bims-tubesc Biomed News
on Molecular mechanisms in tuberous sclerosis
Issue of 2021‒02‒28
ten papers selected by
Marti Cadena Sandoval

  1. J Genet Genomics. 2021 Jan 13. pii: S1673-8527(21)00001-1. [Epub ahead of print]
      Tuberous sclerosis complex (TSC) is a dominant genetic neurocutaneous syndrome characterized by multiple organ hamartomas. Although rodent models bearing a germline mutation in either TSC1 or TSC2 genes have been generated, they do not develop pathogenic lesions matching those seen in patients with TSC because of the significant differences between mice and humans, highlighting the need for an improved large animal model of TSC. Here, we successfully generated monoallelic TSC1-modified Bama miniature pigs using the CRISPR/Cas9 system along with somatic cell nuclear transfer (SCNT) technology. The expression of phosphorylated target ribosomal protein S6 was significantly enhanced in the piglets, indicating that disruption of a TSC1 allele activated the mechanistic target of rapamycin (mTOR) signaling pathway. Notably, differing from the mouse TSC models reported previously, the TSC1+/- Bama miniature pig developed cardiac rhabdomyoma and subependymal nodules, resembling the major clinical features that occur in patients with TSC. These TSC1+/- Bama miniature pigs could serve as valuable large animal models for further elucidation of the pathogenesis of TSC and the development of therapeutic strategies for TSC disease.
    Keywords:  CRISPR/Cas9; Cardiac rhabdomyosarcoma; Subependymal nodules; TSC1; Tuberous sclerosis complex
  2. Front Cell Dev Biol. 2020 ;8 616747
      Renal fibrosis is considered as the final pathway of all types of kidney diseases, which can lead to the progressive loss of kidney functions and eventually renal failure. The mechanisms behind are diversified, in which the mammalian target of rapamycin (mTOR) pathway is one of the most important regulatory pathways that accounts for the disease. Several processes that are regulated by the mTOR pathway, such as autophagy, epithelial-mesenchymal transition (EMT), and endoplasmic reticulum (ER) stress, are tightly associated with renal fibrosis. In this study, we have reported that the expression of tripartite motif-containing (TRIM) protein 6, a member of TRIM family protein, was highly expressed in renal fibrosis patients and positively correlated with the severity of renal fibrosis. In our established in vitro and in vivo renal fibrosis models, its expression was upregulated by the Angiotensin II-induced nuclear translocation of nuclear factor-κB (NF-κB) p50 and p65. In HK2 cells, the expression of TRIM6 promoted the ubiquitination of tuberous sclerosis proteins (TSC) 1 and 2, two negative regulators of the mTORC1 pathway. Moreover, the knockdown of TRIM6 was found efficient for alleviating renal fibrosis and inhibiting the downstream processes of EMT and ER in both HK2 cells and 5/6-nephrectomized rats. Clinically, the level of TRIM6, TSC1/2, and NF-κB p50 was found closely related to renal fibrosis. As a result, we have presented the first study on the role of TRIM6 in the mTORC1 pathway in renal fibrosis models and our findings suggested that TRIM6 may be a potential target for the treatment of renal fibrosis.
    Keywords:  TRIM6; TSC1; TSC2; angiotensin II; mTOR; renal fibrosis
  3. Actas Urol Esp. 2021 Feb 23. pii: S0210-4806(20)30258-8. [Epub ahead of print]
      INTRODUCTION: Renal angiomyolipoma is a frequent manifestation of Tuberous Sclerosis Complex (TSC), for which everolimus therapy has been recently established as a novel non-invasive therapeutic option. As there are limited real life and long-term data, the analysis of our experience provides added value in terms of safety and efficacy.MATERIAL AND METHODS: Descriptive analysis of our experience in patients with giant bilateral renal angiomyolipomas, in the context of TSC, treated with 10 mg oral everolimus daily, during a median of 71.5 months. We evaluated the following parameters: response rate and duration, reduction of kidney size and lesions, prevention of complications and presentation of toxicity and its cause.
