bims-tubesc Biomed News
on Molecular mechanisms in tuberous sclerosis
Issue of 2021‒03‒21
twelve papers selected by
Marti Cadena Sandoval

  1. Epileptic Disord. 2021 Feb 01. 23(1): 53-73
      Tuberous sclerosis complex (TSC) is a multisystem genetic disorder associated with refractory early-onset epilepsy. Current evidence supports surgery as the intervention most likely to achieve long-term seizure freedom, but no specific guidelines are available on TSC pre-surgical workup. This critical review assesses which TSC patients are suitable for surgical treatment, when pre-surgical evaluation should start, and what degree of surgical resection is optimal for postsurgical outcome. We searched for publications from 2000 to 2020 in Pubmed and Embase using the terms "tuberous sclerosis," "epilepsy," and "epilepsy surgery". To evaluate postsurgical seizure outcome, we selected only studies with at least one year of follow-up. Overall, we collected data on 1,026 patients from 34 studies. Age at surgery ranged from one month to 54 years. Mean age at surgery was 8.41 years. Of the diagnostic non-invasive pre-surgical tools, MRI and video-EEG were considered most appropriate. Promising data for epileptogenic tuber detection is provided from invasive SEEG studies. Data on surgery and related outcome were available for 769 patients. Seizure freedom was seen in 64.4% of patients who underwent tuberectomy, 68.9% treated with lobectomy and 65.1% with multilobar resection. The most effective surgical approach was lobectomy, even though more recently tuberectomy associated with the resection of the perituberal area seems to be the best approach to reach seizure freedom. Published postsurgical seizure freedom rates in patients with TSC were between 65% and 75%, but reduced to 48%-57% over longer follow-up periods. Early surgery might positively affect neurodevelopmental trajectory in some patients, even though data on cognitive outcome are still to be confirmed with longitudinal studies. Considering the strong correlation between epilepsy duration and neurocognitive outcome, all patients with TSC ought to be referred early to a dedicated epilepsy centre for individually tailored pre-surgical evaluation by a multi-disciplinary epilepsy surgery team.
    Keywords:  TSC; drug-resistant epilepsy; epilepsy surgery; infantile spasms; outcome
  2. Acta Neurol Belg. 2021 Mar 18.
      Tuberous sclerosis complex (TSC) is an autosomal-dominant, multi-system, neurocutaneous disorder characterized by hamartomas in multiple organs. This study aimed to evaluate the clinical and paraclinical manifestations of children with TSC. The clinical and paraclinical characteristics of 79 children with TSC were evaluated and the possible correlations between the factors were calculated. Among the studied children which composed of 41 females (51.9%) and 38 males (48.1%), skin manifestations as hypopigmented macules as well as the brain involvement as cortical tubers in all (100%) cases, seizure in 74 (93.7%), and sub-ependymal nodules in 73 (92.4%) patients were the most common findings. The renal angiomyolipoma was diagnosed in 36 (70.6%) out of 51 patients. Subependymal giant cell astrocytoma in 25 (3/54%) out of 46 patients, retinal hamartoma in 15 (42.9%) out of 35 patients, and cardiac rhabdomyoma in 17 (41.3%) out of 46 patients were diagnosed. Furthermore, 50 (63.3%) out of 79 patients had psychological disorders that had a significant correlation with the prevalence of seizures (p = 0.002). Given the multi-systemic involvement of TSC, it is necessary that all organs of the patients even without any related clinical symptom or sign be examined regularly for proper therapeutic intervention and prevent disease progression. The growth of hamartomas in the brain and kidneys can be life-threatening; therefore, these organs have more importance to be regularly followed up and examined.
    Keywords:  Children; Clinical manifestations; Paraclinical manifestations; Tuberous sclerosis complex
  3. Transl Psychiatry. 2021 Mar 15. 11(1): 165
      The mechanistic target of rapamycin (mTOR) is a ubiquitously expressed kinase that acts through two complexes, mTORC1 and mTORC2, to regulate protein homeostasis, as well as long lasting forms of synaptic and behavioral plasticity. Alteration of the mTOR pathway is classically involved in neurodegenerative disorders, and it has been linked to dysregulation of cognitive functions and affective states. However, information concerning the specific involvement of the p70 S6 kinase 1 (S6K1), a downstream target of the mTORC1 pathway, in learning and memory processes and in the regulation of affective states remains scant. To fill this gap, we exposed adult male mice lacking S6K1 to a battery of behavioral tests aimed at measuring their learning and memory capabilities by evaluating reference memory and flexibility with the Morris water maze, and associative memory using the contextual fear conditioning task. We also studied their anxiety-like and depression-like behaviors by, respectively, performing elevated plus maze, open field, light-dark emergence tests, and sucrose preference and forced swim tests. We found that deleting S6K1 leads to a robust anxious phenotype concomitant with associative learning deficits; these symptoms are associated with a reduction of adult neurogenesis and neuronal atrophy in the hippocampus. Collectively, these results provide grounds for the understanding of anxiety reports after treatments with mTOR inhibitors and will be critical for developing novel compounds targeting anxiety.
