Phenotypic variation of tuberous sclerosis in a single extended kindred

A large deletion in TSC2 causes tuberous sclerosis complex by dysregulating PI3K/AKT/mTOR signaling pathway

BACKGROUND/AIM

Tuberous sclerosis complex (TSC) is a multi-system syndrome caused by loss-of-function mutation in TSC1 or TSC2. Most TSC patients present with cardiac rhabdomyoma or cortical tubers during fetal life, and the symptoms are not uniform as their age. The gene products of TSC1/2 are components of the TSC protein complex and are important role in the PI3K/AKT/mTOR (PAM) signaling pathway. Based on three members of a family with variable expressivity, the purpose of this study was to clarify the clinical features of TSC in different age groups and to analyze the genetic characteristics of TSC2 gene.

METHODS

Clinical exome sequencing and co-segregation were used to identify a three-generation family with four affected individuals. HEK-293T cell model was constructed for subsequent experiments. Quantitative RT-PCR, western blotting, and subcellular localization were used to analyze the expression effect of TSC2 mutation. CCK-8 assay, wound healing assay, and cell cycle analysis were used to analyze the function effect of TSC2 mutation.

RESULT

We identified a TSC family with heterozygous deletion of exon 4 in TSC2 by clinical exon sequencing. Sanger sequencing indicated that the affected individuals have 2541-bp deletion that encompassed exon 4 and adjacent introns. Deletion of exon 4 decreased the TSC2 mRNA and protein levels in HEK-293T cells, and activated the PI3K/AKT/mTOR pathway, thereby altering the cell cycle and promoting cell proliferation and migration.

CONCLUSION

We confirmed the pathogenicity of the large deletion in TSC2 in a three- generations family.. Deletion of exon 4 of TSC2 affected cell proliferation, migration, and cell cycle via abnormal activation of the PAM pathway. This study evaluated the pathogenic effect of deletion of exon 4 of TSC2 and investigated the underlying mechanism.

Systematic Review: Emotion Dysregulation in Syndromic Causes of Intellectual and Developmental Disabilities

OBJECTIVE

To summarize the current state of the literature regarding emotion dysregulation (ED) in syndromic intellectual disabilities (S-IDs) in 6 of the most common forms of S-IDs-Down syndrome, fragile X syndrome (FXS), tuberous sclerosis complex, Williams syndrome, Prader-Willi syndrome, and Angelman syndrome-and to determine future research directions for identification and treatment of ED.

METHOD

PubMed bibliographic database was searched from date of inception to May 2021. PRISMA 2020 guidelines were followed with the flowchart, table of included studies, list of excluded studies, and checklist provided. Filters applied included human research and English. Only original research articles were included in the final set, but review articles were used to identify secondary citations of primary studies. All articles were reviewed for appropriateness by 2 authors and summarized. Inclusion criteria were met by 145 articles (Down syndrome = 29, FXS = 55, tuberous sclerosis complex = 11, Williams syndrome = 18, Prader-Willi syndrome = 24, Angelman syndrome = 8).

RESULTS

Each syndrome review was summarized separately and further subdivided into articles related to underlying neurobiology, behaviors associated with ED, assessment, and targeted intervention. FXS had the most thorough research base, followed by Down syndrome and Prader-Willi syndrome, with the other syndromes having more limited available research. Very limited research was available regarding intervention for all disorders except FXS.

CONCLUSION

Core underlying characteristics of S-IDs appear to place youth at higher risk for ED, but further research is needed to better assess and treat ED in S-IDs. Future studies should have a standard assessment measure of ED, such as the Emotion Dysregulation Inventory, and explore adapting established curricula for ED from the neurotypical and autism spectrum disorder fields.

Dermatological and genetic data in tuberous sclerosis: A prospective single-center study of 38 patients

BACKGROUND

Tuberous sclerosis complex (TSC) is a genetic disorder involving the TSC1 or TSC2 gene. Skin signs are prominent, but dermatological data are scarce. This study aims to describe the cutaneous signs of TSC with the genotype.

METHODS

We studied the dermatological characteristics of 38 patients with TSC at the University Hospital of Montpellier. We collected details of genotypic features.

RESULTS

All the patients presented at least one cutaneous sign. The dermatological examination alone was sufficient to establish a definite diagnosis of TSC based on the diagnostic criteria for 34/38 patients. No association was found between cutaneous signs and the presence of a TSC1 or TSC2 mutation. We noted skin signs that were poorly described in the disease, namely epidermal nevus in 3 patients, vascular malformation in 2 patients, and keratosis pilaris in 9 patients.

