bims-tubesc Biomed News
on Molecular mechanisms in tuberous sclerosis
Issue of 2021‒08‒22
fourteen papers selected by
Marti Cadena Sandoval

  1. J Neurosci. 2021 Aug 20. pii: JN-RM-1930-20. [Epub ahead of print]
      Tuberous sclerosis complex (TSC) is a multisystem developmental disorder characterized by hamartomas in various organs such as the brain, lungs, and kidneys. Epilepsy, along with autism and intellectual disability, is one of the neurological impairments associated with TSC that has an intimate relationship with developmental outcomes and quality of life. Sustained activation of the mammalian target of rapamycin (mTOR) via TSC1 or TSC2 mutations is known to be involved in the onset of epilepsy in TSC. However, the mechanism by which mTOR causes seizures remain unknown. In this study, we showed that, human induced pluripotent stem cell-derived TSC2-deficient (TSC2-/- ) neurons exhibited elevated neuronal activity with highly synchronized Ca2+ spikes. Notably, TSC2-/- neurons presented enhanced Ca2+ influx via L-type Ca2+ channels (LTCCs), which contributed to the abnormal neurite extension and sustained activation of cAMP response element binding protein (CREB), a critical mediator of synaptic plasticity. Expression of Cav1.3, a subtype of LTCCs, was increased in TSC2-/- neurons, but long-term rapamycin treatment suppressed this increase and reversed the altered neuronal activity and neurite extensions. Thus, we identified Cav1.3 LTCC as a critical downstream component of TSC-mTOR signaling that would trigger enhanced neuronal network activity of TSC2-/- neurons. We suggest that LTCCs could be potential novel targets for the treatment of epilepsy in TSC.Significant statementThere is a close relationship between elevated mTOR activity and epilepsy in tuberous sclerosis complex (TSC). However, the underlying mechanism by which mTOR causes epilepsy remains unknown. In this study, using human TSC2-/- neurons, we identified elevated Ca2+ influx via LTCCs as a critical downstream component of TSC-mTOR signaling and a potential cause of both elevated neuronal activity and neurite extension in TSC2-/- neurons. Our findings demonstrate a previously unrecognized connection between sustained mTOR activation and elevated Ca2+ signaling via LTCC in human TSC neurons, which could cause epilepsy in TSC.
  2. CNS Drugs. 2021 Aug 21.
      Epilepsy is one of the main symptoms affecting the lives of individuals with tuberous sclerosis complex (TSC), causing a high rate of morbidity. Individuals with TSC can present with various types of seizures, epilepsies, and epilepsy syndromes that can coexist or appear in relation to age. Focal epilepsy is the most frequent epilepsy type with two developmental and epileptic encephalopathies: infantile spasms syndrome and Lennox-Gastaut syndrome. Active screening and early management of epilepsy is recommended in individuals with TSC to limit its consequences and its impact on quality of life, cognitive outcome and the economic burden of the disease. The progress in the knowledge of the mechanisms underlying epilepsy in TSC has paved the way for new concepts in the management of epilepsy related to TSC. In addition, we are moving from traditional "reactive" and therapeutic choices with current antiseizure medications used after the onset of seizures, to a proactive approach, aimed at predicting and preventing epileptogenesis and the onset of epilepsy with vigabatrin, and to personalized treatments with mechanistic therapies, namely mechanistic/mammalian target of rapamycin inhibitors. Indeed, epilepsy linked to TSC is one of the only epilepsies for which a predictive and preventive approach can delay seizure onset and improve seizure response. However, the efficacy of such interventions on long-term cognitive and psychiatric outcomes is still under investigation.
  3. Pediatr Neurol. 2021 Jul 23. pii: S0887-8994(21)00149-1. [Epub ahead of print]123 38-39
    Keywords:  Mosaic; SEGA; TSC; mTOR
  4. Front Cell Dev Biol. 2021 ;9 710407
      Adenomyosis (AM) is a disease in which endometrial tissue invades the myometrium and has a 10-60% prevalence in reproductive-aged women. TSC2 regulates autophagy via mTOR1 signalling in colorectal cancer and endometrial carcinoma. Dysregulation of autophagy is implicated in adenomyosis pathogenesis. However, whether TSC2 participates in adenomyosis via autophagy remains obscure. Here, we found that the expression of TSC2 in adenomyosis was significantly decreased than that in normal endometrium during the secretory phase. Moreover, TSC2 and autophagy marker expression was significantly lower in ectopic lesions than in eutopic samples. TSC2 downregulation inhibited autophagy through mTOR1 signalling pathway activation in endometrial cells, leading to excessive proliferation, migration, and EMT; TSC2 overexpression induced the opposite effects. Rapamycin treatment suppressed cell proliferation, migration and EMT in the absence of TSC2. In parallel, an autophagy-specific inhibitor (SAR-405) restored migration and EMT under rapamycin treatment in TSC2-knockdown Ishikawa cells. Finally, SAR-405 treatment promoted EMT and migration of overexpressing cells. Collectively, our results suggest that TSC2 controls endometrial epithelial cell migration and EMT by regulating mTOR1-autophagy axis activation and that hypo-expression of TSC2 in the endometrium might promote adenomyosis.
