Tuberous Sclerosis Complex-Associated Neuropsychiatric Disorders (TAND): New Findings on Age, Sex, and Genotype in Relation to Intellectual Phenotype

Autism Spectrum Disorder Symptom Profiles in Fragile X Syndrome, Angelman Syndrome, Tuberous Sclerosis Complex and Neurofibromatosis Type 1

Studying Autism Spectrum Disorder (ASD) heterogeneity in biologically homogeneous samples may increase our knowledge of ASD etiology. Fragile X syndrome (FXS), Angelman syndrome (AS), Tuberous Sclerosis Complex (TSC), and Neurofibromatosis type 1 (NF1) are monogenic disorders with high a prevalence of ASD symptomatology. This study aimed to identify ASD symptom profiles in a large group of children and adolescents (0;9-28 years) with FXS, AS, TSC, and NF1. Data on ASD symptomatology (Autism Diagnostic Observation Scale (ADOS-2) & Social Responsiveness Scale (SRS-2)) were collected from children and adolescents with FXS (n = 54), AS (n = 93), TSC (n = 112), and NF1 (n = 278). To identify groups of individuals with similar ASD profiles, we performed two latent profile analyses. We identified a four-profile model based on the ADOS-2, with a (1) 'Non-spectrum symptom profile', (2) 'Social Affect symptom profile', (3)'Restricted/Repetitive Behaviors symptom profile', and (4)'ASD symptom profile'. We also identified a four-profile model based on the SRS, with a (1)'Non-clinical symptom profile', (2)'Mild symptom profile', (3)'Moderate symptom profile', and (4)'Severe symptom profile'. Although each syndrome group exhibited varying degrees of severity, they also displayed heterogeneity in the profiles in which they were classified. We found distinct ASD symptom profiles in a population consisting of children and adolescents with FXS, AS, TSC, and NF1. Our study highlights the importance of a personalized approach to the identification and management of ASD symptoms in rare genetic syndromes. Future studies should aim to include more domains of functioning and investigate the stability of latent profiles over time.

International consensus recommendations for the identification and treatment of tuberous sclerosis complex-associated neuropsychiatric disorders (TAND)

BACKGROUND

Tuberous sclerosis complex (TSC) is associated with a wide range of physical manifestations for which international clinical recommendations for diagnosis and management have been established. TSC is, however, also associated with a wide range of TSC-Associated Neuropsychiatric Disorders (TAND) that are typically under-identified and under-treated yet associated with a profound burden of disease. The contemporary evidence base for the identification and treatment of TAND is much more limited and, to date, consensus recommendations for the diagnosis and management of TAND have also been limited and non-specific.

METHODS

The TANDem project was launched with an international, interdisciplinary, and participatory consortium of 24 individuals, including TSC family representatives, from all World Health Organization (WHO) regions but one. One of the aims of the TANDem project was to generate consensus recommendations for the identification and treatment of TAND. At the time of this project, no internationally adopted standard methodology and methodological checklists existed for the generation of clinical practice recommendations. We therefore developed our own systematic procedure for evidence review and consensus-building to generate evidence-informed consensus recommendations of relevance to the global TSC community.

RESULTS

At the heart of the consensus recommendations are ten core principles surrounded by cluster-specific recommendations for each of the seven natural TAND clusters identified in the literature (autism-like, dysregulated behavior, eat/sleep, mood/anxiety, neuropsychological, overactive/impulsive, and scholastic) and a set of wraparound psychosocial cluster recommendations. The overarching recommendation is to "screen" for TAND at least annually, to "act" using appropriate next steps for evaluation and treatment, and to "repeat" the process to ensure early identification and early intervention with the most appropriate biological, psychological, and social evidence-informed approaches to support individuals with TSC and their families.

CONCLUSIONS

The consensus recommendations should provide a systematic framework to approach the identification and treatment of TAND for health, educational, social care teams and families who live with TSC. To ensure global dissemination and implementation of these recommendations, partnerships with the international TSC community will be important. One of these steps will include the generation of a "TAND toolkit" of "what to seek" and "what to do" when difficulties are identified in TAND clusters.