DISCUSSION

While several studies demonstrate a more severe neurological phenotype in TSC2 mutated patients, skin expression does not appear to differ according to the mutated gene. Further case reports and molecular genetic studies are needed to determine the link between epidermal nevus, vascular malformations, keratosis pilaris and TSC.

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.

Tumor Syndromes: Neurosurgical Evaluation and Management

There are multiple syndromes associated with tumors of the central nervous system (CNS). The most common CNS tumor syndrome is neurofibromatosis-1, with well-defined major and minor criteria needed for diagnosis. Other syndromes with variable degree of CNS and extra-CNS involvement that the neurosurgeon should be aware of include neurofibromatosis-2; Turcot syndrome; Cowden syndrome; Gorlin syndrome; Li-Fraumeni syndrome; ataxia-telangiectasia; multiple endocrine neoplasia type 1; von Hippel-Lindau syndrome; and tuberous sclerosis complex. Although most CNS tumor syndromes follow an autosomal dominant pattern of inheritance, the genetic underpinnings of each disease are complex and increasingly better understood.

[Neuropsychiatric manifestations in Tuberous Sclerosis Complex (TSC): diagnostic guidelines, TAND concept and therapy with mTOR inhibitors]

Neuropsychiatric manifestations in Tuberous Sclerosis Complex (TSC): diagnostic guidelines, TAND concept and therapy with mTOR inhibitors Abstract. Tuberous sclerosis complex (TSC), albeit a rare autosomal-dominant multisystem disease with an incidence of 1:6,000, is one of the most important monogenetic disorders in child and adolescent psychiatry. In up to 90 % of patients, neurological disorders such as epilepsy and psychiatric disorders such as autism spectrum disorder, ADHD, affective disorders, and intellectual disability are observed. In recent years, significant progress has been made in understanding the molecular mechanism as well as in the clinical diagnosis and treatment of the disease. Here, we review these recent developments. In the first part, we describe the need for psychiatric assessment and treatment of patients and analyse challenges in interdisciplinary work between child and adolescent psychiatry, child neurology, and other professional groups. In the second part, we introduce the concept of TSC-associated neuropsychiatric disorders (TAND), developed by the TSC Neuropsychiatry Panel as a guide to help clinical teams, families, and individuals with TSC via screening, assessment, and treatment of neuropsychiatric symptoms and disorders as well as with a novel screening instrument, the TAND Checklist. Finally, we report findings from recent clinical trials of mTOR-inhibitors to treat TAND. The paper includes the German translation of the TAND Checklist as an electronic supplement.

A novel TSC2 missense variant associated with a variable phenotype of tuberous sclerosis complex: case report of a Chinese family

Background

Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disorder characterized by the development of hamartomas in multiple organs, including the brain, heart, skin, kidney, lung and retina. A diagnosis of TSC is established with a recently revised clinical/radiological set of criteria and/or a causative mutation in TSC1 or TSC2 gene.

Case presentation

We report a Chinese TSC family with two siblings presenting with multiple hypomelanotic macules, cardiac rhabdomyomas and cortical tubers associated with a small subependymal nodule. The older child had seizures. A novel heterozygous missense variant in the TSC2 gene (c.899G > T, p.G300 V) was identified and shown to be inherited from their father as well as paternal grandfather, both of whom presented with variable TSC-associated signs and symptoms.

Conclusion

We identified a novel heterozygous TSC2 variant c.899G > T as the causative mutation in a Chinese family with TSC, resulting in wide intrafamilial phenotypic variability. Our study illustrates the importance of clinical evaluation and genetic testing for family members of the patient affected with TSC.

Tuberous sclerosis complex; single center experience

AIM

This study was planned with the aim of retrospectively reviewing the clinical and laboratory findings and therapies of our patients diagnosed with tuberous sclerosis and redefining the patients according to the diagnostic criteria revised by the 2012 International Tuberous Sclerosis Complex Consensus Group and comparing them with the literature.

MATERIALS AND METHOD

Twenty patients diagnosed with tuberous sclerosis complex in the Pediatric Neurology Clinic were examined retrospectively in terms of clinical findings and therapies. The diagnoses were compared again according to 1998 and 2012 criteria.

