Autism spectrum disorders in tuberous sclerosis: pathogenetic pathways and implications for treatment

Microtubule Cytoskeletal Network Alterations in a Transgenic Model of Tuberous Sclerosis Complex: Relevance to Autism Spectrum Disorders

Tuberous sclerosis complex (TSC) is a rare genetic multisystem disorder caused by loss-of-function mutations in the tumour suppressors TSC1/TSC2, both of which are negative regulators of the mammalian target of rapamycin (mTOR) kinase. Importantly, mTOR hyperactivity seems to be linked with the pathobiology of autism spectrum disorders (ASD). Recent studies suggest the potential involvement of microtubule (MT) network dysfunction in the neuropathology of "mTORopathies", including ASD. Cytoskeletal reorganization could be responsible for neuroplasticity disturbances in ASD individuals. Thus, the aim of this work was to study the effect of Tsc2 haploinsufficiency on the cytoskeletal pathology and disturbances in the proteostasis of the key cytoskeletal proteins in the brain of a TSC mouse model of ASD. Western-blot analysis indicated significant brain-structure-dependent abnormalities in the microtubule-associated protein Tau (MAP-Tau), and reduced MAP1B and neurofilament light (NF-L) protein level in 2-month-old male B6;129S4-Tsc2^tm1Djk/J mice. Alongside, pathological irregularities in the ultrastructure of both MT and neurofilament (NFL) networks as well as swelling of the nerve endings were demonstrated. These changes in the level of key cytoskeletal proteins in the brain of the autistic-like TSC mice suggest the possible molecular mechanisms responsible for neuroplasticity alterations in the ASD brain.

Ketogenic Diet Therapy for Drug-Resistant Epilepsy and Cognitive Impairment in Children With Tuberous Sclerosis Complex

OBJECTIVE

Tuberous sclerosis complex (TSC) is a rare disease with a high risk of epilepsy and cognitive impairment in children. Ketogenic diet (KD) therapy has been consistently reported to be beneficial to TSC patients. In this study, we aimed to investigate the efficacy and safety of KD in the treatment of drug-resistant epilepsy and cognitive impairment in children with TSC.

METHODS

In this multicenter study, 53 children (33 males and 20 females) with drug-resistant epilepsy or cognitive impairment caused by TSC were retrospectively recruited from 10 hospitals from January 1, 2010, to December 31, 2020. Intention-to-treat analysis was used to evaluate seizure reduction and cognition improvement as outcomes after KD therapy.

RESULTS

Of the 53 TSC patients included, 51 failed to be seizure-free with an average of 5.0 (range, 4-6) different anti-seizure medications (ASMs), before KD therapy. Although the other two patients achieved seizure freedom before KD, they still showed psychomotor development delay and electroencephalogram (EEG) abnormalities. At 1, 3, 6, and 12 months after the KD therapy, 51 (100%), 46 (90.2%), 35 (68.6%), and 16 patients (31.4%) remained on the diet therapy, respectively. At these time points, there were 26 (51.0%), 24 (47.1%), 22 (43.1%) and 13 patients (25.5%) having ≥50% reductions in seizure, including 11 (21.6%), 12 (23.5%), 9 (17.6%) and 3 patients (5.9%) achieving seizure freedom. In addition, of 51 patients with psychomotor retardation, 36 (36 of 51, 70.6%) showed cognitive and behavioral improvements. During the KD therapy, no serious side effects occurred in any patient. The most common side effects were gastrointestinal disturbance (20 of 53, 37.7%) and hyperlipidemia (6 of 53, 11.3%). The side effects were gradually relieved after adjustment of the ketogenic ratio and symptomatic treatment.

CONCLUSION

KD is an effective and safe treatment for TSC-related drug-resistant epilepsy and cognitive impairment in children. KD can reduce seizure frequency and may potentially improve cognition and behavior.

Profile of Autism Spectrum Disorder in Tuberous Sclerosis Complex: Results from a Longitudinal, Prospective, Multisite Study

OBJECTIVE

Tuberous sclerosis complex (TSC) is highly associated with autism spectrum disorder (ASD). Objectives of the study were to characterize autistic features in young children with TSC.

METHODS

Participants included 138 children followed from ages 3 to 36 months with TSC from the Tuberous Sclerosis Complex Autism Center of Excellence Research Network (TACERN), a multicenter, prospective observational study aimed at understanding the underlying mechanisms of ASD in TSC. Developmental and autism-specific assessments were administered, and a clinical diagnosis of ASD was determined for all participants at 36 months. Further analyses were performed on 117 participants with valid autism assessments based on nonverbal mental age greater than 15 months.

RESULTS

Prevalence of clinical diagnosis of ASD at 36 months was 25%. Nearly all autistic behaviors on the Autism Diagnostic Observation Schedule-2 (ADOS-2) and Autism Diagnostic Interview-Revised (ADI-R) were more prevalent in children diagnosed with ASD; however, autism-specific behaviors were also observed in children without ASD. Overall quality of social overtures, facial expressions, and abnormal repetitive interests and behaviors were characteristics most likely to distinguish children with ASD from those without an ASD diagnosis. Participants meeting ADOS-2 criteria but not a clinical ASD diagnosis exhibited intermediate developmental and ADOS-2 scores compared to individuals with and without ASD.

INTERPRETATION

ASD is highly prevalent in TSC, and many additional individuals with TSC exhibit a broad range of subthreshold autistic behaviors. Our findings reveal a broader autism phenotype that can be identified in young children with TSC, which provides opportunity for early targeted treatments. ANN NEUROL 2021.

Review of the treatment options for epilepsy in tuberous sclerosis complex: towards precision medicine

Tuberous sclerosis complex (TSC) is a rare genetic disorder caused by mutations in the TSC1 or TSC2 genes, which encode proteins that antagonise the mammalian isoform of the target of rapamycin complex 1 (mTORC1) - a key mediator of cell growth and metabolism. TSC is characterised by the development of benign tumours in multiple organs, together with neurological manifestations including epilepsy and TSC-associated neuropsychiatric disorders (TAND). Epilepsy occurs frequently and is associated with significant morbidity and mortality; however, the management is challenging due to the intractable nature of the seizures. Preventative epilepsy treatment is a key aim, especially as patients with epilepsy may be at a higher risk of developing severe cognitive and behavioural impairment. Vigabatrin given preventatively reduces the risk and severity of epilepsy although the benefits for TAND are inconclusive. These promising results could pave the way for evaluating other treatments in a preventative capacity, especially those that may address the underlying pathophysiology of TSC, including everolimus, cannabidiol and the ketogenic diet (KD). Everolimus is an mTOR inhibitor approved for the adjunctive treatment of refractory TSC-associated seizures that has demonstrated significant reductions in seizure frequency compared with placebo, improvements that were sustained after 2 years of treatment. Highly purified cannabidiol, recently approved in the US as Epidiolex® for TSC-associated seizures in patients ⩾1 years of age, and the KD, may also participate in the regulation of the mTOR pathway. This review focusses on the pivotal clinical evidence surrounding these potential targeted therapies that may form the foundation of precision medicine for TSC-associated epilepsy, as well as other current treatments including anti-seizure drugs, vagus nerve stimulation and surgery. New future therapies are also discussed, together with the potential for preventative treatment with targeted therapies. Due to advances in understanding the molecular genetics and pathophysiology, TSC represents a prototypic clinical syndrome for studying epileptogenesis and the impact of precision medicine.