Tuberous Sclerosis Complex Patients' Needs and Difficulties-Results of TAND Questionnaire Analysis in Polish Adult Population

INTRODUCTION

Tuberous Sclerosis Complex (TSC) is a rare genetic disease. Around 90% of individuals with TSC present some neuropsychiatric manifestations (TSC-associated neuropsychiatric disorders, TAND). To date, none of the studies have focused on the TAND profile of the adult population. Thus, the aim of the study was to describe their potential specific needs and difficulties, including differences in cohorts with or without epilepsy and/or intellectual disability.

METHOD

The Polish version of the TAND Checklist was used for assessment of individuals with TSC. Participants had to meet the criteria for diagnosis of TSC. One hundred adult participants (forty-eight males/ fifty-two females; mean age 32.33 ± 11.29) were enrolled in the study. Epilepsy was present in 71% of patients; intellectual disability occurred in a total of 37%.

RESULTS

Only 11% of individuals received complete TAND features examination in the past. Moreover, 91.5 of the subjects had four and more TAND symptoms. Intellectually disabled patients and those with epilepsy had more neuropsychiatric problems than epilepsy-free subjects.

CONCLUSIONS

Findings reveal that TANDs are common in adults with TSC and are underdiagnosed. Most individuals present several behavioural and cognitive problems. Among psychiatric disorders, the most common are ASD, depression, and anxiety disorder. TAND screening should be widely disseminated and applied in clinical practice for early identification, prevention, and rehabilitation of their difficulties. TAND is one of the most significant issues affecting the quality of life of TSC patients and their carers.

Tuberous sclerosis complex is a novel, amyloid-independent tauopathy associated with elevated phosphorylated 3R/4R tau aggregation

Tuberous sclerosis complex (TSC) is a neurodevelopmental disorder caused by mutations in the TSC1 and TSC2 genes and autosomal dominantly inherited. These mutations cause hyperactivation of the mammalian Target of Rapamycin (mTOR) pathway, leading to the development of nonmalignant masses involving various organ systems. Patients with TSC also experience neuropsychiatric symptoms collectively termed Tuberous Sclerosis Complex Associated Neuropsychiatric Disorder (TAND). Due to research advancements in TSC, patients now live well beyond the age of 50. Many experience objective impairment of memory and executive function, supported by formal neuropsychological testing, beginning in their late 40s. Biomarker analysis has described elevated levels of phosphorylated tau-181 in the cerebrospinal fluid of patients with TAND. Tau-PET imaging has also shown focal accumulation of the radiotracer flortaucipir (AV1451), suggesting that TSC may be a neurodegenerative disorder arising from accumulation of phosphorylated tau. However, the flortaucipir tracer has been reported to have significant off-target binding, preventing definitive conclusions from being drawn about the molecular etiology of neurodegeneration in TSC. Therefore, we initiated the Colocalization of AV1451 and Phosphorylated Tau in Adult brain tissue (CAPA) study. This study aimed to determine if flortaucipir is bound to phosphorylated tau in brains of patients with TSC and further sought to determine the specific tau isoform seen in TSC. Our results show that flortaucipir labels the 3R/4R isoform of phosphorylated tau, commonly seen in Alzheimer's disease. However, amyloid staining was negative in brains of adult patients with TSC. Therefore, we conclude that TAND symptoms are due to the accumulation of the phosphorylated tau isoform seen in Alzheimer's disease. This study suggests that hyperactivation of the mammalian Target of Rapamycin pathway may play a role in the amyloid-independent development of 3R/4R tau aggregation. Our findings could lead to a new era of anti-tau therapies used to treat both disorders.

Symptom rates and profile clustering in tuberous sclerosis complex-associated neuropsychiatric disorders (TAND)

BACKGROUND

Tuberous Sclerosis Complex (TSC) is associated with a range of neuropsychiatric difficulties, appropriately termed TSC-Associated Neuropsychiatric Disorders (TAND). The objectives of the study were to analyze the rates of TAND symptoms in a cohort of patients seen at the TSC Center of Excellence at Cincinnati Children's Hospital and to identify clinically meaningful profiles based on TAND symptoms.