RESULTS

It was observed that the complaint at presentation was seizure in 17 of 20 patients and hypopigmented spots on the skin in 3 of 20 patients. On the initial physical examination, findings related with the disease were found in the skin in 17 of the patients, in the eye in 5, in the kidneys in 7 and in the brain with imaging in 17. No cardiac involvement was observed in the patients. Infantile spasm was observed in 7 of the patients who presented because of seizure (n=17), partial seizure was observed in 7 and multiple seizure types were observed in 3. It was found that sirolimus treatment was given to 9 of 20 patients because of different reasons, 7 of these 9 patients had epileptic seizures and sirolimus treatment had no effect on epileptic seizures. According to 2012 diagnostic criteria, no marked change occured in the diagnoses of our patients.

CONCLUSIONS

It was observed that the signs and symptoms of our patients were compatible with the literature. Molecular genetic examination was planned for the patients who were being followed up because of probable tuberous sclerosis complex. It was observed that sirolimus treatment had no marked effect on the seizure frequency of our patients.

Pilot validation of the tuberous sclerosis-associated neuropsychiatric disorders (TAND) checklist

BACKGROUND

Tuberous sclerosis complex is a multisystem disorder that includes a range of tuberous sclerosis-associated neuropsychiatric disorders (TAND). The lifetime prevalence rates of TAND are very high; yet surveys suggest that the majority of individuals with tuberous sclerosis never receive appropriate assessment or treatment for TAND. To aid systematic enquiry, a TAND Checklist was developed. Here, we performed pilot validation of the TAND Checklist.

METHOD

Mixed methods were used across two stages. In stage 1, we gathered feedback on the Checklist from tuberous sclerosis "expert professionals" and "expert parents and caregivers." The aim was to examine face and content validity. Stage 2 involved the administration of the refined TAND Checklist to 20 parents of individuals with tuberous sclerosis concurrently with four widely used validated rating scales, to examine external validity and obtain qualitative feedback on face-to-face administration of the TAND Checklist.

RESULTS

Twenty professionals and 62 parents and caregivers from 28 countries participated in the pilot. The TAND Checklist demonstrated good face and content validity with high overall mean and median scores. Qualitative analysis highlighted concerns about the likely use of the TAND Checklist, suggesting that family members and individuals with tuberous sclerosis should drive usage. Stage 2 results showed moderate-to-very good external validity across TAND domain and key subdomains. Internal consistency of domains and subdomains was acceptable to very good. Ninety-three percent of all participants (93%) reported four or more lifetime TAND behavioral difficulties.

CONCLUSION

The pilot validation suggested that the TAND Checklist could provide a useful screening tool in clinical settings.

Impaired social interactions and motor learning skills in tuberous sclerosis complex model mice expressing a dominant/negative form of tuberin

Tuberous sclerosis complex (TSC) is a genetic disorder characterized by the development of hamartomas in multiple organs. Neurological manifestation includes cortical dysplasia, epilepsy, and cognitive deficits such as mental impairment and autism. We measured the impact of TSC2-GAP mutations on cognitive processes and behavior in, ΔRG transgenic mice that express a dominant/negative TSC2 that binds to TSC1, but has mutations affecting its GAP domain and its rabaptin-5 binding motif, resulting in inactivation of the TSC1/2 complex. We performed a behavioral characterization of the ΔRG transgenic mice and found that they display mild, but significant impairments in social behavior and rotarod motor learning. These findings suggest that the ΔRG transgenic mice recapitulate some behavioral abnormalities observed in human TSC patients.

Novel autism subtype-dependent genetic variants are revealed by quantitative trait and subphenotype association analyses of published GWAS data

The heterogeneity of symptoms associated with autism spectrum disorders (ASDs) has presented a significant challenge to genetic analyses. Even when associations with genetic variants have been identified, it has been difficult to associate them with a specific trait or characteristic of autism. Here, we report that quantitative trait analyses of ASD symptoms combined with case-control association analyses using distinct ASD subphenotypes identified on the basis of symptomatic profiles result in the identification of highly significant associations with 18 novel single nucleotide polymorphisms (SNPs). The symptom categories included deficits in language usage, non-verbal communication, social development, and play skills, as well as insistence on sameness or ritualistic behaviors. Ten of the trait-associated SNPs, or quantitative trait loci (QTL), were associated with more than one subtype, providing partial replication of the identified QTL. Notably, none of the novel SNPs is located within an exonic region, suggesting that these hereditary components of ASDs are more likely related to gene regulatory processes (or gene expression) than to structural or functional changes in gene products. Seven of the QTL reside within intergenic chromosomal regions associated with rare copy number variants that have been previously reported in autistic samples. Pathway analyses of the genes associated with the QTL identified in this study implicate neurological functions and disorders associated with autism pathophysiology. This study underscores the advantage of incorporating both quantitative traits as well as subphenotypes into large-scale genome-wide analyses of complex disorders.

