity in 13 pediatric patients with tuberous sclerosis complex (TSC) and intractable epilepsy requiring surgery.

Results

The majority of patients demonstrated a resting‐state network architecture similar to those reported in healthy individuals. However, preoperative differences were evident between patients with high versus low tuber burden, as well as those with good versus poor neurodevelopmental outcomes, most notably in the cingulo‐opercular and visual resting‐state networks. One patient with high tuber burden and poor preoperative development and seizure control had nearly normal development and seizure resolution after surgery. This was accompanied by significant improvement in resting‐state network architecture just one day postoperatively.

Significance

Although many patients with tuberous sclerosis complex and medically refractory epilepsy demonstrate functional connectivity patterns similar to healthy children, relationships within and between RSNs demonstrate clear differences in patients with higher tuber burden and worse outcomes. Improvements in resting‐state network organization postoperatively may be related to epilepsy surgery outcomes, providing candidate biomarkers for clinical management in this high‐risk population.

Renal neoplasms in tuberous sclerosis mice are neurocristopathies

Tuberous sclerosis (TS) is a rare disorder exhibiting multi-systemic benign neoplasms. We hypothesized the origin of TS neoplastic cells derived from the neural crest given the heterogeneous ecto-mesenchymal phenotype of the most common TS neoplasms. To test this hypothesis, we employed Cre-loxP lineage tracing of myelin protein zero (Mpz)-expressing neural crest cells (NCCs) in spontaneously developing renal tumors of Tsc2 +/- /Mpz(Cre)/TdT fl/fl reporter mice. In these mice, ectopic renal tumor onset was detected at 4 months of age increasing in volume by 16 months of age with concomitant increase in the subpopulation of tdTomato+ NCCs from 0% to 6.45% of the total number of renal tumor cells. Our results suggest that Tsc2 +/- mouse renal tumors arise from domiciled proliferative progenitor cell populations of neural crest origin that co-opt tumorigenesis due to mutations in Tsc2 loci. Targeting neural crest antigenic determinants will provide a potential alternative therapeutic approach for TS pathogenesis.

Brain Symptoms of Tuberous Sclerosis Complex: Pathogenesis and Treatment

The mammalian target of the rapamycin (mTOR) system plays multiple, important roles in the brain, regulating both morphology, such as cellular size, shape, and position, and function, such as learning, memory, and social interaction. Tuberous sclerosis complex (TSC) is a congenital disorder caused by a defective suppressor of the mTOR system, the TSC1/TSC2 complex. Almost all brain symptoms of TSC are manifestations of an excessive activity of the mTOR system. Many children with TSC are afflicted by intractable epilepsy, intellectual disability, and/or autism. In the brains of infants with TSC, a vicious cycle of epileptic encephalopathy is formed by mTOR hyperactivity, abnormal synaptic structure/function, and excessive epileptic discharges, further worsening epilepsy and intellectual/behavioral disorders. Molecular target therapy with mTOR inhibitors has recently been proved to be efficacious for epilepsy in human TSC patients, and for autism in TSC model mice, indicating the possibility for pharmacological treatment of developmental synaptic disorders.

TSC1 and TSC2: Tuberous Sclerosis Complex and Its Related Epilepsy Phenotype

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by a multisystemic involvement. In TSC, reduced function of TSC1 and TSC2 genes products (hamartin and tuberin, respectively) leads to an hyperactivation of the mechanistic target of rapamycin (mTOR) pathway and to a consequent cell growth dysregulation. In TSC patients, neurological and neuropsychiatric manifestations, especially epilepsy and neuropsychiatric comorbidities such as autism or intellectual disability, represent the most disabling features. In particular, epilepsy occurrs up to 80% of patients, is often drug resistant and is frequently associated with neurological impairment. Due to the burden of this morbidity, different treatment strategies have been proposed with the purpose to make patients epilepsy free, such as the use of different antiepileptic drugs like vigabatrin, carbamazepine, valproic acid, and levetiracetam. More recently, a mTOR inhibitor (i.e. everolimus) has showed promising results in terms of seizures reduction.

Current concepts on ocular vascular abnormalities in the phakomatoses

BACKGROUND

Neurofibromatosis, Von Hippel Lindau disease, and tuberous sclerosis complex are classified under the term phakomatoses. They are characterized by ocular vascular abnormalities such as vascular tortuosity, corkscrew retinal vessel configuration, moyamoya-like aspect, microaneurysms, hemangioblastomas, and focal sheathing of retinal arteries, possibly due to abnormal formation, migration, and differentiation of neural crest cells. These alterations can be the first sign or the hallmark of disease and can be related to vasoproliferative tumors.

PURPOSE

Novel imaging technologies in ophthalmology, such as near-infrared reflectances and spectral domain optical coherence tomography, have improved our knowledge in the diagnosis of these pathologies. Previously undetected macular vascular alterations have been reported in phakomatoses using optical coherence tomography angiography. This review will summarize the ophthalmic vascular abnormalities and novel imaging methods in the phakomatoses.