    RESULTS: We confirm the effectiveness of treatment in 4 young patients, with multiple, bilateral angiomyolipomas of a median of 12 (5-19) cm maximum diameter, from June 2013 to date, after continuous reduction in lesion size, a decrease of 30% of the volume in 75% at six months and 50% in half of the subjects at two years, still showing drug response. Absence of complications such as bleeding or glomerular filtration rate decline in the long term, with a favorable safety profile, without interruptions and with mild-moderate, non-cumulative adverse effects, mostly within the first year of treatment.
    CONCLUSION: Everolimus is a safe and effective therapeutic option for renal angiomyolipoma and various manifestations of TSC, which has been reproduced in real life with six years of follow-up.
    Keywords:  Angiomiolipoma; Angiomyolipoma; Complejo esclerosis tuberosa; Everolimus; Safety; Seguridad; Tuberous Sclerosis Complex
  4. Pharmgenomics Pers Med. 2021 ;14 269-278
      Purpose: To explore the value of Tuberous sclerosis complex 2 (TSC2) mutations in evaluating the early recurrence of hepatocellular carcinoma (HCC) patients underwent hepatectomy.Patients and Methods: A total of 183 HCC patients were enrolled. Next-generation sequencing was performed on tumor tissues to analyze genomic alterations, tumor mutational burden and variant allele fraction (VAF). The associations between TSC2 mutations and recurrence rate within 1 year, RFS and OS after hepatectomy were analyzed.
    Results: Our results showed that TSC2 mutation frequency in HCC was 12.6%. Compared to patients without TSC2 mutation, the proportion of microvascular invasion (MVI) and Edmondson grade III-IV was significantly higher in patients with a TSC2 mutation (p<0.05). The VAF of mutated TSC2 was higher in patients with maximum diameter of tumor >5cm or MVI than that of other patients (p<0.05). The frequency of TP53 mutation was significantly higher in patients with a TSC2 mutation than those without TSC2 mutation (p=0.003). Follow-up analysis showed that patients with a TSC2 mutation had significantly higher recurrence rate within 1 year (p=0.015) and poorer median recurrence-free survival (RFS) (p=0.010) than patients without TSC2 mutation. TSC2 mutations did not significantly affect overall survival of patients (p=0.480). The multivariate analysis results showed that the Barcelona Clinic Liver Cancer (BCLC) B-C stage, TSC2 mutations and preoperative serum alpha-fetoprotein level ≥400μg/L were independently associated with recurrence within 1 year after hepatectomy (HR=8.628, 95% CI: 3.836-19.405, p=0.000; HR=3.885, 95% CI: 1.295-11.653, p=0.015; HR=2.327, 95% CI: 1.018-5.323, p=0.045; respectively), and poorer RFS after hepatectomy (HR=3.070, 95% CI: 1.971-4.783, p=0.000; HR=1.861, 95% CI: 1.061-3.267, p=0.030; HR=1.715, 95% CI: 1.093-2.693, p=0.019; respectively).
    Conclusion: TSC2 mutations were significantly associated with MVI in liver para-carcinoma tissue and Edmondson grade III-IV in patients with HCC and were independently associated with recurrence within 1 year and poorer RFS after hepatectomy. The TSC2 mutation may be a potential predictor for early recurrence in HCC patients underwent hepatectomy.