Targeted treatments for cognitive and neurodevelopmental disorders in tuberous sclerosis complex

Until recently, the neuropsychiatric phenotype of tuberous sclerosis complex (TSC) was presumed to be caused by the structural brain abnormalities and/or seizures seen in the disorder. However, advances in the molecular biology of the disorder have shown that TSC is a mammalian target of rapamycin (mTOR) overactivation syndrome, and that direct molecular pathways exist between gene mutation and cognitive/neurodevelopmental phenotype. Molecularly-targeted treatments using mTOR inhibitors (such as rapamycin) are showing great promise for the physical and neurological phenotype of TSC. Pre-clinical and early-phase clinical studies of the cognitive and neurodevelopmental features of TSC suggest that some of the neuropsychiatric phenotypes might also be reversible, even in adults with the disorder. TSC, fragile X, neurofibromatosis type 1, and disorders associated with phosphatase and tensin homo (PTEN) mutations, all signal through the mTOR signaling pathway, with the TSC1-TSC2 protein complex as a molecular switchboard at its center. Together, these disorders represent as much as 14% of autism spectrum disorders (ASD). Therefore, we suggest that this signaling pathway is a key to the underlying pathophysiology of a significant subset of individuals with ASD. The study of molecularly targeted treatments in TSC and related disorders, therefore, may be of scientific and clinical value not only to those with TSC, but to a larger population that may have a neuropsychiatric phenotype attributable to mTOR overactivation or dysregulation.

Epilepsy surgery and tuberous sclerosis complex: special considerations

Epilepsy surgery for medically refractory seizures among patients with tuberous sclerosis complex (TSC) is a well-accepted treatment option. Many epilepsy centers around the world have published their experience over the past several years, supporting the idea that the best seizure control is obtained when a single tuber and associated epileptogenic zone is documented and targeted surgically. Recent advances in imaging and physiological techniques that reveal the epileptogenic zone have been used successfully in children with TSC who are being evaluated for surgery. As a result, a number of different surgical strategies have emerged, each reflecting the experience, strengths, and referral biases of the individual treating teams. Experience suggests that some patients with TSC who present with seizures that are difficult to localize and do not meet the classic selection criteria for epilepsy surgery may, nevertheless, benefit from surgery. Tuberectomy alone is often not sufficient for obtaining seizure control. Intracranial electrode recordings performed in a large number of children with TSC undergoing epilepsy surgery have raised new questions about the relationship of the cortical tuber to the epileptogenic zone in TSC. A careful assessment of the risks and benefits of any surgical strategy, compared with those associated with continued refractory epilepsy, should be considered by the treating team in conjunction with the patient's family. Epilepsy surgery has not only benefited many children with TSC, but it also facilitates the understanding of epileptogenesis in TSC.

The psychopathologies of children and adolescents with tuberous sclerosis complex (TSC): a postal survey of UK families

Tuberous Sclerosis Complex (TSC) is a multi-system genetic disorder associated with a wide range of physical features and very high rates of numerous neurocognitive manifestations. However, there is great variability of expression of these features and understanding of the mechanisms underlying this variability is still limited. Mental retardation (MR) and male gender are known to be associated with increased risks of psychopathologies in the general population, but no study has examined these subgroups in TSC as possible contributors to the variable expression observed. It has also remained unclear whether familial-sporadic differences may contribute to variable expression. In this postal survey, UK families reported the frequency and range of physical and behavioural abnormalities in 265 children and adolescents with TSC. Analysis revealed no gender or familial-sporadic differences. Children with MR were significantly more likely to have an autism spectrum disorder, attention deficit-related symptoms and speech and language difficulties. They were more likely to have a history of epilepsy, facial angiofibromata and shagreen patches and tended to have a greater number of physical features of the disorder. However, about one third of the children without MR had features suggestive of a developmental disorder. Anxiety symptoms, depressed mood and aggressive outbursts occurred at equally high rates in those with and without MR. These findings show that TSC can place any child or adolescent at significantly increased risk of a range of neurodevelopmental disabilities. These difficulties, often not recognised, require significant clinical and research attention.