CONCLUSION

Active research is being led into the ophthalmic management of these conditions and their complications, and owing to elevated vascular endothelial growth factor production from hemangioblastoma, hamartoma, and retinal vascular proliferative tumors, increasing interest in this line of therapy has been conducted although research is still ongoing in this area.

Myelin Pathology Beyond White Matter in Tuberous Sclerosis Complex (TSC) Cortical Tubers

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.

The Correlation Between Tuberous Sclerosis Complex Genotype and Renal Angiomyolipoma Phenotype

Tuberous sclerosis complex (TSC) is a rare multisystem autosomal dominant genetic disease that occurs between 1 in 6,000 and 1 in 10,000 live births. Additionally, renal angiomyolipoma is the most common form of renal disease in patients affected by TSC. Although a genetic mutation analysis of TSC is not rare, the correlation between the TSC gene mutation and renal angiomyolipoma phenotype is poorly understood. This study aims to analyze the mutation sites in 261 types of selected TSC patients. The results reveal that: (1) female patients develop more renal angiomyolipoma than male patients [p = 0.008, OR = 2.474, 95%CI (1.258–4.864)]; (2). The missense mutation of TSC1 led to a higher risk of renal angiomyolipoma [p < 0.01, OR = 15, 95%CI (2.859–78.691)], and in contrast, showed a reduced risk in patients with frameshift mutation [p = 0.03, OR = 0.252, 95%CI (0.07–0.912)]; (3). Patients with TSC2 mutations in the transcription activation domain 1 coding genes, had increased renal angiomyolipoma [p = 0.019, OR = 3.519, 95%CI (1.226–10.101)]. Therefore, our genotype-phenotype correlation study might shed light on the early monitoring and evaluation of renal angiomyolipoma in TSC patients.

Successful endovascular treatment of spontaneous intrarenal pseudoaneurysm in a case of tuberous sclerosis

Tuberous sclerosis is a complex disorder which has multisystem involvement and varied clinical manifestations. Almost half of the patients have associated angiomyolipoma which contains fat, vascular and smooth muscle components. Spontaneous pseudoaneurysm formation is a complication of angiomyolipoma. Here we present a case of a female child presenting with hematuria who after thorough clinical and radiological investigations was diagnosed as a case of tuberous sclerosis with right intrarenal pseudoaneurysm. She was successfully treated with endovascular coil embolization.

Three-dimensional digital PCR through light-sheet imaging of optically cleared emulsion

The realization of the vast potential of digital PCR (dPCR) to provide extremely accurate and sensitive measurements in the clinical setting has thus far been hindered by challenges such as assay robustness and high costs. Here we introduce a lossless and contamination-free dPCR technology, termed CLEAR-dPCR, which addresses these challenges by completing the dPCR sample preparation, PCR, and readout all in one tube. Optical clearing of the droplet dPCR emulsion was combined with emerging light-sheet fluorescence microscopy, to acquire a three-dimensional (3D) image of a half million droplets sealed in a tube in seconds. CLEAR-dPCR provides ultrahigh-throughput readout results in situ and fundamentally eliminates the possibility of either sample loss or contamination. This approach exhibits improved accuracy over existing dPCR platforms and enables a greatly increased dynamic range to be comparable to that of real-time quantitative PCR.

Mutation Spectrum of Tuberous Sclerosis Complex Patients in Indian Population

Tuberous sclerosis complex (TSC) is a multiorgan disorder characterized by formation of hamartomas and broad phenotypic spectrum including seizures, mental retardation, renal dysfunction, skin manifestations and brain tubers. It is inherited in an autosomal dominant pattern, caused due to mutation in either TSC1 or TSC2 genes. Seizures are one of the major presenting symptoms of TSC that helps in early diagnosis. The present study describes the mutation spectrum in TSC1 and TSC2 genes in TSC patients and their association with neurocognitive-behavioral phenotypes. Ninety-eight TSC patients were enrolled for TSC genetic testing after detailed clinical and neurobehavioral assessment. Large genomic rearrangement testing was performed by multiplex ligation-dependent probe amplification (MLPA) technique for all cases and Sanger sequencing was performed for MLPA negative cases. Large rearrangements were identified in approximately 1% in TSC1 and 14.3% in TSC2 genes. The present study observed the presence of duplications in two (2%) cases, both involving TSC2/PKD1 contiguous genes which to the best of our knowledge is reported for the first time. 8.1% of small variants were identified in the TSC1 gene and 85.7% in TSC2 gene, out of which 23 were novel variations and no variants were found in six (6.1%) cases. This study provides a representative picture of the distribution of variants in the TSC1 and TSC2 genes in Indian population along with the detailed assessment of neurological symptoms. This is the largest cohort study from India providing an overview of comprehensive clinical and molecular spectrum.