[Genetic risk factors and their influence on neural development in autism spectrum disorders]

Genetic risk factors and their influence on neural development in autism spectrum disorders Abstract. Abstract. Autism spectrum disorders are etiologically based on genetic and specific gene x biologically relevant environmental risk factors. They are diagnosed based on behavioral characteristics, such as impaired social communication and stereotyped, repetitive behavior and sensory as well as special interests. The genetic background is heterogeneous, i. e., it comprises diverse genetic risk factors across the disorder and high interindividual differences of specific genetic risk factors. Nevertheless, risk factors converge regarding underlying biological mechanisms and shared pathways, which likely cause the autism-specific behavioral characteristics. The current selective literature review summarizes differential genetic risk factors and focuses particularly on mechanisms and pathways currently being discussed by international research. In conclusion, clinically relevant aspects and open translational research questions are presented.

Beyond Baby Siblings-Expanding the Definition of "High-Risk Infants" in Autism Research

PURPOSE OF REVIEW

Much of our understanding of early development in children with autism spectrum disorder (ASD) comes from studies of children with a family history of autism. We reviewed the current literature on neurodevelopmental profiles and autism prevalence from other high-risk infant groups to expose gaps and inform next steps. We focused on infants with early medical risk (e.g., preterm birth) and genetic risk (tuberous sclerosis complex [TSC]).

RECENT FINDINGS

About 7% of very preterm infants are later diagnosed with ASD. Prospective studies of early development outside of familial-risk infants are rare; however, recent work within preterm and TSC infants suggests interesting similarities and differences from infants with a family history of ASD. It is essential that we extend our knowledge of early markers of ASD beyond familial-risk infants to expand our knowledge of autism as it emerges in order to develop better, more individualized early interventions.

Factors Affecting Family Compliance with Genetic Testing of Children Diagnosed with Autism Spectrum Disorder

There is broad consensus about the importance of post-diagnostic genetic testing for children with ASD. However, the extent of compliance with these tests and the factors affecting compliance have rarely been examined. We surveyed a sample of 114 families with a child with ASD in Israel, where such genetic testing is funded by the government. We found that only one-third of these families completed post-diagnosis genetic testing for their child. The main factor influencing compliance was the doctor's recommendation (OR 11.6; 95% CI 3.2-42.4; p < 0.001). Furthermore, > 50% of the non-compliant families reported that genetic testing was irrelevant to them. Our findings highlight the importance of providing clear recommendations and explanations regarding the benefits and relevance of post-diagnosis genetic testing for children with ASD.

Epilepsy and Neurodevelopmental Comorbidities in Tuberous Sclerosis Complex: A Natural History Study

BACKGROUND

We studied the natural history, genotype influence, and inter-relationship of epilepsy and neuropsychiatric disorders in tuberous sclerosis complex.

METHODS

Patients were identified using the TSC Natural History Database, the largest repository of longitudinally studied patients enrolled by the TSC Clinics Consortium.

RESULTS

A cohort of 1657 TSC Natural History Database patients was analyzed. Eighty-eight percent patients (91% TSC2 vs 82% TSC1; P = 0.002) had epilepsy; TSC2 was more frequent with epilepsy onset at age less than two years (TSC2 82% vs TSC1 54%; P < 0.001) and infantile spasms (TSC2 56% vs TSC1 27%; P < 0.001). Frequency of intellectual disability (intelligence quotient less than 70) was higher when epilepsy coexisted (P < 0.001), but was not impacted by genotype (P = 0.08). Severe intellectual disability (intelligence quotient less than 50) was associated with epilepsy onset at age less than two years (P = 0.007), but not with the epilepsy duration (P = 0.45). Autism was diagnosed in 23% and was associated with epilepsy (P < 0.001), particularly with epilepsy onset at age less than two years (P = 0.02) but not with genotype (P = 0.06). Attention-deficit/hyperactivity disorder (age greater than four years) was diagnosed in 18% and was associated with epilepsy (P < 0.001), but genotype made no difference. Nine percent had anxiety (age greater than seven years) and 6% had depression (age greater than nine years), but neither showed association with epilepsy or genotype.

CONCLUSIONS

Epilepsy is associated with intellectual disability, and when epilepsy begins before age two years the frequency and severity of intellectual disability is much higher. Epilepsy is also associated with autism and attention-deficit/hyperactivity disorder but not with anxiety and depression. Additional trials, blinded, prospective, and adequately powered, will help clarify if early and effective treatment of epilepsy may also mitigate intellectual disability, autism, and attention-deficit/hyperactivity disorder.

Improving Developmental Abilities in Infants With Tuberous Sclerosis Complex: A Pilot Behavioral Intervention Study

Tuberous sclerosis complex (TSC) is a rare genetic syndrome that confers risk for neurodevelopmental disorders, including autism spectrum disorder and intellectual disability. Delays in social communication and early cognitive abilities are observable as early as 9 months of age in children with TSC; however, there have been no studies of early behavioral intervention in TSC. We conducted a pilot study of an evidence-based, parent-mediated behavioral intervention focused on improving early social communication and play skills in 5 children with TSC (aged 1-3 years). Participants showed maintenance and sometimes gains in developmental abilities, relative to peers, following intervention. Parents generally found the intervention to be helpful and were able to administer the intervention with fidelity. Preliminary results demonstrate initial feasibility of an early play-based, parent-mediated intervention and support the need for a large-scale, randomized clinical trial in TSC.

Chronic activation of anti-oxidant pathways and iron accumulation in epileptogenic malformations

Aims

Oxidative stress is evident in resected epileptogenic brain tissue of patients with developmental brain malformations related to mammalian target of rapamycin activation: tuberous sclerosis complex (TSC) and focal cortical dysplasia type IIb (FCD IIb). Whether chronic activation of anti‐oxidant pathways is beneficial or contributes to pathology is not clear.

Methods

We investigated oxidative stress markers, including haem oxygenase 1, ferritin and the inflammation associated microRNA‐155 in surgically resected epileptogenic brain tissue of TSC (n = 10) and FCD IIb (n = 8) patients and in a TSC model (Tsc1^GFAP−/− mice) using immunohistochemistry, in situ hybridization, real‐time quantitative PCR and immunoblotting. Using human foetal astrocytes we performed an in vitro characterization of the anti‐oxidant response to acute and chronic oxidative stress and evaluated overexpression of the disease‐relevant pro‐inflammatory microRNA‐155.

Results

Resected TSC or FCD IIb tissue displayed higher expression of oxidative stress markers and microRNA‐155. Tsc1^GFAP−/− mice expressed more microRNA‐155 and haem oxygenase 1 in the brain compared to wild‐type, preceding the typical development of spontaneous seizures in these animals. In vitro, chronic microRNA‐155 overexpression induced haem oxygenase 1, iron regulatory elements and increased susceptibility to oxidative stress. Overexpression of iron regulatory genes was also detected in patients with TSC, FCD IIb and Tsc1^GFAP−/− mice.

Conclusion

Our results demonstrate that early and sustained activation of anti‐oxidant signalling and dysregulation of iron metabolism are a pathological hallmark of FCD IIb and TSC. Our findings suggest novel therapeutic strategies aimed at controlling the pathological link between both processes.