Psychopathology in tuberous sclerosis: an overview and findings in a population-based sample of adults with tuberous sclerosis

BACKGROUND

Tuberous sclerosis (TS) is a multi- system disorder with complex genetics. The neurodevelopmental manifestations of TS are responsible for considerable morbidity. The prevalence of epilepsy and intellectual disabilities among individuals with TS have been well described. Ours is the first study that explores the prevalence and pattern of psychopathology in a population-based sample of adults with TS.

METHODS

Sixty subjects were identified through a capture-recapture analysis of TS. Information was gathered as to seizure history, cognitive functioning (WISC-III) and psychopathology (SADS-L, SAPPA). Lifetime psychopathology was categorized according to Research Diagnostic Criteria. The overall pattern of mental illness (MI) was examined as well as how this varied with IQ and seizure history.

RESULTS

Twenty-four (40.0%) subjects had a history of MI. The most common diagnosis was that of an affective disorder [18 (30.0%)], the majority of which were major depressive episodes. Alcoholism [4 (6.7%)] and anxiety disorders [3 (5.0%)] were the next most common diagnoses. Two (3.3%) subjects had had a tic disorder. Only one individual had a diagnosis of schizophrenia. MI was found in 75.0% of those with a history of epilepsy and 37.5% of those without epilepsy. MI was significantly more prevalent in those with a full-scale IQ above 70.

CONCLUSIONS

A significant proportion of adult with TS experience MI. MI was significantly more [corrected] prevalent in subjects with a full-scale IQ above 70. Reasons for such a finding are explored, and related methodological considerations for future research outlined.

Consensus clinical guidelines for the assessment of cognitive and behavioural problems in Tuberous Sclerosis

Tuberous Sclerosis (TSC) is a genetic disorder characterised by abnormal growths in a wide range of organs. In the brain, abnormalities of differentiation, proliferation and migration can produce a range of neuropsychiatric features such as mental retardation, autism and ADHD. Although these manifestations are not diagnostic of the disorder, cognitive and behavioural features are often of greatest concern to families yet limited clinical assessment and interventions are currently offered. A consensus panel at a TSC Brain/Behaviour workshop recommended that the cognitive and behavioural profiles of individuals with TSC should be assessed at regular intervals in a planned fashion in accordance with the difficulties associated with the disorder. Evaluations should include the use of standardised neuropsychological and behavioural tools as appropriate to the age and developmental level of the individual assessed. These cognitive and behavioural profiles should be incorporated in the overall formulation of the needs of the person with TSC to plan educational, social and clinical management strategies. Assessments should be documented so that individual longitudinal progress can be monitored. The paper outlines the problems associated with TSC, the purpose of recommended assessments, developmentally appropriate stages for assessment, and identifies specific areas that should be targeted for assessment.

Specific Genetic Disorders and Autism: Clinical Contribution Towards their Identification

Autism is a heterogeneous disorder that can reveal a specific genetic disease. This paper describes several genetic diseases consistently associated with autism (fragile X, tuberous sclerosis, Angelman syndrome, duplication of 15q11-q13, Down syndrome, San Filippo syndrome, MECP2 related disorders, phenylketonuria, Smith-Magenis syndrome, 22q13 deletion, adenylosuccinate lyase deficiency, Cohen syndrome, and Smith-Lemli-Opitz syndrome) and proposes a consensual and economic diagnostic strategy to help practitioners to identify them. A rigorous initial clinical screening is presented to avoid unnecessary laboratory and imaging studies. Regarding psychiatric nosography, the concept of "syndromal autism"--autism associated with other clinical signs should be promoted because it may help to distinguish patients who warrant a multidisciplinary approach and further investigation.