Renal Manifestations of Tuberous Sclerosis Complex

Tuberous sclerosis complex (TSC) is a genetic condition caused by a mutation in either the TSC1 or TSC2 gene. Disruption of either of these genes leads to impaired production of hamartin or tuberin proteins, leading to the manifestation of skin lesions, tumors, and seizures. TSC can manifest in multiple organ systems with the cutaneous and renal systems being the most commonly affected. These manifestations can secondarily lead to the development of hypertension, chronic kidney disease, and neurocognitive declines. The renal pathologies most commonly seen in TSC are angiomyolipoma, renal cysts, and less commonly, oncocytomas. In this review, we highlight the current understanding on the renal manifestations of TSC along with current diagnosis and treatment guidelines.

Recombinant Tumor Suppressor TSC1 Differentially Interacts with Escherichia coli DnaK and Human HSP70

Tuberous sclerosis complex (TSC) is a neurological syndrome manifested by non-cancerous tumors in several organs. Mutations in either TSC1 or TSC2 tumor suppressor gene cause the disease. In the cell, TSC1 is known to form a heterodimer with TSC2 because of which an active complex is formed that negatively regulates the mTORC1 activity during cellular stress. Hence, mutation in TSC1 or TSC2 is manifested by excess proliferation of the cells leading to the development of numerous benign tumors. The TSC1 and TSC2 complex is known to interact with several protein-binding partners. One such significant interaction of this complex is with the molecular chaperone HSP70. The role of TSC1 in that interaction is still elusive. Here, we have expressed and purified TSC1 (302-420 residues) in a bacterial expression system and have shown that this region directly interacts with HSP70. We have shown that TSC1 increases the ATPase activity of Escherichia coli DnaK, a HSP70 homologue. On the contrary, TSC1 was found to show inhibitory activity toward human HSP70. Our result suggests that TSC1 (302-420 aa) shows differential interaction between the HSP70 homologues. This points toward the evolutionary significance of chaperoning system and the importance of eukaryotic tetratricopeptide repeat domain interaction motif -EEVD. Our study shows the evidence that TSC1 interacts with HSP70 and has a role to play in the chaperoning activity to maintain cellular homeostasis.

Mutational analysis of TSC1 and TSC2 in Danish patients with tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by hamartomas in the skin and other organs, including brain, heart, lung, kidney and bones. TSC is caused by mutations in TSC1 and TSC2. Here, we present the TSC1 and TSC2 variants identified in 168 Danish individuals out of a cohort of 327 individuals suspected of TSC. A total of 137 predicted pathogenic or likely pathogenic variants were identified: 33 different TSC1 variants in 42 patients, and 104 different TSC2 variants in 126 patients. In 40 cases (24%), the identified predicted pathogenic variant had not been described previously. In total, 33 novel variants in TSC2 and 7 novel variants in TSC1 were identified. To assist in the classification of 11 TSC2 variants, we investigated the effects of these variants in an in vitro functional assay. Based on the functional results, as well as population and genetic data, we classified 8 variants as likely to be pathogenic and 3 as likely to be benign.

High Mobility Group AT-Hook 2 (HMGA2) Oncogenicity in Mesenchymal and Epithelial Neoplasia

High mobility group AT-hook 2 (HMGA2) has been associated with increased cell proliferation and cell cycle dysregulation, leading to the ontogeny of varied tumor types and their metastatic potentials, a frequently used index of disease prognosis. In this review, we deepen our understanding of HMGA2 pathogenicity by exploring the mechanisms by which HMGA2 misexpression and ectopic expression induces mesenchymal and epithelial tumorigenesis respectively and distinguish the pathogenesis of benign from malignant mesenchymal tumors. Importantly, we highlight the regulatory role of let-7 microRNA family of tumor suppressors in determining HMGA2 misexpression events leading to tumor pathogenesis and focused on possible mechanisms by which HMGA2 could propagate lymphangioleiomyomatosis (LAM), benign mesenchymal tumors of the lungs. Lastly, we discuss potential therapeutic strategies for epithelial and mesenchymal tumorigenesis based on targeting the HMGA2 signaling pathway.

First comprehensive TSC1/TSC2 mutational analysis in Mexican patients with Tuberous Sclerosis Complex reveals numerous novel pathogenic variants

The aim of this study was to improve knowledge of the mutational spectrum causing tuberous sclerosis complex (TSC) in a sample of Mexican patients, given the limited information available regarding this disease in Mexico and Latin America. Four different molecular techniques were implemented to identify from single nucleotide variants to large rearrangements in the TSC1 and TSC2 genes of 66 unrelated Mexican-descent patients that clinically fulfilled the criteria for a definitive TSC diagnosis. The mutation detection rate was 94%, TSC2 pathogenic variants (PV) prevailed over TSC1 PV (77% vs. 23%) and a recurrent mutation site (hotspot) was observed in TSC1 exon 15. Interestingly, 40% of the identified mutations had not been previously reported. The wide range of novels PV made it difficult to establish any genotype-phenotype correlation, but most of the PV conditioned neurological involvement (intellectual disability and epilepsy). Our 3D protein modeling of two variants classified as likely pathogenic demonstrated that they could alter the structure and function of the hamartin (TSC1) or tuberin (TSC2) proteins. Molecular analyses of parents and first-degree affected family members of the index cases enabled us to distinguish familial (18%) from sporadic (82%) cases and to identify one case of apparent gonadal mosaicism.