Corticostriatal Transmission Is Selectively Enhanced in Striatonigral Neurons with Postnatal Loss of Tsc1

mTORC1 is a central signaling hub that integrates intra- and extracellular signals to regulate a variety of cellular metabolic processes. Mutations in regulators of mTORC1 lead to neurodevelopmental disorders associated with autism, which is characterized by repetitive, inflexible behaviors. These behaviors may result from alterations in striatal circuits that control motor learning and habit formation. However, the consequences of mTORC1 dysregulation on striatal neuron function are largely unknown. To investigate this, we deleted the mTORC1 negative regulator Tsc1 from identified striatonigral and striatopallidal neurons and examined how cell-autonomous upregulation of mTORC1 activity affects their morphology and physiology. We find that loss of Tsc1 increases the excitability of striatonigral, but not striatopallidal, neurons and selectively enhances corticostriatal synaptic transmission. These findings highlight the critical role of mTORC1 in regulating striatal activity in a cell type- and input-specific manner, with implications for striatonigral pathway dysfunction in neuropsychiatric disease.

Resting-State fMRI Networks in Children with Tuberous Sclerosis Complex

BACKGROUND AND PURPOSE

There are no published studies examining resting state networks (RSNs) and their relationship with neurodevelopmental metrics in tuberous sclerosis complex (TSC). We aimed to identify major resting-state functional magnetic resonance imaging (rs-fMRI) networks in infants with TSC and correlate network analyses with neurodevelopmental assessments, autism diagnosis, and seizure history.

METHODS

Rs-fMRI data from 34 infants with TSC, sedated with propofol during the scan, were analyzed to identify auditory, motor, and visual RSNs. We examined the correlations between auditory, motor, and visual RSNs at approximately 11.5 months, neurodevelopmental outcome at approximately 18.5 months, and diagnosis of autism spectrum disorders at approximately 36 months of age.

RESULTS

RSNs were obtained in 76.5% (26/34) of infants. We observed significant negative correlations between auditory RSN and auditory comprehension test scores (p = .038; r = -.435), as well as significant positive correlations between motor RSN and gross motor skills test scores (p = .023; r = .564). Significant positive correlations between motor RSNs and gross motor skills (p = .012; r = .754) were observed in TSC infants without autism, but not in TSC infants with autism, which could suggest altered motor processing. There were no significant differences in RSNs according to seizure history.

CONCLUSIONS

Negative correlation between auditory RSN, as well as positive correlation between motor RSN and developmental outcome measures might reflect different brain mechanisms and, when identified, may be helpful in predicting later function. A larger study of TSC patients with a healthy control group is needed before auditory and motor RSNs could be considered as neurodevelopmental outcome biomarkers.

Early Clinical Predictors of Autism Spectrum Disorder in Infants with Tuberous Sclerosis Complex: Results from the EPISTOP Study

Autism spectrum disorder (ASD) is highly prevalent in subjects with Tuberous Sclerosis Complex (TSC), but we are not still able to reliably predict which infants will develop ASD. This study aimed to identify the early clinical markers of ASD and/or developmental delay (DD) in infants with an early diagnosis of TSC. We prospectively evaluated 82 infants with TSC (6-24 months of age), using a detailed neuropsychological assessment (Bayley Scales of Infant Development-BSID, and Autism Diagnostic Observation Schedule-ADOS), in the context of the EPISTOP (Long-term, prospective study evaluating clinical and molecular biomarkers of EPIleptogenesiS in a genetic model of epilepsy-Tuberous SclerOsis ComPlex) project (NCT02098759). Normal cognitive developmental quotient at 12 months excluded subsequent ASD (negative predictive value 100%). The total score of ADOS at 12 months clearly differentiated children with a future diagnosis of ASD from children without (p = 0.012). Atypical socio-communication behaviors (p < 0.001) were more frequently observed than stereotyped/repetitive behaviors in children with ASD at 24 months. The combined use of BSID and ADOS can reliably identify infants with TSC with a higher risk for ASD at age 6-12 months, allowing for clinicians to target the earliest symptoms of abnormal neurodevelopment with tailored intervention strategies.

A Synaptic Perspective of Fragile X Syndrome and Autism Spectrum Disorders

Altered synaptic structure and function is a major hallmark of fragile X syndrome (FXS), autism spectrum disorders (ASDs), and other intellectual disabilities (IDs), which are therefore classified as synaptopathies. FXS and ASDs, while clinically and genetically distinct, share significant comorbidity, suggesting that there may be a common molecular and/or cellular basis, presumably at the synapse. In this article, we review brain architecture and synaptic pathways that are dysregulated in FXS and ASDs, including spine architecture, signaling in synaptic plasticity, local protein synthesis, (m)RNA modifications, and degradation. mRNA repression is a powerful mechanism for the regulation of synaptic structure and efficacy. We infer that there is no single pathway that explains most of the etiology and discuss new findings and the implications for future work directed at improving our understanding of the pathogenesis of FXS and related ASDs and the design of therapeutic strategies to ameliorate these disorders.

Disruption of mTOR and MAPK pathways correlates with severity in idiopathic autism

The molecular signature underlying autism spectrum disorder remains largely unknown. This study identifies differential expression of mTOR and MAPK pathways in patients affected by mild and severe idiopathic autism. A total of 55 subjects were enrolled, of which 22 were typically developing individuals and 33 were patients aged between 3 and 11 years, with autism spectrum disorder. A detailed history, including physical examination, developmental evaluation, mental health history and autism diagnostic observation schedule were performed for each patient. Components of the mTOR and MAPK signalling pathways were analysed from peripheral blood at the protein level. Patients were then stratified according to their clinical phenotypes, and the molecular profiling was analysed in relation to the degree of autism severity. In this cohort of patients, we identified increased activity of mTOR and the MAPK pathways, key regulators of synaptogenesis and protein synthesis. Specifically, rpS6, p-eIF4E, TSC1 and p-MNK1 expression discriminated patients according to their clinical diagnosis, suggesting that components of protein synthesis signalling pathways might constitute a molecular signature of clinical severity in autism spectrum disorder.

Everolimus for epilepsy and autism spectrum disorder in tuberous sclerosis complex: EXIST-3 substudy in Japan

BACKGROUND

Epilepsy and autism spectrum disorder (ASD) are the common neurological manifestations of tuberous sclerosis complex (TSC). EXIST-3 study has recently demonstrated that everolimus reduces seizures in patients with TSC and refractory epilepsy. Here we report the efficacy and safety of everolimus for treatment-refractory seizures in Japanese patients of EXIST-3, along with the exploratory analysis evaluating the everolimus effect on comorbid ASD symptoms in these patients.

METHODS

Primary endpoint was change in seizure frequency from baseline defined as response rate (≥50% reduction) and median percentage reduction in the seizure frequency. Pervasive Developmental Disorders Autism Society Japan Rating Scale (PARS) scores were assessed at baseline and at week-18 for ASD symptoms.

RESULTS

Overall, 35 Japanese patients were randomized to everolimus low-exposure (LE; n = 10), everolimus high-exposure (HE; n = 14), or placebo (n = 11). The response rate was 30.0% and 28.6% versus 0% with the everolimus LE and HE versus placebo arm, respectively. Similarly, the median percentage reduction in seizure frequency was 6.88% and 38.06% versus -6.67%. Stomatitis was the most frequently reported adverse event (everolimus LE, 100%; HE, 78.6%; placebo, 9.1%). Four of 11 patients with ASD in the everolimus arms and 1 of 8 patients with ASD in the placebo arm showed ≥5 point decrease in PARS scores.

CONCLUSIONS

Adjunctive everolimus treatment improved seizure frequency with a tolerable safety relative to placebo among 35 Japanese patients with TSC-associated refractory seizures, consistent with the results of overall EXIST-3 study involving 366 patients. A favorable trend towards the improvement of ASD symptoms was observed.