Behavioral and cognitive aspects of tuberous sclerosis complex

Tuberous sclerosis complex is a multisystem genetic disorder. Of all the possible manifestations of this complex disorder, the cognitive and behavioral problems represent the area of greatest concern to parents and caregivers. This review outlines the current evidence regarding global intellectual abilities, behavioral problems, psychiatric diagnoses, learning disorders, and specific neuropsychologic deficits for which individuals with tuberous sclerosis complex are at particularly increased risk, and outlines approaches to intervention. Approximately half of individuals diagnosed with tuberous sclerosis complex present with global intellectual impairment and developmental psychopathologies. Those with normal intellectual abilities are also at high risk of specific neuropsychologic deficits and behavioral, learning, and other psychiatric disorders. There is no evidence for an inevitable decline in cognition or behavior, and any such changes should be investigated. The evolving neurocognitive literature suggests that frontal brain systems might be most consistently disrupted by tuberous sclerosis complex-related neuropathology, thus leading to abnormalities in regulatory and goal-directed behaviors.

A patient with TSC1 germline mutation whose clinical phenotype was limited to lymphangioleiomyomatosis

BACKGROUND

Lymphangioleiomyomatosis (LAM) can occur as in isolated form (sporadic LAM) or as a pulmonary manifestation of tuberous sclerosis complex (TSC) (TSC-associated LAM). Recent studies, however, revealed that both forms of LAM are genetically related but that sporadic LAM is a distinct clinical entity caused by somatic mutations of TSC2 (not TSC1) rather than a forme fruste of TSC carrying either of the TSC1 or TSC2 germline mutations.

METHOD

Case presentation and in-depth molecular and histopathological examinations. A 34-year-old Japanese woman was diagnosed as having pulmonary lymphangioleiomyomatosis (LAM) when bilateral pneumothoraces were surgically treated in 1992. Although slowly progressive renal disfunction was observed due to bilateral multiple renal cysts during the past 4 years, she had no other clinical features of TSC and was diagnosed as having sporadic LAM with multiple renal cysts of undetermined aetiology. Her subsequent clinical course was complicated by an endobrochial carcinoid tumour, which eventually resulted in her death in June 1999 due to massive haemoptysis.

RESULTS

Postmortem examination revealed the presence of LAM lesions in the lungs, mediastinal lymph nodes, kidneys and uterus. Diffuse renal LAM lesions are presumed to generate multiple renal cysts by constricting the nephron rather than epithelial hyperplasia obstructing lumina, which is analysis of the TSC genes demonstrated that she did not have TSC2/PKD1 contiguous gene syndrome but had a TSC1 germline mutation (Sato T et al. J Hum Genet 2002; 47: 20-8) that had occured de novo.

CONCLUSION

This patient therefore illustrates that clinical manifestations of TSC are sufficiently diverse as to allow a forme fruste of TSC that mimics sporadic LAM and that TSC1 mutation can cause multiple renal cysts resulting in renal failure.

Neuropsychiatric problems in tuberous sclerosis complex

Tuberous sclerosis complex is an autosomal dominant disorder characterized by abnormal cellular differentiation and proliferation, as well as abnormal neuronal migration. It is a disease affecting multiple organ systems and typically has brain involvement, causing severe disabilities. This article reviews the literature of the commonly associated neuropsychiatric complications, including mental retardation, autism-like features, and other behavior problems, which are discussed in the context of the neuropathology and epilepsy observed in tuberous sclerosis complex. The potential pathogenesis of neuropsychiatric problems is explored, including links to the genetics, neuropathology, neurotrophins, and epilepsy factors associated with tuberous sclerosis complex. Treatment of neuropsychiatric symptoms, including autism-like features, attention deficits, and sleep disorders, is also discussed.

Association between a high-expressing interferon-gamma allele and a lower frequency of kidney angiomyolipomas in TSC2 patients

Tuberous sclerosis complex (TSC) is a familial hamartoma syndrome in which renal involvement is common and, at times, life threatening. We have investigated the potential effect of a non-TSC gene on renal disease in a cohort of 172 TSC patients with TSC2 mutations. Patients were genotyped for an interferon-gamma (IFN-gamma) microsatellite polymorphism, within intron 1, for which one common allele (allele 2, with 12 CA repeats) has been shown to have a higher expression of IFN-gamma. A chi(2) analysis was used to examine the association between IFN-gamma allele 2 and the development of kidney angiomyolipomas (KAMLs) in this TSC2 cohort. Because of the age-dependent development of KAMLs in TSC, we initially focused on the 127 patients who were >5 years old. Additional subgroup analyses were done to investigate the influence of age and gender. The transmission/disequilibrium test (TDT) was also performed in a subset of this cohort (46 probands) for whom parent and/or sibling samples were available for analysis. Both chi(2) analysis and TDT suggested an association between IFN-gamma allele 2 and the absence of KAMLs in patients who have known TSC2 mutations. Among the 127 patients who were >5 years old, KAMLs were present in 95 (75%) and were absent in 32 (25%). In the group with KAML present, the frequency of IFN-gamma allele 2 was 56%; in the group with KAML absent, the frequency of IFN-gamma allele 2 was significantly higher, at 78% (P=.02, by chi(2) analysis). The family-based TDT analysis gave similar results, with a TDT statistic (TDT chi2=5.45) corresponding to a P value of.02. Subgroup analyses show that both age and gender may influence the impact of this association. Although these results should be replicated in other populations with TSC, the present study suggests that modifier genes play a role in the variable expression of TSC and also suggests a potential therapy for KAMLs in patients with TSC.

