Severity of manifestations in tuberous sclerosis complex in relation to genotype

Heterozygous loss of TSC2 alters p53 signaling and human stem cell reprogramming

Tuberous sclerosis complex (TSC) is a pediatric disorder of dysregulated growth and differentiation caused by loss of function mutations in either the TSC1 or TSC2 genes, which regulate mTOR kinase activity. To study aberrations of early development in TSC, we generated induced pluripotent stem cells using dermal fibroblasts obtained from patients with TSC. During validation, we found that stem cells generated from TSC patients had a very high rate of integration of the reprogramming plasmid containing a shRNA against TP53. We also found that loss of one allele of TSC2 in human fibroblasts is sufficient to increase p53 levels and impair stem cell reprogramming. Increased p53 was also observed in TSC2 heterozygous and homozygous mutant human stem cells, suggesting that the interactions between TSC2 and p53 are consistent across cell types and gene dosage. These results support important contributions of TSC2 heterozygous and homozygous mutant cells to the pathogenesis of TSC and the important role of p53 during reprogramming.

Clinical report: a rare co-occurrence of tuberous sclerosis complex and Rett syndrome in a girl with mental retardation, epilepsy and autism

Introduction.There are some genetic disorders with combination of mental retardation, epilepsy and autism in which the abnormal mammalian Target of Rapamycin (m-TOR) signaling is implicated. The most important of them is tuberous sclerosis complex (TSC), but the disturbances of the m-TOR pathway can also be detected in Rett syndrome (RS), Fragile X syndrome and Down syndrome. We describe the rare case of co-occurrence of TSC and RS.

Case study.The female child was born at term by normal delivery after a non-complicated pregnancy. Family history was negative for epilepsy and mental retardation. The neonatal period was uneventful and psychomotor development was normal before the child became 1.5 years old. At the age of 18 months the girl developed hand-wringing stereotypes, facial hypotonia, ataxia and gait apraxia. She lost eye-to-eye contact and verbal contact with relatives, and became indifferent to the surrounding environment. When she was 2 years old, focal adversive seizures started which were readily controlled with carbamazepine. Cerebral cortical and subcortical tubers, cerebral white-matter radial migration lines and subependymal nodules on brain MRI together with hypomelanotic macules suggested the presence of TSC. Diagnosis was confirmed at age of 3 years by a heterozygous mutation c.5161-2A>G inTSC2gene on chromosome 16p13. But the rude regression of psychomotor development and speech, autistic features alongside with characteristic hand-wringing stereotypes were unexplained until at age of 4.5 years RS was diagnosed by finding a heterozygous missense mutation in exon 4 of theMECP2gene c.455C>T, resulting in a P152R substitution in the methyl-binding domain of the protein. At age of 5 the patient is not able to walk independently and has no expressive speech, she is autistic, has ataxia, limb rigidity, hyperreflexia, lack of purposeful hand movements, verbal and motor stereotypies.

Discussion.The presence of two mutations (one characteristic forTSC2and one – characteristic for RS) significantly worsened the developmental and motor delay and autistic features in our patient. Dysregulation of m-TOR way is well established in TSC and recently described in RS, Down syndrome and Fragile X syndrome.

Predictors of Drug-Resistant Epilepsy in Tuberous Sclerosis Complex

Utilizing the multicenter TSC (tuberous sclerosis complex) Natural History Database including 2034 subjects, this study aimed to identify predictors of drug-resistant epilepsy in TSC. Basic epilepsy data were available for 1965 individuals in the database. Supplemental data were further collected from 1546 of these subjects through directed site queries, addressing additional epilepsy characteristics including the presence of drug-resistant epilepsy, therapies trialed, and outcomes of specific therapies. Epilepsy was reported in 86.4% of individuals with TSC. Infantile spasms were reported in 45.2% of individuals and focal seizures were reported in 84.4% of individuals. In those with focal epilepsy, drug resistance was reported in 59.6%, with focal seizure onset prior to age 1 year (odds ratio [OR] 1.9, confidence interval [CI] 1.4-2.5, P < .001), infantile spasms (OR 2.0, CI 1.5-2.5, P < 0.001), and infantile spasms incompletely responsive to therapy (OR 47.6, CI 6.7-333.3, P < 0.001) being associated with an increased likelihood of drug resistance.