Metformin for Treatment of Fragile X Syndrome and Other Neurological Disorders

Fragile X syndrome (FXS) is the most frequent inherited form of intellectual disability and autism spectrum disorder. Loss of the fragile X mental retardation protein, FMRP, engenders molecular, behavioral, and cognitive deficits in FXS patients. Experiments using different animal models advanced our knowledge of the pathophysiology of FXS and led to the discovery of many targets for drug treatments. In this review, we discuss the potential of metformin, an antidiabetic drug approved by the US Food and Drug Administration, to correct core symptoms of FXS and other neurological disorders in humans. We summarize its mechanisms of action in different animal and cellular models and human diseases.

A clinical update on tuberous sclerosis complex-associated neuropsychiatric disorders (TAND)

Tuberous sclerosis complex (TSC) is associated with a wide range of behavioral, psychiatric, intellectual, academic, neuropsychological, and psychosocial difficulties, which are often underdiagnosed and undertreated. Here, we present a clinical update on TSC-associated neuropsychiatric disorders, abbreviated as "TAND," to guide screening, diagnosis, and treatment in practice. The review is aimed at clinical geneticists, genetic counselors, pediatricians, and all generalists involved in the assessment and treatment of children, adolescents and adults with TSC, and related disorders. The review starts with a summary of the construct and levels of TAND, before presenting up-to-date information about each level of investigation. The review concludes with a synopsis of current and future TAND research.

Surgery for subependymal giant cell astrocytomas in children with tuberous sclerosis complex

OBJECTIVE

Subependymal giant cell astrocytomas (SEGAs) are low-grade intraventricular glial tumors that develop in 10-15% of patients with tuberous sclerosis complex; they often cause hydrocephalus and are potentially accessible to a surgical treatment. Our aim is to evaluate morbidity and results after surgery in symptomatic and asymptomatic patients.

METHOD

We present a retrospective series of 18 pediatric patients operated on for SEGA between 2006 and 2016 at our institution. We reviewed surgical indications, preoperative clinical and radiologic data, surgical management, and clinical and radiological follow-up.

RESULTS

Mean age at surgery was 10.7 years. The surgical decision was based on clinical signs of raised intracranial pressure due to hydrocephalus in 8 and on radiological findings without any clinical signs in the other 10 patients (increased in SEGA volume with or without ventricular enlargement). Surgical treatment consisted in a frontal trans-ventricular microsurgical approach in 17 patients and an endoscopic approach in 1. External ventricular drainage was placed in all the patients but 1. Ventriculoperitoneal shunting (VPS) became necessary in 6 patients, all of them presenting with a preoperative active hydrocephalus. Morbidity appeared very low with meningitis occurring in 1 patient. Resection was complete in 15 children with no recurrence during a mean follow-up of 5.25 years and incomplete in 3 requiring a second surgery.

CONCLUSION

Surgery of SEGA represents a very effective treatment with low morbidity and no mortality in the present series. In patients operated before the onset of clinical signs of hydrocephalus, internal VPS could be avoided whereas in others, an additional shunt surgery became necessary. This gives arguments in favor of a regular MRI surveillance in tuberous sclerosis complex patients with SEGA in order to best propose resective surgery once a growth of tumor and/or ventricular size have been confirmed but before raised intracranial pressure occurs.

Refractory epilepsy in preschool children with tuberous sclerosis complex: Early surgical treatment and outcome

PURPOSE

Epilepsy surgery has been shown to be effective in treating focal epilepsy related to tuberous sclerosis complex (TSC). We analyzed the advantage of early surgical management in terms of seizure frequency and development.

METHOD

We retrospectively studied the 15 patients younger than 6 years who underwent resective surgery between 2006 and 2016. Fourteen of them had invasive monitoring while the 15th was operated on under corticography.

RESULTS

Epilepsy began before 5 months of age in all patients. Overall 13 patients (86%) had a dramatic improvement of epilepsy after surgery (Engel 1 and 2) including 9 patients (60%) seizure free (Engel 1 A). In the group of 9 patients younger than 20 months at the time of surgery who presented with catastrophic epilepsies, 77% are Engel 1 A and the other 23% Engel 2. In this subpopulation, no one developed autism and four (44%) regained normal development.

CONCLUSIONS

In early onset epilepsies associated with TSC, surgical treatment is highly effective, in particular when performed early. Invasive monitoring contributes to the successful outcome. Those data have to be confirmed by multicentric studies including quantitative analyses of the recordings.

Dendritic spine actin cytoskeleton in autism spectrum disorder

Dendritic spines are small actin-rich protrusions from neuronal dendrites that form the postsynaptic part of most excitatory synapses. Changes in the shape and size of dendritic spines correlate with the functional changes in excitatory synapses and are heavily dependent on the remodeling of the underlying actin cytoskeleton. Recent evidence implicates synapses at dendritic spines as important substrates of pathogenesis in neuropsychiatric disorders, including autism spectrum disorder (ASD). Although synaptic perturbations are not the only alterations relevant for these diseases, understanding the molecular underpinnings of the spine and synapse pathology may provide insight into their etiologies and could reveal new drug targets. In this review, we will discuss recent findings of defective actin regulation in dendritic spines associated with ASD.

Cortical dysplasia and autistic trait severity in children with Tuberous Sclerosis Complex: a clinical epidemiological study

Tuberous Sclerosis Complex (TSC) is characterized by a high prevalence of autism spectrum disorders (ASD). Little is known about the relation between cortical dysplasia and ASD severity in TSC. We assessed ASD severity (using the Autism Diagnostic Observation Scale), tuber and radial migration line (RML) count and location, and cognitive functioning in 52 children with TSC and performed regression and mediation analyses. Tuber and RML count were strongly positively related to ASD severity. However, when correcting for cognitive functioning, the majority of associations became insignificant and only total tuber count remained associated to the severity of restricted/repetitive behaviors. Occipital RML count remained associated with overall ASD severity, and social communication/interaction deficit severity specifically. This study shows the important explanatory role of cognitive functioning in the association between cortical dysplasia and ASD severity, and the relevance of separately studying the two ASD subdomains.

New insights into the pathogenesis and prevention of tuberous sclerosis-associated neuropsychiatric disorders (TAND)

Tuberous sclerosis complex (TSC) is a multi-system disorder resulting from mutations in either the TSC1 or TSC2 genes leading to hyperactivation of mechanistic target of rapamycin (mTOR) signaling. TSC is commonly associated with autism (61%), intellectual disability (45%), and behavioral, psychiatric, intellectual, academic, neuropsychological, and psychosocial difficulties that are collectively referred to as TSC-associated neuropsychiatric disorders (TAND). More than 90% of children with TSC have epilepsy, including infantile spasms, and early onset of seizures, especially infantile spasms, is associated with greater impairment in intellectual development compared with individuals with TSC without seizures. Development of the mTOR inhibitors everolimus and sirolimus has led to considerable progress in the treatment of renal angiomyolipomata, pulmonary lymphangioleiomyomatosis, and subependymal giant cell astrocytomas in the brain. However, similar therapeutic progress is needed in the treatment of TAND.