METHODS

Data from the TAND Checklist was obtained from participants seen at the TSC Center of Excellence at Cincinnati Children's Hospital Medical Center from June 2015 to August 2018. Cluster and factor analyses for each TAND symptom were performed. Factor scores were then calculated for participants, and a K-means cluster analysis of these scores was used to empirically identify distinct overall TAND symptom profiles occurring in TSC.

RESULTS

A total of 1545 checklists was completed for 668 participants (37% adults and 63% children). Approximately 90% of participants reported at least one TAND symptom with an average of 12 symptoms (out of 29). Symptom rates ranged between 5 and 60%. The most common symptoms were neuropsychologic symptoms. A seven-cluster and seven-factor solution were found to be optimal. K-means cluster analysis resulted in a seven-profile solution, ranging from low to high symptom burden.

CONCLUSION

This study is the first to identify natural phenotypic profiles of TAND symptoms. Study of specific TAND subpopulations with shared profiles may facilitate better understanding of the underlying biology of TAND and better assessment of more targeted treatments.

EWAS of Monozygotic Twins Implicate a Role of mTOR Pathway in Pathogenesis of Tic Spectrum Disorder

Tic spectrum disorder (TSD) is an umbrella term which includes Gilles de la Tourette syndrome (GTS) and chronic tic disorder (CTD). They are considered highly heritable, yet the genetic components remain largely unknown. In this study we aimed to investigate disease-associated DNA methylation differences to identify genes and pathways which may be implicated in TSD aetiology. For this purpose, we performed an exploratory analysis of the genome-wide DNA methylation patterns in whole blood samples of 16 monozygotic twin pairs, of which eight were discordant and six concordant for TSD, while two pairs were asymptomatic. Although no sites reached genome-wide significance, we identified several sites and regions with a suggestive significance, which were located within or in the vicinity of genes with biological functions associated with neuropsychiatric disorders. The two top genes identified (TSC1 and CRYZ/TYW3) and the enriched pathways and components (phosphoinosides and PTEN pathways, and insulin receptor substrate binding) are related to, or have been associated with, the PI3K/AKT/mTOR pathway. Genes in this pathway have previously been associated with GTS, and mTOR signalling has been implicated in a range of neuropsychiatric disorders. It is thus possible that altered mTOR signalling plays a role in the complex pathogenesis of TSD.

Dopaminergic Dysregulation in Syndromic Autism Spectrum Disorders: Insights From Genetic Mouse Models

Autism spectrum disorder (ASD) is a neurodevelopmental disorder defined by altered social interaction and communication, and repetitive, restricted, inflexible behaviors. Approximately 1.5-2% of the general population meet the diagnostic criteria for ASD and several brain regions including the cortex, amygdala, cerebellum and basal ganglia have been implicated in ASD pathophysiology. The midbrain dopamine system is an important modulator of cellular and synaptic function in multiple ASD-implicated brain regions via anatomically and functionally distinct dopaminergic projections. The dopamine hypothesis of ASD postulates that dysregulation of dopaminergic projection pathways could contribute to the behavioral manifestations of ASD, including altered reward value of social stimuli, changes in sensorimotor processing, and motor stereotypies. In this review, we examine the support for the idea that cell-autonomous changes in dopaminergic function are a core component of ASD pathophysiology. We discuss the human literature supporting the involvement of altered dopamine signaling in ASD including genetic, brain imaging and pharmacologic studies. We then focus on genetic mouse models of syndromic neurodevelopmental disorders in which single gene mutations lead to increased risk for ASD. We highlight studies that have directly examined dopamine neuron number, morphology, physiology, or output in these models. Overall, we find considerable support for the idea that the dopamine system may be dysregulated in syndromic ASDs; however, there does not appear to be a consistent signature and some models show increased dopaminergic function, while others have deficient dopamine signaling. We conclude that dopamine dysregulation is common in syndromic forms of ASD but that the specific changes may be unique to each genetic disorder and may not account for the full spectrum of ASD-related manifestations.