Diffusion tensor imaging and magnetic resonance spectroscopy in a patient with adult onset tuberous sclerosis complex

Tuberous sclerosis complex (TSC) 1 or TSC2 is mutated in most TSC patients. TSC2 mutations are more frequently associated with worse outcomes, earlier age at seizure onset, more severe intellectual disability, and higher tuber load than TSC1. The degree of white matter involvement is thought to be associated with the severity of neurological impairment. At present, genotype-phenotype correlations and relationship between tuber burden and neurological disability in TSC are debatable. We presented a 43-year-old patient with TSC2 mutation, whose symptom was only incomplete quadrantic visual field deficit in spite of multiple brain tubers. The visual field deficit was thought to be due to a small lesion in the upper medial part of the optic radiation revealed by diffusion tensor imaging. Her brain tubers showed normal findings in magnetic resonance spectroscopy. Our case suggested that neurological and neuropsychiatric manifestations of TSC are affected by the quality rather than number of the lesions. In addition, MRS may be useful to identify the correlation between brain tubers and neurological disability in TSC patients.

TSC2 c.1864C>T variant associated with mild cases of tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal dominantly inherited disorder with variable expressivity associated with hamartomatous tumors, abnormalities of the skin, and neurologic problems including seizures, intellectual disability, and autism. TSC is caused by pathogenic variants in either TSC1 or TSC2. In general, TSC2 pathogenic variants are associated with a more severe phenotype than TSC1 pathogenic variants. Here, we report a pathogenic TSC2 variant, c.1864C>T, p.(Arg622Trp), associated with a mild phenotype, with most carriers meeting fewer than two major clinical diagnostic criteria for TSC. This finding has significant implications for counseling patients regarding prognosis. More patient data are required before changing the surveillance recommendations for patients with the reported variant. However, consideration should be given to tailoring surveillance recommendations for all pathogenic TSC1 and TSC2 variants with documented milder clinical sequelae. © 2017 Wiley Periodicals, Inc.

Molecular analysis of TSC1 and TSC2 genes and phenotypic correlations in Brazilian families with tuberous sclerosis

Tuberous sclerosis complex (TSC) is an autosomal dominant multisystem disorder characterized by the development of multiple hamartomas in many organs and tissues. It occurs due to inactivating mutations in either of the two genes, TSC1 and TSC2, following a second hit in a tumor suppressor gene in most hamartomas. Comprehensive screening for mutations in both the TSC1 and TSC2 loci has been performed in several cohorts of patients and a broad spectrum of pathogenic mutations have been described. In Brazil, there is no data regarding incidence and prevalence of tuberous sclerosis and mutations in TSC1 and TSC2. We analyzed both genes in 53 patients with high suspicion of tuberous sclerosis using multiplex-ligation dependent probe amplification and a customized next generation sequencing panel. Confirmation of all variants was done by the Sanger method. We identified 50 distinct variants in 47 (89%) of the patients. Five were large rearrangements and 45 were point mutations. The symptoms presented by our series of patients were not different between male and female individuals, except for the more common occurrence of shagreen patch in women (p = 0.028). In our series, consistent with other studies, TSC2 mutations were associated with a more severe phenotypic spectrum than TSC1 mutations. This is the first study that sought to characterize the molecular spectrum of Brazilian individuals with tuberous sclerosis.

The genomic landscape of tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is a rare genetic disease causing multisystem growth of benign tumours and other hamartomatous lesions, which leads to diverse and debilitating clinical symptoms. Patients are born with TSC1 or TSC2 mutations, and somatic inactivation of wild-type alleles drives MTOR activation; however, second hits to TSC1/TSC2 are not always observed. Here, we present the genomic landscape of TSC hamartomas. We determine that TSC lesions contain a low somatic mutational burden relative to carcinomas, a subset feature large-scale chromosomal aberrations, and highly conserved molecular signatures for each type exist. Analysis of the molecular signatures coupled with computational approaches reveals unique aspects of cellular heterogeneity and cell origin. Using immune data sets, we identify significant neuroinflammation in TSC-associated brain tumours. Taken together, this molecular catalogue of TSC serves as a resource into the origin of these hamartomas and provides a framework that unifies genomic and transcriptomic dimensions for complex tumours.