Beneficial Effects of Everolimus on Autism and Attention-Deficit/Hyperactivity Disorder Symptoms in a Group of Patients with Tuberous Sclerosis Complex

OBJECTIVES

Such neuropsychiatric symptoms as autism spectrum disorders, attention-deficit/hyperactivity disorder (ADHD), intellectual disability, aggression, and epilepsy are very common in patients with tuberous sclerosis complex (TSC). Everolimus, a mammalian target of rapamycin (mTOR) inhibitor, is a recent and effective treatment for TSC patients with giant cell astrocytomas and renal angiomyolipoma, and it has been shown to have a potential to reduce tumor volume. However, there is a paucity of studies on the effects of everolimus on neuropsychiatric symptoms. The aim of the present study is to describe the effects of everolimus on emotional and behavioral symptoms and refractory epilepsy in a group of patients with TSC.

METHODS

Four boys and two girls (median age 16.5; range 7.5-23 years) were included in the study. Information on the clinical and treatment characteristics of the patients was gathered from the medical records.

RESULTS

Median everolimus dose was 10 mg/day (range 5-20 mg) and median time for follow-up was 17.5 (range 7-26) months. The drug was well tolerated with mild adverse effects, including stomatitis (three cases), increase in triglycerides and cholesterol (two cases), and constipation (one case). The adverse effects encountered during the course of treatment did not make it necessary to discontinue the drug or decrease its dose. All cases experienced very good to moderate response for controlling epileptic seizures. Besides, improvements in social contact, language, repetitive behavior, inattention, hyperactivity, and depression were observed in some patients.

CONCLUSIONS

Everolimus was well tolerated without severe adverse effects. It was helpful in controlling seizures and additional improvements were noted in autistic, ADHD, and depressive symptoms.

Risk factors for the development of autism spectrum disorder in children with tuberous sclerosis complex: protocol for a systematic review

BACKGROUND

Tuberous sclerosis complex (TSC) is an autosomal dominant condition, caused by mutations in either the TSC1 or TSC2 gene. It has widespread systemic manifestations and is associated with significant neurological morbidity. In addition to seizures and cerebral pathology including cortical tubers, subependymal nodules, subependymal giant cell astrocytoma and abnormal white matter, there are recognised neuropsychiatric difficulties including intellectual disability, autism spectrum disorder (ASD) and a range of learning and behaviour problems, recently conceptualised as "tuberous sclerosis-associated neuropsychiatric disorders", or "TAND". ASD in TSC is of particular importance because (1) it affects up to 50% of people with TSC and is a source of considerable difficulty for them and their families and (2) it provides a model for considering neurobiological pathways involved in ASD. Multiple factors are implicated in the development of ASD in TSC, including (1) seizures and related electrophysiological factors, (2) cerebral pathology, (3) genotype and (4) child characteristics. However, the neurobiological pathway remains unclear. We will conduct a systematic review to investigate and synthesise existing evidence about the role of these risk factors, individually and in combination, in leading to the development of ASD.

METHODS

Our review will report on all studies that include one or more of four predefined risk factors in the development of ASD in children with TSC. We will search five databases: MEDLINE, EMBASE, PubMed, The Cochrane Library and Web of Science (Conference Proceedings Citation Index). Studies will be selected for reporting after two authors independently (1) review all titles and abstracts, (2) read full text of all appropriate papers and (3) assess for bias using the Newcastle-Ottawa Scale recommended by the Guidelines for Meta-Analysis and Systematic Reviews of Observational Studies (MOOSE guidelines) and the ROBINS-I.

DISCUSSION

To our knowledge, this is the first systematic review investigating multiple risk factors in the development of ASD in children with TSC. Clarifying the evidence in this area will be important to researchers in the field and to clinicians providing prognostic information to families.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42016042841.

Symptom profiles of autism spectrum disorder in tuberous sclerosis complex

OBJECTIVE

To determine the extent to which deficits associated with autism spectrum disorder (ASD) in toddlers with tuberous sclerosis complex (TSC) overlap with those in toddlers with nonsyndromic ASD (nsASD) and to examine cognitive function and epilepsy severity in toddlers with TSC and comorbid ASD. This is the endpoint analysis from a longitudinal investigation of ASD risk factors in children with TSC.

METHODS

Measures included the Autism Diagnostic Observation Schedule (ADOS), the Mullen Scales of Early Learning, and clinical epilepsy variables. A repeated-measures analysis of variance was performed with between-subjects factor of group (typically developing, TSC/no ASD, TSC/ASD, nsASD) and within-subjects factors of individual ADOS item scores in the social communication and repetitive behavior/restricted interest domains. Within the TSC group, comparisons of epilepsy characteristics and cognitive domains were performed using independent-samples t tests.

RESULTS

Children with TSC/ASD demonstrated a profile of social communication impairment that had complete convergence with nsASD. Measured social communication impairments included gestures, pointing, eye contact, responsive social smile, and shared enjoyment. This convergence was observed despite the high comorbidity between ASD and cognitive impairment in TSC.

CONCLUSIONS

This study supports the clinical diagnosis of ASD in young children with TSC and demonstrates remarkable convergence of autism symptoms between TSC/ASD and nsASD. Our results strongly suggest the need for early intervention in toddlers with TSC, with treatment strategies targeting social communication function as well as broader developmental domains, before the onset of autism symptoms.

Advances in Tuberous Sclerosis Complex (TSC) research

Purpose

– The purpose of this paper is to provide a brief, descriptive overview of Tuberous Sclerosis Complex (TSC) research with particular reference to studies on Autism Spectrum Disorder (ASD).

Design/methodology/approach

– A search of electronic databases was carried out to identify English language articles on TSC. The literature was explored in more detail with a focus on neurodevelopmental disorders associated with TSC such as ASD.

Findings

– The review included 3,679 references. The earliest articles identified were published in the early twentieth century. Since then research on TSC has advanced rapidly and is being carried out worldwide. Just 62 studies have focused on ASD in TSC, although the number of publications is increasing over time.

Research limitations/implications

– More research on ASD in TSC is needed to benefit those affected by TSC and the broader ASD scientific community.

Practical implications

– Practitioners working with children and adults with ASD should be aware of the wider health issues experienced by those with genetic conditions such as TSC. Similarly, clinicians working with those who have TSC should be aware of the high prevalence of ASD in the group and implications for the way they work with their patients.

Originality/value

– This is the first paper to map and characterise the scientific literature on TSC. There remains a focus on the biomedical aspects of TSC with fewer studies on psychosocial/educational or family impacts. The review concludes with recommended research questions for the future.

Visual Evoked Potentials as a Readout of Cortical Function in Infants With Tuberous Sclerosis Complex

Tuberous sclerosis complex is an autosomal dominant genetic disorder that confers a high risk for neurodevelopmental disorders, such as autism spectrum disorder and intellectual disability. Studies have demonstrated specific delays in visual reception skills that may predict the development of autism spectrum disorder and intellectual disability. Based on evidence for alterations in the retinogeniculate pathway in animal models of tuberous sclerosis complex, we asked whether children with tuberous sclerosis complex demonstrate alterations in early visual processing that may undermine the development of higher-level visual behaviors. Pattern-reversal visual evoked potentials were recorded in infants with tuberous sclerosis complex (n = 16) and typically developing infants (n = 18) at 12 months of age. Infants with tuberous sclerosis complex demonstrated remarkably intact visual evoked potentials even within the context of intellectual disability and epilepsy. Infants with tuberous sclerosis complex show intact visual cortical processing, suggesting that delays in visually mediated behaviors in tuberous sclerosis complex may not be rooted in early visual processing deficits.