    Keywords:  EMT; TSC2; adenomyosis; autophagy; endometrial cell; mTOR1; migration
  5. Eur J Med Genet. 2021 Aug 14. pii: S1769-7212(21)00175-0. [Epub ahead of print]64(10): 104309
      The aim of this study was to evaluate a cost-effective diagnostic strategy for identification of casual variants for tuberous sclerosis complex (TSC) in the Polish population and to correlate the genetic results with selected phenotypic features. Fifty-five patients, aged 3-44 years, with a clinical diagnosis of TSC were enrolled into the study. All patients received a three-step analysis: next generation sequencing screening (NGS), multiplex ligation-dependent probe amplification (MLPA) and deep sequencing. This multistep approach obtained positive results in 51/55 (93%) patients: of the 51 positives TSC1 variants were observed in 16 (31%) and TSC2 variants in 35 (69%); these included 13 novel variants and two patients with mosaicism. Four patients (7%) had no mutation identified (NMI). Among the TSC1 gene variants, there were five nonsense, four frameshift, three large deletions, two missense and two splicing variants. For the TSC2 gene, 11 were missense, eight splicing, six frameshift, four large deletions, two in-frame deletions and four nonsense variants. The patients with TSC2 changes had their clinical diagnosis of TSC at a younger age than those with TSC1 changes (one year vs three years, p = 0.041). The TSC2 group demonstrated a higher number of major symptoms per patient (p = 0.04). Subependymal giant cell astrocytoma with concomitance of other brain lesions was more common in patients with missense mutations in either gene (23% vs 0%, p = 0.02). Such a multistep molecular diagnostic strategy could increase the possibility of detecting causal variants for TSC and may allow detection of mosaicism at low levels. Missense pathogenic variants in TSC1 or TSC2 gene might be associated with a higher risk of brain lesions.
    Keywords:  Genotype-phenotype correlation; Mosaicism; NGS; Novel pathogenic variants; Tuberous sclerosis complex
  6. Pediatr Neurol. 2021 Jun 26. pii: S0887-8994(21)00138-7. [Epub ahead of print]123 43-49
      BACKGROUND: The neurodevelopmental impairment in tuberous sclerosis complex (TSC) has a multifactorial origin. Various factors have been proposed as predictors of neurological outcome such as tuber load, seizure onset, and TSC2 mutation. Cerebellar lesions have been associated with worse neuroradiological phenotype, but their contribution is not well understood.METHODS: A partly retrospective and partly prospective pediatric cohort study was conducted at three hospitals in Greece between 2015 and 2020. Patients aged ≤ 18 years with a confirmed TSC daignosis were included and underwent brain imaging, a semistructured interview (authorized Greek version of the tuberous sclerosis-associated neuropsychiatric disorders, or TAND, checklist), and intellectual ability assessment.
    RESULTS: The study populations consisted of 45 patients with TSC (22 females, 23 males; mean age 9.53 years). Twenty patients (44.4%) had cerebellar lesions. Cerebellar involvement was the most powerful predictor of tuber load (P = 0.03). Cerebellar lesions were associated with giant cell astrocytomas (SEGAs) (P = 0.01) and severe neurological outcome (P = 0.01). Even though in the univariate analysis early seizure onset, tuber load, and cerebellar involvement were associated with intellectual impairment and neurological severity, none of them was an independent predictor of cognitive outcome and neurological severity.
    CONCLUSIONS: Cerebellar lesions are common among individuals with TSC. Cerebellar involvement correlates with supratentorial derangement and the development of SEGAs, which is suggestive of a more severe clinical and neuroradiological phenotype. Cerebellar involvement and early seizure onset were not independent predictors of either neurological severity or intellectual disability or neurobehavioral outcome; their role in TSC clinical phenotype should be further investigated.