TSC1 and TSC2 gene mutations and their implications for treatment in Tuberous Sclerosis Complex: a review

Tuberous sclerosis complex is an autosomal dominant disorder characterized by skin manifestations and formation of multiple tumors in different organs, mainly in the central nervous system. Tuberous sclerosis is caused by the mutation of one of two tumor suppressor genes, TSC1 or TSC2. Currently, the development of novel techniques and great advances in high-throughput genetic analysis made mutation screening of the TSC1 and TSC2 genes more widely available. Extensive studies of the TSC1 and TSC2 genes in patients with TSC worldwide have revealed a wide spectrum of mutations. Consequently, the discovery of the underlying genetic defects in TSC has furthered our understanding of this complex genetic disorder, and genotype-phenotype correlations are becoming possible, although there are still only a few clearly established correlations. This review focuses on the main symptoms and genetic alterations described in TSC patients from 13 countries in three continents, as well as on genotype-phenotype correlations established to date. The determination of genotype-phenotype correlations may contribute to the establishment of successful personalized treatment for TSC.

Genetics of tuberous sclerosis complex: implications for clinical practice

Tuberous sclerosis complex (TSC) is a multisystem disorder that results from heterozygous mutations in either TSC1 or TSC2. The primary organ systems that are affected include the brain, skin, lung, kidney, and heart, all with variable frequency, penetrance, and severity. Neurological features include epilepsy, autism, and intellectual disability. There are more than 1,500 known pathogenic variants for TSC1 and TSC2, including deletion, nonsense, and missense mutations, and all pathogenic mutations are inactivating, leading to loss of function effects on the encoded proteins TSC1 and TSC2. These proteins form a complex to constitutively inhibit mechanistic target of rapamycin (mTOR) signaling cascade, and as a consequence, mTOR signaling is constitutively active within all TSC-associated lesions. The mTOR inhibitors rapamycin (sirolimus) and everolimus have been shown to reduce the size of renal and brain lesions and improve pulmonary function in TSC, and these compounds may also decrease seizure frequency. The clinical application of mTOR inhibitors in TSC has provided one of the first examples of precision medicine in a neurodevelopmental disorder.

Systemic disease manifestations associated with epilepsy in tuberous sclerosis complex

OBJECTIVE

Epilepsy is one of the most disabling symptoms of tuberous sclerosis complex (TSC) and is a leading cause of morbidity and mortality in affected individuals. The relationship between systemic disease manifestations and the presence of epilepsy has not been thoroughly investigated. This study utilizes a multicenter TSC Natural History Database including 1,816 individuals to test the hypothesis that systemic disease manifestations of TSC are associated with epilepsy.

METHODS

Univariate analysis was used to identify patient characteristics (e.g., age, gender, race, and TSC mutation status) associated with the presence of epilepsy. Individual logistic regression models were built to examine the association between epilepsy and each candidate systemic or neurologic disease variable, controlling for the patient characteristics found to be significant on univariate analysis. Finally, a multivariable logistic regression model was constructed, using the variables found to be significant on the individual analyses as well as the patient characteristics that were significant on univariate analysis.

RESULTS

Nearly 88% of our cohort had a history of epilepsy. After adjusting for age, gender, and TSC mutation status, multiple systemic disease manifestations including cardiac rhabdomyomas (odds ratio [OR] 2.3, 95% confidence interval [CI] 1.3-3.9, p = 0.002), retinal hamartomas (OR 2.1, CI 1.0-4.3, p = 0.04), renal cysts (OR 2.1, CI 1.3-3.4, p = 0.002), renal angiomyolipomas (OR 3.0, CI 1.8-5.1, p < 0.001), shagreen patches (OR 1.7, CI 1.0-2.7, p = 0.04), and facial angiofibromas (OR 1.7, CI 1.1-2.9, p = 0.03) were associated with a higher likelihood of epilepsy. In the multivariable logistic regression model, cardiac rhabdomyomas (OR 1.9, CI 1.0-3.5, p = 0.04) remained significantly associated with the presence of epilepsy.

SIGNIFICANCE

The identification of systemic disease manifestations such as cardiac rhabdomyomas that confer a higher risk of epilepsy development in TSC could contribute to disease prognostication and assist in the identification of individuals who may receive maximal benefit from potentially novel, targeted, preventative therapies.