Neuropathology of tuberous sclerosis

In the cerebrum of patients with tuberous sclerosis (TSC), there are three types of nodular lesions: cortical tubers, subcortical heterotopic nodules and subependymal giant cell astrocytomas. Histologically, these hamartias and hamartomas contain abnormal giant cells that show evidence of abnormal differentiation of immature neural cells. Recent identification of the TSC1 and TSC2 genes has facilitated studies of the molecular pathology of TSC. The expression of their protein products, hamartin and tuberin, is altered in various TSC lesions. However, the molecular mechanism by which cortical tubers develop remains to be elucidated. The Eker rat, a naturally occurring animal model of TSC, will provide a powerful tool for future investigations of TSC.

Deletions spanning the neurofibromatosis type 1 gene: implications for genotype-phenotype correlations in neurofibromatosis type 1?

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder characterized by abnormalities of tissues predominantly derived from the neural crest. Symptoms are highly variable and severity cannot be predicted, even within families. DNA of 84 unrelated patients with NF1, unselected for clinical features or severity, were screened with intragenic polymorphic repeat markers and by Southern analysis with cDNA probes. Deletions of the entire gene were detected in five patients from four unrelated families. Their phenotype resembled that of five previously reported patients with deletions, including intellectual impairment and dysmorphic features, but without an excessive number of dermal neurofibromas. This report supports the hypothesis that large deletions spanning the entire NF1 gene may lead to a specific phenotype.

Tuberöse Sklerose und organische bipolare Störung bei einer 15jährigen Jugendlichen

Zusammenfassung: Wir berichten über eine Patientin mit tuberöser Sklerose, die im Alter von 15 Jahren unter antiepileptischer Medikation mit Oxcarbazepin mehrere rasch wechselnde Episoden (rapid cycling) einer bipolaren Erkrankung entwickelte. Eine Kombinationsbehandlung mit Oxcarbazepin und Valproat bei in dieser Phase erstmals auftretenden Grand-mal-Anfällen erwies sich als nicht ausreichend zur Prophylaxe der affektiven Symptomatik. Eine wesentliche Stabilisierung des klinischen Bildes erfolgte unter zusätzlicher, niedrig dosierter Lithium-Einstellung, die durch wiederholt auftretende Hyperkaliämien erschwert wurde.

Autism and tuberous sclerosis

Autism and pervasive developmental disorders (PDD) are common in tuberous sclerosis (TSC). The frequency of autism is about 25%, with 40-45% of TSC cases meeting criteria for autism or PDD. Among autistic populations, the frequency of TSC is 1-4% and perhaps as high as 8-14% among the subgroup of autistic individuals with a seizure disorder. Mental retardation (MR) and seizures, particularly infantile spasms, are significant risk factors in the development of autism/PDD in TSC; however, neither are sufficient or necessary for the development of these behaviors. The mechanism underlying the association of autism and TSC is as yet unclear but clinical features and neuroimaging investigations suggest that an abnormal TSC gene may directly influence the development of autism rather than it being a secondary effect of seizures or MR. The presence of autism/PDD may arise if the TSC gene mutations occur at critical stages of neural development in neural tissue of brain regions critical in the development of autism.

The genetic basis of tuberous sclerosis

Tuberous sclerosis is a relatively common inherited disease that causes multiple benign tumours in different organs, frequently leading to skin rashes, seizures and mental handicap. The disease can be caused by mutations in either of two genes, TSC2, identified in 1993, and TSC1, only recently identified. Here we review the current state of knowledge of the molecular genetics of tuberous sclerosis and the spectrum of mutations seen in and the implications of recent findings for patients. Although both genes appear to function as tumour suppressors, the function of their protein products is not understood. A speculative model of how these proteins might function is briefly described.