Behavioral phenotypes of genetic mouse models of autism

More than a hundred de novo single gene mutations and copy-number variants have been implicated in autism, each occurring in a small subset of cases. Mutant mouse models with syntenic mutations offer research tools to gain an understanding of the role of each gene in modulating biological and behavioral phenotypes relevant to autism. Knockout, knockin and transgenic mice incorporating risk gene mutations detected in autism spectrum disorder and comorbid neurodevelopmental disorders are now widely available. At present, autism spectrum disorder is diagnosed solely by behavioral criteria. We developed a constellation of mouse behavioral assays designed to maximize face validity to the types of social deficits and repetitive behaviors that are central to an autism diagnosis. Mouse behavioral assays for associated symptoms of autism, which include cognitive inflexibility, anxiety, hyperactivity, and unusual reactivity to sensory stimuli, are frequently included in the phenotypic analyses. Over the past 10 years, we and many other laboratories around the world have employed these and additional behavioral tests to phenotype a large number of mutant mouse models of autism. In this review, we highlight mouse models with mutations in genes that have been identified as risk genes for autism, which work through synaptic mechanisms and through the mTOR signaling pathway. Robust, replicated autism-relevant behavioral outcomes in a genetic mouse model lend credence to a causal role for specific gene contributions and downstream biological mechanisms in the etiology of autism.

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.

Inhibition of Group I Metabotropic Glutamate Receptors Reverses Autistic-Like Phenotypes Caused by Deficiency of the Translation Repressor eIF4E Binding Protein 2

Exacerbated mRNA translation during brain development has been linked to autism spectrum disorders (ASDs). Deletion of the eukaryotic initiation factor 4E (eIF4E)-binding protein 2 gene (Eif4ebp2), encoding the suppressor of mRNA translation initiation 4E-BP2, leads to an imbalance in excitatory-to-inhibitory neurotransmission and ASD-like behaviors. Inhibition of group I metabotropic glutamate receptors (mGluRs) mGluR1 and mGluR5 reverses the autistic phenotypes in several ASD mouse models. Importantly, these receptors control synaptic physiology via activation of mRNA translation. We investigated the potential reversal of autistic-like phenotypes in Eif4ebp2(-/-) mice by using antagonists of mGluR1 (JNJ16259685) or mGluR5 (fenobam). Augmented hippocampal mGluR-induced long-term depression (LTD; or chemically induced mGluR-LTD) in Eif4ebp2(-/-) mice was rescued by mGluR1 or mGluR5 antagonists. While rescue by mGluR5 inhibition occurs through the blockade of a protein synthesis-dependent component of LTD, normalization by mGluR1 antagonists requires the activation of protein synthesis. Synaptically induced LTD was deficient in Eif4ebp2(-/-) mice, and this deficit was not rescued by group I mGluR antagonists. Furthermore, a single dose of mGluR1 (0.3 mg/kg) or mGluR5 (3 mg/kg) antagonists in vivo reversed the deficits in social interaction and repetitive behaviors (marble burying) in Eif4ebp2(-/-) mice. Our results demonstrate that Eif4ebp2(-/-) mice serve as a relevant model to test potential therapies for ASD symptoms. In addition, we provide substantive evidence that the inhibition of mGluR1/mGluR5 is an effective treatment for physiological and behavioral alterations caused by exacerbated mRNA translation initiation.

SIGNIFICANCE STATEMENT

Exacerbated mRNA translation during brain development is associated with several autism spectrum disorders (ASDs). We recently demonstrated that the deletion of a negative regulator of mRNA translation initiation, the eukaryotic initiation factor 4E-binding protein 2, leads to ASD-like behaviors and increased excitatory synaptic activity. Here we demonstrated that autistic behavioral and electrophysiological phenotypes can be treated in adult mice with antagonists of group I metabotropic glutamate receptors (mGluRs), which have been previously used in other ASD models (i.e., fragile X syndrome). These findings support the use of group I mGluR antagonists as a potential therapy that extends to autism models involving exacerbated mRNA translation initiation.

Neurological and neuropsychiatric aspects of tuberous sclerosis complex

Tuberous sclerosis (also known as tuberous sclerosis complex [TSC]) is a multisystem genetic disorder that affects almost every organ in the body. Mutations in the TSC1 or TSC2 genes lead to disruption of the TSC1-TSC2 intracellular protein complex, causing overactivation of the mammalian target of rapamycin (mTOR) protein complex. The surveillance and management guidelines and clinical criteria for tuberous sclerosis were revised in 2012, and mTOR inhibitors are now recommended as treatment options for subependymal giant cell astrocytomas and renal angiomyolipomas-two common features of the disease. However, most morbidity and mortality caused by tuberous sclerosis is associated with neurological and neuropsychiatric manifestations. Treatment of epilepsy associated with tuberous sclerosis remains a major challenge, with more than 60% of patients having ongoing seizures. Tuberous-sclerosis-associated neuropsychiatric disorders (TAND) are multilevel and occur in most individuals with the disorder, but are rarely assessed and treated. Clinical trials of mTOR inhibitors to treat seizures and TAND are underway. Management of the neurological and neuropsychiatric manifestations of the disorder should be coordinated with treatment of other organ systems. In view of the age-related expression of manifestations from infancy to adulthood, continuity of clinical care and ongoing monitoring is paramount, and particular attention is needed to plan transition of patient care from childhood to adult services.

Autistic spectrum disorders: A review of clinical features, theories and diagnosis

Autism spectrum disorder (ASD) is a set of neurodevelopmental disorders that is among the most severe in terms of prevalence, morbidity and impact to the society. It is characterized by complex behavioral phenotype and deficits in both social and cognitive functions. Although the exact cause of ASD is still not known, the main findings emphasize the role of genetic and environmental factors in the development of autistic behavior. Environmental factors are also likely to interact with the genetic profile and cause aberrant changes in brain growth, neuronal development, and functional connectivity. The past few years have seen an increase in the prevalence of ASD, as a result of enhanced clinical tests and diagnostic tools. Despite growing evidence for the involvement of endogenous biomarkers in the pathophysiology of ASD, early detection of this disorder remains a big challenge. This paper describes the main behavioral and cognitive features of ASD, as well as the symptoms that differentiate autism from other developmental disorders. An attempt will be made to integrate all the available evidence which point to reduced brain connectivity, mirror neurons deficits, and inhibition-excitation imbalance in individuals with ASD. Finally, this review discusses the main factors involved in the pathophysiology of ASD, and illustrates some of the most important markers used for the diagnosis of this debilitating disorder.

Dendritic spine dysgenesis in autism related disorders

The activity-dependent structural and functional plasticity of dendritic spines has led to the long-standing belief that these neuronal compartments are the subcellular sites of learning and memory. Of relevance to human health, central neurons in several neuropsychiatric illnesses, including autism related disorders, have atypical numbers and morphologies of dendritic spines. These so-called dendritic spine dysgeneses found in individuals with autism related disorders are consistently replicated in experimental mouse models. Dendritic spine dysgenesis reflects the underlying synaptopathology that drives clinically relevant behavioral deficits in experimental mouse models, providing a platform for testing new therapeutic approaches. By examining molecular signaling pathways, synaptic deficits, and spine dysgenesis in experimental mouse models of autism related disorders we find strong evidence for mTOR to be a critical point of convergence and promising therapeutic target.