    Keywords:  early recurrence; gene mutation; hepatocellular carcinoma; next-generation sequencing; tuberous sclerosis complex 2
  5. Epilepsia. 2021 Feb 27.
      Developmental and epileptic encephalopathies (DEEs) are among the most challenging of all epilepsies to manage, given the exceedingly frequent and often severe seizure types, pharmacoresistance to conventional antiseizure medications, and numerous comorbidities. During the past decade, efforts have focused on development of new treatment options for DEEs, with several recently approved in the United States or Europe, including cannabidiol as an orphan drug in Dravet and Lennox-Gastaut syndromes and everolimus as a possible antiepileptogenic and precision drug for tuberous sclerosis complex, with its impact on the mammalian target of rapamycin pathway. Furthermore, fenfluramine, an old drug, was repurposed as a novel therapy in the treatment of Dravet syndrome. The evolution of new insights into pathophysiological processes of various DEEs provides possibilities to investigate novel and repurposed drugs and to place them into the context of their role in future management of these patients. The purpose of this review is to provide an overview of these new medical treatment options for the DEEs and to discuss the clinical implications of these results for improved treatment.
    Keywords:  Dravet syndrome; Lennox-Gastaut syndrome; antiseizure medications; cannabidiol; drug repurposing; everolimus; fenfluramine; orphan drugs; tuberous sclerosis
  6. Saudi Med J. 2021 Mar;42(3): 332-337
      Pancreatic neuroendocrine tumors are rare with an incident rate of 5 cases per million individuals. Tuberous sclerosis complex is an autosomal dominant disease. This disease involves multisystem and occurs in one out of every 6,000-10,000 individuals. In this study, we describe a 47-year-old male known tuberous sclerosis patient with an insulinoma. The tumor was incidentally detected in follow-up imaging for a previous ampulla of Vater tubular adenoma. However, the patient reported symptoms of hypoglycemia. The insulinoma was enucleated successfully. Histopathology revealed a well-differentiated, grade one neuroendocrine tumor measuring around 2 cm in diameter. Seven cases were reported in the literature of tuberous sclerosis-associated insulinoma. The 7 reported cases had different hypoglycemia related symptoms. The reported tumors varied in size and location on the pancreas. This paper details the eighth case worldwide where an insulinoma occurred in a tuberous sclerosis patient.
    Keywords:  case reports; insulinoma; neuroendocrine tumors; review; tuberous sclerosis
  7. J Pediatr. 2021 Feb 22. pii: S0022-3476(21)00179-7. [Epub ahead of print]
      OBJECTIVES: To investigate the efficacy and safety of sirolimus in the treatment of cardiac rhabdomyomas ) associated with tuberous sclerosis complex (TSC) and the specific benefits in different subgroups.STUDY DESIGN: The study was a prospective cohort and self-controlled case series (SCCS) study. Based on the prevalence of CR at different ages, we estimated the natural tumor disappearance rate (TDR). The subgroup analysis was done by Cox regression. SCCS method was used to assess the magnitude and duration of the drug effect. Adverse events were described.
    RESULTS: A total of 217 patients were included in the cohort study. TDR was higher in younger age groups (HD = 0.99, P = 0.027) and female patients (HD = 2.08, P = 0.015). The age-adjusted incidence ratio showed that the disappearance of rhabdomyomas between 3 and 6 months was more related to sirolimus. Adverse events were observed 60 times in 42 of 217 children, mainly stomatitis.
    CONCLUSION: Sirolimus can increase the disappearance rate of CR in the TSC population. Efficacy varies by sex and age: female and younger patients have higher TDR. Sirolimus is well-tolerated.