Autism in tuberous sclerosis complex

The frequency and clinical presentation of autism in 28 probands with tuberous sclerosis complex (TSC) are reported and risk factors that may influence the development of autism in TSC are examined. Eight probands meet ICD-10 and DSM-IV criteria for autism, an additional 4 meet criteria for pervasive developmental disorder (PDD). Twelve TSC probands with autism/PDD are compared to 16 TSC probands without these conditions for factors which may underlie the association of autism and TSC. A specific seizure type, infantile spasms, as well as mental retardation, are increased in the TSC, autistic/PDD group. Furthermore, rates of social phobia and substance abuse are elevated among first-degree relatives of TSC probands with autism compared to first-degree relatives of TSC probands without autism. Implications of these findings in understanding the association of autism and TSC are discussed.

The GAP-related domain of tuberin, the product of the TSC2 gene, is a target for missense mutations in tuberous sclerosis

Tuberous sclerosis is an autosomal dominant trait in which the dysregulation of cellular proliferation and differentiation results in the development of hamartomatous growths in many organs. The TSC2 gene is one of two genes determining tuberous sclerosis. Inactivating germline mutations of TSC2 in patients with tuberous sclerosis and somatic loss of heterozygosity at the TSC2 locus in the associated hamartomas indicate that TSC2 functions as a tumour suppressor gene and that loss of function is critical to expression of the tuberous sclerosis phenotype. The TSC2 product, tuberin, has a region of homology with the GTPase activating protein rap1GAP and stimulates the GTPase activity of rap1a and rab5a in vitro. Here we show that the region of homology between tuberin and human rap1GAP and the murine GAP mSpa1 is more extensive than previously reported and spans approximately 160 amino acid residues encoded within exons 34-38 of the TSC2 gene. Single strand conformation polymorphism analysis of these exons in 173 unrelated patients with tuberous sclerosis and direct sequencing of variant conformers together with study of additional family members enabled characterisation of disease associated mutations in 14 cases. Missense mutations, which occurred in exons 36, 37 and 38 were identified in eight cases, four of whom shared the same recurrent change P1675L. Each of the five different missense mutations identified was shown to occur de novo in at least one sporadic case of tuberous sclerosis. The high proportion of missense mutations detected in the region of the TSC2 gene encoding the GAP-related domain supports its key role in the regulation of cellular growth.

Identification of a nonsense mutation at the 5' end of the TSC2 gene in a family with a presumptive diagnosis of tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal dominantly inherited disease with a high mutation rate. It is clinically a very variable disorder and hamartomas can occur in many different organs. TSC shows genetic heterogeneity; one gene, TSC1, is on chromosome 9q34, and the second gene, TSC2, on chromosome 16p13.3. Clinical criteria for diagnosis have been established, but diagnosis of patients with minimal expression of the disease can be very difficult. In children the phenotype is often incomplete or not fully assessable. Hence mildly affected subjects, at risk for severely affected offspring, may remain undiagnosed. The detection of (small) mutations in the tuberous sclerosis gene located on chromosome 16 (TSC2) has recently become possible and may be helpful in the diagnosis of ambiguous cases. To our knowledge, this is the first report of a point mutation in the TSC2 gene in a familial case of tuberous sclerosis. A nonsense mutation was detected in a family in which the father had only minor signs hinting at tuberous sclerosis. The son had multiple cardiac tumours and white patches, but full clinical investigation was impossible in this child. This case illustrates that mutation analysis can contribute to a diagnosis of tuberous sclerosis in families with an incomplete phenotype.

Autism: towards an integration of clinical, genetic, neuropsychological, and neurobiological perspectives

Autism constitutes one of the best validated child psychiatric disorders. Empirical research has succeeded in delineating the key clinical phenomena, in demonstrating strong genetic influences on the underlying liability, and in identifying basic cognitive deficits. A range of neurobiological abnormalities has also been found, although the replicability of specific findings has not been high. An understanding of the causal processes leading to autism, and accounting for the marked variability in its manifestations, requires an integration across these different levels of enquiry. Although this is not yet possible, a partial integration provides a useful strategy for identifying key research questions, the limitations of existing hypotheses, and future research directions that are likely to prove fruitful. The research findings for each research level are critically reviewed in order to consider how to move towards an integration across levels.