    Keywords:  Cerebellar lesions; Cortical tubers; Epilepsy; Intellectual disability; Neurological outcome; Tuberous sclerosis complex
  7. Pediatr Neurol. 2021 Jul 26. pii: S0887-8994(21)00152-1. [Epub ahead of print]123 77-84
      BACKGROUND: Tuberous Sclerosis Complex International (TSCi) is a consortium of organizations that supports individuals with tuberous sclerosis complex (TSC) around the world. To improve care for TSC on a global level, TSCi identified the need to expand understanding about existing resources available in other countries, what individuals and caregivers value in TSC care, key gaps between needs and reality in each country, and ways these gaps can be addressed by advocacy organizations around the world.METHODS: An iterative, mixed methods approach (the Improving Care project) was adopted to incorporate views from diverse members of TSCi. Through idea generation, a collection of qualitative open-ended responses and concept elicitation, we were able to build consensus where shared experiences and opinions were identified.
    RESULTS: The research performed as a part of the Improving Care project revealed a significant gap between the guidelines and what is actually available to people with TSC worldwide. Three key priority areas of action to improve this gap were identified: (1) implementation of the guidelines; (2) access to TSC expertise, and (3) coordinated and integrated health care.
    CONCLUSIONS: There are significant opportunities for key stakeholders, including organizations, clinicians, and researchers to improve care for individuals with TSC on both local and global levels. Working across stakeholder groups and utilizing TSC organizations are essential to ensure that the advances in TSC research benefit people living with TSC around the world.
    Keywords:  Access to care; Advocacy organization; Care coordination; Halth care delivery; Rare disease; TSC1; TSC2; Tuberous sclerosis complex
  8. Dermatol Pract Concept. 2021 Jul;11(3): e2021036
    Keywords:  Facial angiofibroma; angiofibroma; dermoscopy; tuberous sclerosis complex
  9. J Vis Exp. 2021 Aug 02.
      Macropinocytosis is a highly conserved, actin-dependent endocytic process that allows the uptake of extracellular material, including proteins and lipids. In proliferating cells, macropinocytosis can deliver extracellular nutrients to the lysosome, processed into critical macromolecule building blocks. Recent studies have highlighted the dependence of multiple cancers on macropinocytosis, including breast, colorectal and pancreatic cancer. Ras mutations are thought to be the driver events behind macropinocytosis initiation, leading to the activation of cellular anabolic processes via the mTORC1 signaling pathway. Interestingly, mTORC1 can also be activated by macropinocytosis independently of Ras. Therefore, macropinocytosis represents a metabolic vulnerability that can be leveraged to target macropinocytic tumors by limiting their access to nutrients therapeutically. In Tuberous Sclerosis Complex (TSC) and Lymphangioleiomyomatosis (LAM), mTORC1-hyperactivation leads to enhanced macropinocytosis and metabolic reprogramming. Here, we describe a flow cytometry-based protocol to assess macropinocytosis in mammalian cells quantitatively. TSC2-deficient MEFs are employed, which exhibit aberrant activation of mTORC1 and have been shown to have increased macropinocytosis compared to TSC2-expressing cells. Cells treated with pharmacologic inhibitors of macropinocytosis are incubated with fluorescently labeled, lysine-fixable, 70 kDa dextran, or fluorescently labeled bovine serum albumin (BSA) assayed by flow cytometry. To date, robust image-based techniques have been developed to quantitatively assess macropinocytosis in tumor cells in vitro and in vivo. This analysis provides a quantitative assessment of macropinocytosis in multiple experimental conditions and complements existing image-based techniques.
  10. Pediatr Neurol. 2021 Jul 24. pii: S0887-8994(21)00151-X. [Epub ahead of print]123 50-66
      BACKGROUND: Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disease affecting multiple body systems with wide variability in presentation. In 2013, Pediatric Neurology published articles outlining updated diagnostic criteria and recommendations for surveillance and management of disease manifestations. Advances in knowledge and approvals of new therapies necessitated a revision of those criteria and recommendations.METHODS: Chairs and working group cochairs from the 2012 International TSC Consensus Group were invited to meet face-to-face over two days at the 2018 World TSC Conference on July 25 and 26 in Dallas, TX, USA. Before the meeting, working group cochairs worked with group members via e-mail and telephone to (1) review TSC literature since the 2013 publication, (2) confirm or amend prior recommendations, and (3) provide new recommendations as required.
