Down-regulation of the brain-specific cell-adhesion molecule contactin-3 in tuberous sclerosis complex during the early postnatal period

Background The genetic disorder tuberous sclerosis complex (TSC) is frequently accompanied by the development of neuropsychiatric disorders, including autism spectrum disorder and intellectual disability, with varying degrees of impairment. These co-morbidities in TSC have been linked to the structural brain abnormalities, such as cortical tubers, and recurrent epileptic seizures (in 70–80% cases). Previous transcriptomic analysis of cortical tubers revealed dysregulation of genes involved in cell adhesion in the brain, which may be associated with the neurodevelopmental deficits in TSC. In this study we aimed to investigate the expression of one of these genes – cell-adhesion molecule contactin-3. Methods Reverse transcription quantitative polymerase chain reaction for the contactin-3 gene (CNTN3) was performed in resected cortical tubers from TSC patients with drug-resistant epilepsy (n = 35, age range: 1–48 years) and compared to autopsy-derived cortical control tissue (n = 27, age range: 0–44 years), as well as by western blot analysis of contactin-3 (n = 7 vs n = 7, age range: 0–3 years for both TSC and controls) and immunohistochemistry (n = 5 TSC vs n = 4 controls). The expression of contactin-3 was further analyzed in fetal and postnatal control tissue by western blotting and in-situ hybridization, as well as in the SH-SY5Y neuroblastoma cell line differentiation model in vitro. Results CNTN3 gene expression was lower in cortical tubers from patients across a wide range of ages (fold change = − 0.5, p < 0.001) as compared to controls. Contactin-3 protein expression was lower in the age range of 0–3 years old (fold change = − 3.8, p < 0.001) as compared to the age-matched controls. In control brain tissue, contactin-3 gene and protein expression could be detected during fetal development, peaked around birth and during infancy and declined in the adult brain. CNTN3 expression was induced in the differentiated SH-SY5Y neuroblastoma cells in vitro (fold change = 6.2, p < 0.01). Conclusions Our data show a lower expression of contactin-3 in cortical tubers of TSC patients during early postnatal period as compared to controls, which may affect normal brain development and might contribute to neuropsychiatric co-morbidities observed in patients with TSC.

Sporadic facial angiofibroma and sporadic angiomyolipoma mimicking tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is a genetic syndrome due to mutations in either TSC1 or TSC2, leading to the development of hamartomatous tumours at multiple body sites, including facial skin (facial angiofibroma (FAF)), brain (cortical tubers) and kidney (angiomyolipoma (AML)). In this report, we describe an individual with minimal TSC clinical features, who had ‘no mutation identified’ (NMI) by prior genetic testing in a clinical laboratory. Our massively parallel sequencing (MPS) analysis of multiple samples from different body sites and tumours (including blood, saliva, normal skin, AML and FAF) revealed an extraordinary situation in which FAF and AML had completely independent inactivating biallelic variants in TSC2, not present in other matched samples. This suggests that the two different lesions (AML and FAF) are not due to the same underlying germline or mosaic mutation, rather both are likely sporadic events. This case demonstrates the relevance of thorough clinical examination, high-coverage MPS of multiple tumours and matched normal tissues, and appropriate genetic counselling for individuals with marginal TSC features and possible TSC1 or TSC2 mosaicism.

Characteristics of cortical tubers in tuberous sclerosis

Туберозный склероз - орфанное аутосомно-доминантное наследственное заболевание, причиной которого являются инактивирующие мутации в генах TSC1 или TSC2, сопровождающиеся гиперактивацией сигнального пути mTOR, отвечающего за регуляцию роста, пролиферации, выживаемости клеток, а также аутофагии. Одним из основных клинических симптомов туберозного склероза является наличие туберов в головном мозге. Данные образования характеризуются нарушениями кортикальной ламинации, появлением аномальных нейронов и выраженным глиозом. Известно, что количество кортикальных туберов коррелирует с развитием нейропсихиатрических расстройств, в том числе фармакорезистентной эпилепсии. В данной статье освещены вопросы молекулярной генетики туберозного склероза, приведена гистопатологическая характеристика кортикальных туберов, рассмотрен молекулярный механизм морфогенеза кортикальных туберов, а также приведены данные о связи этих образований с развитием неврологических проявлений и методах их лечения. Tuberous sclerosis is an orphan autosomal dominant hereditary disease caused by inactivating mutations in the TSC1 or TSC2 genes, accompanied by hyperactivation of the mTOR signaling pathway, which is responsible for the regulation of growth, proliferation, cell survival, and autophagy. One of the main clinical symptoms of tuberous sclerosis is the formation of tubers in the brain. These formations are characterized by disorders of the cortical lamination, the appearance of abnormal neurons and severe gliosis. It is known that the presence of cortical tubers correlates with the development of neuropsychiatric disorders, including drug-resistant epilepsy. This article highlights the issues of molecular genetics of tuberous sclerosis, presents the histopathological characteristics of cortical tubers, considers mechanism of morphogenesis of cortical tubers, and also presents the data on relationship of these formations with the development of neurological manifestations and methods of their treatment.