Synapses as therapeutic targets for autism spectrum disorders: an international symposium held in pavia on july 4th, 2014

New progresses into the molecular and cellular mechanisms of autism spectrum disorders (ASDs) have been discussed in 1 day international symposium held in Pavia (Italy) on July 4th, 2014 entitled "synapses as therapeutic targets for autism spectrum disorders" (satellite of the FENS Forum for Neuroscience, Milan, 2014). In particular, world experts in the field have highlighted how animal models of ASDs have greatly advanced our understanding of the molecular pathways involved in synaptic dysfunction leading sometimes to "synaptic clinical trials" in children.

Early developmental trajectories associated with ASD in infants with tuberous sclerosis complex

OBJECTIVE

We performed a longitudinal cohort study of infants with tuberous sclerosis complex (TSC), with the overarching goal of defining early clinical, behavioral, and biological markers of autism spectrum disorder (ASD) in this high-risk population.

METHODS

Infants with TSC and typically developing controls were recruited as early as 3 months of age and followed longitudinally until 36 months of age. Data gathered at each time point included detailed seizure history, developmental testing using the Mullen Scales of Early Learning, and social-communication assessments using the Autism Observation Scale for Infants. At 18 to 36 months, a diagnostic evaluation for ASD was performed using the Autism Diagnostic Observation Schedule.

RESULTS

Infants with TSC demonstrated delays confined to nonverbal abilities, particularly in the visual domain, which then generalized to more global delays by age 9 months. Twenty-two of 40 infants with TSC were diagnosed with ASD. Both 12-month cognitive ability and developmental trajectories over the second and third years of life differentiated the groups. By 12 months of age, the ASD group demonstrated significantly greater cognitive delays and a significant decline in nonverbal IQ from 12 to 36 months.

CONCLUSIONS

This prospective study characterizes early developmental markers of ASD in infants with TSC. The early delay in visual reception and fine motor ability in the TSC group as a whole, coupled with the decline in nonverbal ability in infants diagnosed with ASD, suggests a domain-specific pathway to ASD that can inform more targeted interventions for these high-risk infants.

Common variants in genes of the postsynaptic FMRP signalling pathway are risk factors for autism spectrum disorders

Autism spectrum disorders (ASD) are heterogeneous disorders with a high heritability and complex genetic architecture. Due to the central role of the fragile X mental retardation gene 1 protein (FMRP) pathway in ASD we investigated common functional variants of ASD risk genes regulating FMRP. We genotyped ten SNPs in two German patient sets (N = 192 and N = 254 families, respectively) and report association for rs7170637 (CYFIP1; set 1 and combined sets), rs6923492 (GRM1; combined sets), and rs25925 (CAMK4; combined sets). An additional risk score based on variants with an odds ratio (OR) >1.25 in set 1 and weighted by their respective log transmitted/untransmitted ratio revealed a significant effect (OR 1.30, 95 % CI 1.11-1.53; P = 0.0013) in the combined German sample. A subsequent meta-analysis including the two German samples, the "Strict/European" ASD subsample of the Autism Genome Project (1,466 families) and a French case/control (541/366) cohort showed again association of rs7170637-A (OR 0.85, 95 % CI 0.75-0.96; P = 0.007) and rs25925-G (OR 1.31, 95 % CI 1.04-1.64; P = 0.021) with ASD. Functional analyses revealed that these minor alleles predicted to alter splicing factor binding sites significantly increase levels of an alternative mRNA isoform of the respective gene while keeping the overall expression of the gene constant. These findings underpin the role of ASD candidate genes in postsynaptic FMRP regulation suggesting that an imbalance of specific isoforms of CYFIP1, an FMRP interaction partner, and CAMK4, a transcriptional regulator of the FMRP gene, modulates ASD risk. Both gene products are related to neuronal regulation of synaptic plasticity, a pathomechanism underlying ASD and may thus present future targets for pharmacological therapies in ASD.

Is mTOR inhibition a systemic treatment for tuberous sclerosis?

Tuberous sclerosis complex (TSC) is a genetic multisystem disorder characterized by the development of hamartomas in several organs. Mutations in the TSC1 and TSC2 tumor suppressor genes determin overactivation of the mammalian target of rapamycin (mTOR) signaling pathway and subsequent abnormalities in numerous cell processes. As a result, mTOR inhibitors such as sirolimus and everolimus have the potential to provide targeted therapy for TSC patients. Everolimus has been recently approved as a pharmacotherapy option for TSC patients with subependymal giant-cell astrocytomas (SEGAs) or renal angiomyolipomas (AMLs). However, clinical evidence suggests that this treatment can benefit other TSC-associated disease manifestations, such as skin manifestations, pulmonary lymphangioleiomyomatosis, cardiac rhabdomyomas, and epilepsy. Therefore, the positive effects that mTOR inhibition have on a wide variety of TSC disease manifestations make this a potential systemic treatment option for this genetic multifaceted disorder.

Autism genetics

Autism spectrum disorder (ASD) is a severe neuropsychiatric disease with strong genetic underpinnings. However, genetic contributions to autism are extremely heterogeneous, with many different loci underlying the disease to a different extent in different individuals. Moreover, the phenotypic expression (i.e., "penetrance") of these genetic components is also highly variable, ranging from fully penetrant point mutations to polygenic forms with multiple gene-gene and gene-environment interactions. Furthermore, many genes involved in ASD are also involved in intellectual disability, further underscoring their lack of specificity in phenotypic expression. We shall hereby review current knowledge on the genetic basis of ASD, spanning genetic/genomic syndromes associated with autism, monogenic forms due to copy number variants (CNVs) or rare point mutations, mitochondrial forms, and polygenic autisms. Finally, the recent contributions of genome-wide association and whole exome sequencing studies will be highlighted.

Autism spectrum disorders: the quest for genetic syndromes

Autism spectrum disorders (ASD) are a heterogeneous group of neurodevelopmental disabilities with various etiologies, but with a heritability estimate of more than 90%. Although the strong correlation between autism and genetic factors has been long established, the exact genetic background of ASD remains unclear. A number of genetic syndromes manifest ASD at higher than expected frequencies compared to the general population. These syndromes account for more than 10% of all ASD cases and include tuberous sclerosis, fragile X, Down, neurofibromatosis, Angelman, Prader-Willi, Williams, Duchenne, etc. Clinicians are increasingly required to recognize genetic disorders in individuals with ASD, in terms of providing proper care and prognosis to the patient, as well as genetic counseling to the family. Vice versa, it is equally essential to identify ASD in patients with genetic syndromes, in order to ensure correct management and appropriate educational placement. During investigation of genetic syndromes, a number of issues emerge: impact of intellectual disability in ASD diagnoses, identification of autistic subphenotypes and differences from idiopathic autism, validity of assessment tools designed for idiopathic autism, possible mechanisms for the association with ASD, etc. Findings from the study of genetic syndromes are incorporated into the ongoing research on autism etiology and pathogenesis; different syndromes converge upon common biological backgrounds (such as disrupted molecular pathways and brain circuitries), which probably account for their comorbidity with autism. This review paper critically examines the prevalence and characteristics of the main genetic syndromes, as well as the possible mechanisms for their association with ASD.