    Keywords:  Cardiac tumor; Children; Rhabdomyoma; Sirolimus; Tuberous sclerosis
  8. Dev Neurobiol. 2021 Feb 22.
      Genetic diseases involving overactivation of the mechanistic target of rapamycin (mTOR) pathway, so-called "mTORopathies," often manifest with malformations of cortical development (MCDs), epilepsy, and cognitive impairment. How mTOR pathway hyperactivation results in abnormal human cortical development is poorly understood. To study the effect of mTOR hyperactivity on early stages of cortical development, we focused on Pretzel Syndrome (polyhydramnios, megalencephaly, symptomatic epilepsy; PMSE syndrome), a rare mTORopathy caused by homozygous germline mutations in the STRADA gene. We developed a human cortical organoid (hCO) model of PMSE and examined morphology and size for the first 2 weeks of organoid growth, and cell type composition at weeks 2, 8, and 12 of differentiation. In the second week, PMSE hCOs enlarged more rapidly than controls and displayed an abnormal Wnt pathway-dependent increase in neural rosette structures. PMSE hCOs also exhibited delayed neurogenesis, decreased subventricular zone progenitors, increased proliferation and cell death, and an abnormal architecture of primary cilia. At week 8, PMSE hCOs had fewer deep layer neurons. By week 12, neurogenesis recovered in PMSE organoids, but they displayed increased outer radial glia, a cell type thought to contribute to expansion of the human cerebral cortex. Together, these findings suggest that megalencephaly in PMSE arises from expansion of neural stem cells in early corticogenesis and potentially also from increased outer radial glial at later gestational stages. The delayed neuronal differentiation in PMSE organoids demonstrates the important role the mTOR pathway plays in maintenance and expansion of the stem cell pool.
    Keywords:  Pretzel Syndrome; STRADA; and symptomatic epilepsy; cerebral organoids; corticogenesis; induced pluripotent stem cells; mTOR; mechanistic target of rapamycin; megalencephaly; neurogenesis; polyhydramnios; stem cell model
  9. J Cell Biol. 2021 May 03. pii: e202004010. [Epub ahead of print]220(5):
      The mammalian target of rapamycin complex 1 (mTORC1) integrates mitogenic and stress signals to control growth and metabolism. Activation of mTORC1 by amino acids and growth factors involves recruitment of the complex to the lysosomal membrane and is further supported by lysosome distribution to the cell periphery. Here, we show that translocation of lysosomes toward the cell periphery brings mTORC1 into proximity with focal adhesions (FAs). We demonstrate that FAs constitute discrete plasma membrane hubs mediating growth factor signaling and amino acid input into the cell. FAs, as well as the translocation of lysosome-bound mTORC1 to their vicinity, contribute to both peripheral and intracellular mTORC1 activity. Conversely, lysosomal distribution to the cell periphery is dispensable for the activation of mTORC1 constitutively targeted to FAs. This study advances our understanding of spatial mTORC1 regulation by demonstrating that the localization of mTORC1 to FAs is both necessary and sufficient for its activation by growth-promoting stimuli.
  10. Inhal Toxicol. 2021 Feb 25. 1-14
      Lysosomes offer a unique arrangement of degradative, exocytic, and signaling capabilities that make their continued function critical to cellular homeostasis. Lysosomes owe their function to the activity of lysosomal ion channels and transporters, which maintain concentration gradients of H+, K+, Ca2+, Na+, and Cl- across the lysosomal membrane. This review examines the contributions of lysosomal ion channels to lysosome function, showing how ion channel function is integral to degradation and autophagy, maintaining lysosomal membrane potential, controlling Ca2+ signaling, and facilitating exocytosis. Evidence of lysosome dysfunction in a variety of disease pathologies creates a need to understand how lysosomal ion channels contribute to lysosome dysfunction. For example, the loss of function of the TRPML1 Ca2+ lysosome channel in multiple lysosome storage diseases leads to lysosome dysfunction and disease pathogenesis while neurodegenerative diseases are marked by lysosome dysfunction caused by changes in ion channel activity through the TRPML1, TPC, and TMEM175 ion channels. Autoimmune disease is marked by dysregulated autophagy, which is dependent on the function of multiple lysosomal ion channels. Understanding the role of lysosomal ion channel activity in lysosome membrane permeability and NLRP3 inflammasome activation could provide valuable mechanistic insight into NLRP3 inflammasome-mediated diseases. Finally, this review seeks to show that understanding the role of lysosomal ion channels in lysosome dysfunction could give mechanistic insight into the efficacy of certain drug classes, specifically those that target the lysosome, such as cationic amphiphilic drugs.
    Keywords:  BK; Lysosome; NLRP3; TMEM175; TRPML1; autophagy; crystalline silica; lysosomal membrane permeability