    RESULTS: Only two changes were made to clinical diagnostic criteria reported in 2013: "multiple cortical tubers and/or radial migration lines" replaced the more general term "cortical dysplasias," and sclerotic bone lesions were reinstated as a minor criterion. Genetic diagnostic criteria were reaffirmed, including highlighting recent findings that some individuals with TSC are genetically mosaic for variants in TSC1 or TSC2. Changes to surveillance and management criteria largely reflected increased emphasis on early screening for electroencephalographic abnormalities, enhanced surveillance and management of TSC-associated neuropsychiatric disorders, and new medication approvals.
    CONCLUSIONS: Updated TSC diagnostic criteria and surveillance and management recommendations presented here should provide an improved framework for optimal care of those living with TSC and their families.
    Keywords:  Diagnostic criteria; Practical guidance; Surveillance and management guidelines; Tuberous sclerosis complex (TSC)
  11. Front Cell Neurosci. 2021 ;15 668500
      Impaired energy homeostasis and aberrant translational control have independently been implicated in the pathogenesis of neurodegenerative diseases. AMP kinase (AMPK), regulated by the ratio of cellular AMP and ATP, is a major gatekeeper for cellular energy homeostasis. Abnormal regulation of AMPK has been reported in several neurodegenerative diseases, including Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS). Most importantly, AMPK activation is known to suppress the translational machinery by inhibiting the mechanistic target of rapamycin complex 1 (mTORC1), activating translational regulators, and phosphorylating nuclear transporter factors. In this review, we describe recent findings on the emerging role of protein translation impairment caused by energy dysregulation in neurodegenerative diseases.
    Keywords:  AMP kinase; Alzheimer’s disease; amyotrophic lateral sclerosis; protein translation; stress granules
  12. J Pediatr. 2021 Aug 11. pii: S0022-3476(21)00765-4. [Epub ahead of print]
      OBJECTIVE: To evaluate whether children with neurofibromatosis type 1 (NF1) and tuberous sclerosis have different birth characteristics compared with the general population.STUDY DESIGN: We identified all individuals born in Sweden between 1973 and 2014 from the nationwide Medical Birth Register, for whom information on both biological parents was available (n=4 242 122). NF1 and TS patients were identified using data from Swedish population-based health data registers. We assessed using logistic regression models the association between these neurocutaneous syndromes and birth characteristics in a cohort that included 1804 NF1 and 450 TS patients.
    RESULTS: Children with NF1 and TS were significantly more likely to be born preterm and via a caesarean section. In addition, children with NF1 were also more likely to be born with other birth characteristics, such as short length, a large head circumference, and a low Apgar score. Moreover, children with NF1 had an increased odds of being born with a high birth weight or large for gestational age (OR 1.61, 95% CI 1.42-1.82 and OR 1.82, 95% CI 1.60-2.06, respectively).
    CONCLUSION: Children with NF1 1 and TS differ from the general population in regard to several birth characteristics, with the strongest associations observed for high birth weight and being large for gestational age in individuals with NF1.
  13. Int J Surg Pathol. 2021 Aug 17. 10668969211038737
      Eosinophilic solid and cystic renal cell carcinoma (ESC-RCC) is an emerging entity in renal neoplasia with distinctive histopathological findings and a generally favorable prognosis. The presence of melanin pigment in a renal tumor typically prompts the observer to consider the microphthalmia-associated transcription family translocation renal cell carcinomas. We present a renal tumor occurring in a 19-year-old male patient which had the typical morphology of ESC-RCC but showed the additional finding of focal melanin pigment. This tumor showed strong and diffuse positive immunolabeling with paired box gene 8 and cytokeratin 20, and was negative with epithelial membrane antigen, carbonic anhydrase 9, CD117, cytokeratin 7, and transcription factor E3. Human melanoma black-45 showed focal positivity, but Melan-A was negative. Next-generation sequencing revealed a mutation in the TSC2 gene (c.4490C > G, p.[Pro1497Arg] and c.1257 + 1del) and break apart fluorescence in-situ hybridization with TFE3 and TFEB probes was negative. In this case report, we present the novel finding of melanin pigment occurring in a genetically proven and otherwise typical ESC-RCC, and briefly discuss the differential diagnostic considerations.
    Keywords:  TFE3; TSC; genitourinary pathology; immunohistochemistry; kidney tumor; melanin pigment; renal cell carcinoma