Genotype and brain pathology phenotype in children with tuberous sclerosis complex

Structural brain malformations associated with Tuberous Sclerosis Complex (TSC) are related to the severity of the clinical symptoms and can be visualized by magnetic resonance imaging (MRI). Tuberous Sclerosis Complex is caused by inactivating TSC1 or TSC2 mutations. We investigated associations between TSC brain pathology and different inactivating TSC1 and TSC2 variants, and examined the potential prognostic value of subdivision of TSC2 variants based on their predicted effects on TSC2 expression. We performed genotype-phenotype associations of TSC-related brain pathology on a cohort of 64 children aged 1.4-17.9 years. Brain abnormalities were assessed using MRI. Individuals were grouped into those with an inactivating TSC1 variant and those with an inactivating TSC2 variant. The TSC2 group was subdivided into changes predicted to result in TSC2 protein expression (TSC2p) and changes predicted to prevent expression (TSC2x). The TSC2 group was associated with more and larger tubers, more radial migration lines, and more subependymal nodules than the TSC1 group. Subependymal nodules were also more likely to be calcified. Subdivision of the TSC2 group did not reveal additional, substantial differences, except for a larger number of tubers in the temporal lobe and a larger fraction of cystic tubers in the TSC2x subgroup. The severity of TSC-related brain pathology was related to the presence of an inactivating TSC2 variant. Although larger studies might find specific TSC2 variants that have prognostic value, in our cohort, subdivision of the TSC2 group did not lead to better prediction.

Tuberous sclerosis complex: Five new things

Purpose of review

Tuberous sclerosis complex (TSC) is a variably expressed neurocutaneous genetic disorder characterized by hamartomatous growths in multiple organ systems. Neurologic involvement often confers the most severe symptoms, and can include epilepsy, increased intracranial pressure from hydrocephalus, intellectual deficits, and autism. The purpose of this review is to provide a neurologically focused update in the diagnosis and treatment of these complications in patients with TSC.

Recent findings

We highlight 5 new areas of understanding in TSC: the neurobiology of TSC and its translation into clinical practice, vigabatrin in the treatment of infantile spasms, the role of tubers and epilepsy surgery, the treatment of subependymal giant cell astrocytomas, and TSC-related neuropsychiatric disorders.

Summary

These recent advances in diagnosis and treatment give our patients with TSC and their families hope for the future for improved care and possible preventive cures, to the end goal of improving quality of life.

Metabolic, endocrine, and other genetic disorders

Metabolic, endocrine, and genetic diseases of the brain include a very large array of disorders caused by a wide range of underlying abnormalities and involving a variety of brain structures. Often these disorders manifest as recognizable, though sometimes overlapping, patterns on neuroimaging studies that may enable a diagnosis based on imaging or may alternatively provide enough clues to direct further diagnostic evaluation. The diagnostic workup can include various biochemical laboratory or genetic studies. In this chapter, after a brief review of normal white-matter development, we will describe a variety of leukodystrophies resulting from metabolic disorders involving the brain, including mitochondrial and respiratory chain diseases. We will then describe various acidurias, urea cycle disorders, disorders related to copper and iron metabolism, and disorders of ganglioside and mucopolysaccharide metabolism. Lastly, various other hypomyelinating and dysmyelinating leukodystrophies, including vanishing white-matter disease, megalencephalic leukoencephalopathy with subcortical cysts, and oculocerebrorenal syndrome will be presented. In the following section on endocrine disorders, we will examine various disorders of the hypothalamic-pituitary axis, including developmental, inflammatory, and neoplastic diseases. Neonatal hypoglycemia will also be briefly reviewed. In the final section, we will review a few of the common genetic phakomatoses. Throughout the text, both imaging and brief clinical features of the various disorders will be discussed.

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.

Cerebellar Development and Autism Spectrum Disorder in Tuberous Sclerosis Complex

Approximately 50% of patients with the genetic disease tuberous sclerosis complex present with autism spectrum disorder. Although a number of studies have investigated the link between autism and tuberous sclerosis complex, the etiology of autism spectrum disorder in these patients remains unclear. Abnormal cerebellar function during critical phases of development could disrupt functional processes in the brain, leading to development of autistic features. Accordingly, the authors review the potential role of cerebellar dysfunction in the pathogenesis of autism spectrum disorder in tuberous sclerosis complex. The authors also introduce conditional knockout mouse models of Tsc1 and Tsc2 that link cerebellar circuitry to the development of autistic-like features. Taken together, these preclinical and clinical investigations indicate the cerebellum has a profound regulatory role during development of social communication and repetitive behaviors.