Resource utilization in children with tuberous sclerosis complex and associated seizures: a retrospective chart review study

Seizures are a hallmark manifestation of tuberous sclerosis complex, yet data characterizing resource utilization are lacking. This retrospective chart review was performed to assess the economic burden of tuberous sclerosis complex with neurologic manifestations. Demographic and resource utilization data were collected for 95 patients for up to 5 years after tuberous sclerosis complex diagnosis. Mean age at diagnosis was 3.1 years, with complex partial and infantile spasms as the most common seizure types. In the first 5 years post-diagnosis, 83.2% required hospitalization, 30.5% underwent surgery, and the majority of patients (90.5%) underwent ≥3 testing procedures. In 79 patients with a full 5 years of data, hospitalizations, intensive care unit stays, diagnostic testing, and rehabilitation services decreased over the 5-year period. Resource utilization is cost-intensive in children with tuberous sclerosis complex and associated seizures during the first few years following diagnosis. Improving seizure control and reducing health care costs in this population remain unmet needs.

A circuitry and biochemical basis for tuberous sclerosis symptoms: from epilepsy to neurocognitive deficits

Tuberous sclerosis complex (TSC) is an autosomal dominant monogenetic disorder that is characterized by the formation of benign tumors in several organs as well as brain malformations and neuronal defects. TSC is caused by inactivating mutations in one of two genes, TSC1 and TSC2, resulting in increased activity of the mammalian Target of Rapamycin (mTOR). Here, we explore the cytoarchitectural and functional CNS aberrations that may account for the neurological presentations of TSC, notably seizures, hydrocephalus, and cognitive and psychological impairments. In particular, recent mouse models of brain lesions are presented with an emphasis on using electroporation to allow the generation of discrete lesions resulting from loss of heterozygosity during perinatal development. Cortical lesions are thought to contribute to epileptogenesis and worsening of cognitive defects. However, it has recently been suggested that being born with a mutant allele without loss of heterozygosity and associated cortical lesions is sufficient to generate cognitive and neuropsychiatric problems. We will thus discuss the function of mTOR hyperactivity on neuronal circuit formation and the potential consequences of being born heterozygous on neuronal function and the biochemistry of synaptic plasticity, the cellular substrate of learning and memory. Ultimately, a major goal of TSC research is to identify the cellular and molecular mechanisms downstream of mTOR underlying the neurological manifestations observed in TSC patients and identify novel therapeutic targets to prevent the formation of brain lesions and restore neuronal function.

Behavioral assessment of Japanese children with epilepsy using SDQ (strengths and difficulties questionnaire)

The aim of this study was to elucidate the availability of the strengths and difficulties questionnaire (SDQ) as a screening tool for identifying behavioral problems in Japanese children with epilepsy.

METHODS

Eighty-three 4-16 year-old epileptic patients, followed at Tanabe-Kadobayashi Children's Clinic, were studied. Children with severe mental or physical disability were excluded. The Japanese version of the SDQ was used, and scores were compared to the Japanese standard.

RESULTS

'Hyperactivity' was the SDQ category with the most striking differences from normal: a significant numbers of children had scores above the clinically normal range and only a small proportion were within the normal range (p<0.0001). The rates of epilepsy patients with scores above normal range were also significantly higher for 'peer problems' and 'conduct problems' (p<0.0001 and p<0.01). The rates of epilepsy patients with scores within the normal range was significantly lower for 'emotional symptoms' than in normal controls (p<0.001). On the other hand, the 'pro-social behavior' score did not differ significantly from the Japanese standard. As for clinical factors, patients with symptomatic localization-related epilepsy and focal electroencephalographic abnormalities had significantly higher scores for some SDQ items. Age at epilepsy onset correlated negatively with scores for 'total difficulties' and 'hyperactivity', suggesting early onset to be a risk factor for poor SDQ scores.

CONCLUSIONS

These findings confirm that higher rates of psychiatric comorbidity in Japanese children with epilepsy may be diagnosed using SDQ in Japanese children with epilepsy. These problems should be addressed in the early phase of epilepsy management in order to preserve health-related quality of life for affected patients.

Loss of Tsc2 in Purkinje cells is associated with autistic-like behavior in a mouse model of tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is a dominant tumor suppressor disorder caused by mutations in either TSC1 or TSC2. TSC causes substantial neuropathology, often leading to autism spectrum disorders (ASDs) in up to 60% of patients. The anatomic and neurophysiologic links between these two disorders are not well understood. We have generated and characterized a novel TSC mouse model with Purkinje cell specific Tsc2 loss. These Tsc2f/-;Cre mice exhibit progressive Purkinje cell degeneration. Since loss of Purkinje cells is a well reported postmortem finding in patients with ASD, we conducted a series of behavior tests to asses if Tsc2f/-;Cre mice displayed autistic-like deficits. Tsc2f/-;Cre mice demonstrated increased repetitive behavior as assessed with marble burying activity. Using the three chambered apparatus to asses social behavior, we found that Tsc2f/-;Cre mice showed behavioral deficits, exhibiting no preference between a stranger mouse and an inanimate object, or between a novel and a familiar mouse. We also detected social deficits in Tsc2f/f;Cre mice, suggesting that Purkinje cell pathology is sufficient to induce ASD-like behavior. Importantly, social behavior deficits were prevented with rapamycin treatment. Altogether, these results demonstrate that loss of Tsc2 in Purkinje cells in a Tsc2-haploinsufficient background leads to autistic-like behavioral deficits. These studies provide compelling evidence that Purkinje cell loss and/or dysfunction may be an important link between TSC and ASD as well as a general anatomic phenomenon that contributes to the ASD phenotype.

Autism spectrum disorder in a child with propionic acidemia

Autism is a neurodevelopmental disorder characterized by a combination of reciprocal social deficits, communication impairment, and rigid ritualistic interests. While autism does not have an identifying cause in most of the cases, it is associated with known medical conditions in at least 10% of cases. Although uncommon, cases of autism have also been reported in association with metabolic disorders. In this brief report, we describe the occurrence of autism in a 7-year-old girl with propionic acidemia (PA), a common form of organic aciduria resulting from the deficiency of propionyl-CoA carboxylase and characterized by frequent and potentially lethal episodes of metabolic acidosis often accompanied by hyperammonemia. It is particularly common in countries with high rates of consanguinity. Early diagnosis of autism in patients with metabolic disorders is important since autistic features are sometimes the most disruptive of all the child's problems. This facilitates providing the needed behavioral services not otherwise available for children with metabolic disorders.

Epilepsy in Tuberous Sclerosis Complex

Tuberous Sclerosis Complex (TSC) is an autosomal dominant multisystem disorder, characterized by the presence of hamartomatous lesions involving different organ systems, including the brain. Epilepsy is the most common presenting symptom, representing a major source of morbidity and mortality. Despite multiple antiepileptic drug combinations, in about two thirds of cases the patients present high-frequency drug-resistant epilepsy, and nonpharmacologic options may be considered. The aim of this work was to point out the current knowledge on epileptogenesis in TSC, the available medical therapies and diagnostic tools, and possible surgical strategies, with the intent to better understand the actual difficulties in controlling seizures and the results reported in the literature. There is also a section dedicated to the common association with cognitive impairment and the role of epilepsy control on its outcome.

Autism and cancer risk

A literature review was conducted on the genetic and developmental bases of autism in relation to genes and pathways associated with cancer risk. Convergent lines of evidence from four types of analysis: (1) recent theoretical studies on the causes of autism, (2) epidemiological studies, (3) genetic analyses linking autism with mutations in tumor suppressor genes and other cancer-associated genes and pathways, and (4) contrasts with schizophrenia, Parkinson's, and Alzheimer's disease indicate that autism may involve altered cancer risk. This evidence should motivate further epidemiological studies, and it provides useful insights into the nature of the genetic, epigenetic, and environmental factors underlying the etiologies of autism, other neurological conditions, and carcinogenesis.