Neurite Outgrowth Inhibitor (NogoA) Is Upregulated in White Matter Lesions of Complex Cortical Malformations

Complex cortical malformations (CCMs), such as hemimegalencephaly and polymicrogyria, are associated with drug-resistant epilepsy and developmental impairment. They share certain neuropathological characteristics including mammalian target of rapamycin (mTOR) activation and an atypical number of white matter neurons. To get a better understanding of the pathobiology of the lesion architecture, we investigated the role of neurite outgrowth inhibitor A (NogoA), a known regulator of neuronal migration. Epilepsy surgery specimens from 16 CCM patients were analyzed and compared with sections of focal cortical dysplasia IIB (FCD IIB, n = 22), tuberous sclerosis complex (TSC, n = 8) as well as healthy controls (n = 15). Immunohistochemistry was used to characterize NogoA, myelination, and mTOR signaling. Digital slides were evaluated automatically with ImageJ. NogoA staining showed a significantly higher expression within the white matter of CCM and FCD IIB, whereas cortical tubers presented levels similar to controls. Further analysis of possible associations of NogoA with other factors revealed a positive correlation with mTOR and seizure frequency. To identify the main expressing NogoA cell type, double staining revealed dysmorphic neuronal white matter cells. Increased NogoA expression is associated with profound inhibition of neuritic sprouting and therefore contributes to a decrease in neuronal network complexity in CCM patients.

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

Tuberous sclerosis complex (TSC) is a monogenetic disease that arises due to mutations in either the TSC1 or TSC2 gene and affects multiple organ systems. One of the hallmark manifestations of TSC are cortical malformations referred to as cortical tubers. These tubers are frequently associated with treatment-resistant epilepsy. Some of these patients are candidates for epilepsy surgery. White matter abnormalities, such as loss of myelin and oligodendroglia, have been described in a small subset of resected tubers but mechanisms underlying this phenomenon are unclear. Herein, we analyzed a variety of neuropathologic and immunohistochemical features in gray and white matter areas of resected cortical tubers from 46 TSC patients using semi-automated quantitative image analysis. We observed divergent amounts of myelin basic protein as well as numbers of oligodendroglia in both gray and white matter when compared with matched controls. Analyses of clinical data indicated that reduced numbers of oligodendroglia were associated with lower numbers on the intelligence quotient scale and that lower amounts of myelin-associated oligodendrocyte basic protein were associated with the presence of autism-spectrum disorder. In conclusion, myelin pathology in cortical tubers extends beyond the white matter and may be linked to cognitive dysfunction in TSC patients.

Cerebral organoid model reveals excessive proliferation of human caudal late interneuron progenitors in Tuberous Sclerosis Complex

SummaryAlthough the intricate and prolonged development of the human brain critically distinguishes it from other mammals1, our current understanding of neurodevelopmental diseases is largely based on work using animal models. Recent studies revealed that neural progenitors in the human brain are profoundly different from those found in rodent animal models2–5. Moreover, post-mortem studies revealed extensive migration of interneurons into the late-gestational and post-natal human prefrontal cortex that does not occur in rodents6. Here, we use cerebral organoids to show that overproduction of mid-gestational human interneurons causes Tuberous Sclerosis Complex (TSC), a severe neuro-developmental disorder associated with mutations in TSC1 and TSC2. We identify a previously uncharacterized population of caudal late interneuron progenitors, the CLIP-cells. In organoids derived from patients carrying heterozygous TSC2 mutations, dysregulation of mTOR signaling leads to CLIP-cell over-proliferation and formation of cortical tubers and subependymal tumors. Surprisingly, second-hit events resulting from copy-neutral loss-of-heterozygosity (cnLOH) are not causative for but occur during the progression of tumor lesions. Instead, EGFR signaling is required for tumor proliferation, opening up a promising approach to treat TSC lesions. Our study demonstrates that the analysis of developmental disorders in organoid models can lead to fundamental insights into human brain development and neuropsychiatric disorders.

Laser and the Tuber: Thermal Dynamic and Volumetric Factors Influencing Seizure Outcomes in Pediatric Subjects With Tuberous Sclerosis Undergoing Stereoencephalography-Directed Laser Ablation of Tubers

INTRODUCTION Tuberous Sclerosis (TSC) is a well-known cause of Medically Refractory Epilepsy (MRE). It is well documented that early surgical management can improve patient outcomes. Stereoencephalography-directed Magnetic Resonance guided Laser Interstitial Thermal Therapy (SEEG-directed MRgLITT) is an emerging minimally invasive technique that appears aptly suited for the surgical management of this condition. Our aims are to present our experiences with patients who had undergone prior SEEG-directed MRgLITT to identify and treat cortical tubers responsible for clinical seizures and to perform an in-depth analysis of volumetric and thermal dynamic factors that may be related to seizure outcomes. METHODS We studied all pediatric patients with MRE due to TSC who underwent SEEG-directed MRgLITT, investigating seizure outcomes in relationship to thermal dynamic and volumetric factors of MRgLITT when applied to cortical tubers. RESULTS About 8 cortical tubers from 3 pediatric patients were analyzed. About 2 out of 3 patients had Engel I outcomes at last follow-up. Median follow-up was 15 mo. Average A/T (ablation volume/tuber volume) ratio for Engel I outcomes was 1.28 (variance, 0.16) and 0.84 (variance < 0.01) for all other outcomes (P = .035). When assessing thermal dynamic properties of cortical tuber tissue, there was a moderate positive correlation when comparing ablation energy to ablation volume (R2 = 0.65). When the calcified tuber is excluded from regression analysis, the correlation is stronger (R2 = 0.77). Thus, the calculated volume to ablate 1 cm3 of cortical tuber tissue is 1263.6 J (calcified tuber) or 1089.5 J (noncalcified tuber). CONCLUSION SEEG-directed MRgLITT is a safe and effective technique in the management of pediatric patients with MRE due to TSC. It appears that the A/T ratio is a useful indicator in predicting seizure outcomes.