  4. J Radiol Case Rep. 2021 Feb;15(2): 1-6
      Vigabatrin therapy is commonly used in infants diagnosed with tuberous sclerosis complex, particularly in the setting of epilepsy. Utilization of vigabatrin can result in bilateral and symmetric abnormal sequence changes within the deep brain matter and brainstem on magnetic resonance imaging. These abnormalities occur predominantly in infancy, are reversible, and can be asymptomatic or result in symptomatic clinical manifestations. We present a case with classic neuroimaging findings. Familiarity with these findings can prevent unnecessary follow up tests or studies and the cost of continuing or discontinuing vigabatrin therapy should be weighed heavily against the potential manifestation of extrapyramidal symptoms.
    Keywords:  MRI; Pediatric Neuroimaging; Tuberous Sclerosis Complex; VABAM; Vigabatrin; Vigabatrin Toxicity; Vigabatrin-associated brain abnormalities
  5. Clin Cancer Res. 2021 Mar 16. pii: clincanres.4548.2020. [Epub ahead of print]
      PURPOSE: This was a multicenter, histology-agnostic, single-arm prospective phase II trial of therapeutic activity of everolimus, an oral mTORC1 inhibitor, in patients with advanced solid tumors that harbored TSC1/TSC2 or MTOR mutations.EXPERIMENTAL DESIGN: Patients with tumors with inactivating TSC1/TSC2 or activating MTOR mutations identified in any CLIA-certified laboratory were eligible. Patients were treated with everolimus 10mg once daily until disease progression or unacceptable toxicity. The primary endpoint was objective response rate (ORR). Whole-exome sequencing was performed to identify co-occurring genomic alterations.
    RESULTS: Between 11/2015 and 10/2018, 30 patients were enrolled at Dana-Farber Cancer Institute and Memorial Sloan-Kettering Cancer Center. Tumors harbored TSC1 (13/30), TSC2 (15/30), concurrent TSC1 and TSC2 (1/30) or MTOR (1/30) mutations. The most common treatment-related adverse event of any grade was mucositis (8/30, 27%); one patient had fatal pneumonitis. Partial responses were seen in two patients (7%, 95%CI: 1%-22%). Median progression-free survival (PFS) was 2.3 months (95%CI: 1.8-3.7 months) and median overall survival (OS) was 7.3 months (95%CI: 4.5-12.7 months). There was no clear association between other genomic alterations and response. Of the two patients with objective response, one had upper tract urothelial carcinoma with biallelic inactivation of TSC1 and high tumor mutation burden, the other had uterine carcinoma with biallelic TSC2 inactivating mutations and PEComa-like pathologic features.
    CONCLUSIONS: Everolimus therapy had a disappointing objective response rate (7%) in this pan-cancer, mutation-selected, basket study.
  6. Orphanet J Rare Dis. 2021 Mar 17. 16(1): 133
      BACKGROUND: Lymphangioleiomyomatosis (LAM) is a rare disease that almost exclusively affects women of reproductive age. Patients are warned of the increased risks if they become pregnant. However, information on pregnancy in patients after the diagnosis of LAM is limited.METHODS: Patients were collected from the LAM registry study at Peking Union Medical College Hospital, Beijing, China. Patients with a history of pregnancy after the diagnosis of LAM were included. Medical records were reviewed, and baseline information and data during and after pregnancy were collected in May 2018.
    RESULTS: Thirty patients with a total of 34 pregnancies after the diagnosis of LAM were included. Livebirth, spontaneous abortion and induced abortion occurred in 10, 6 and 18 pregnancies, respectively. Sirolimus treatment was common (17/34). A total of 6/10, 5/6, and 6/18 patients with livebirths, spontaneous abortions, and induced abortions respectively, had a history of sirolimus treatment. Ten pregnancies (29.4%) had LAM-associated complications during pregnancy, including the exacerbation of dyspnea in 7 patients, pneumothorax in 3 patients (2 resulting in induced abortion and 1 successful parturition), and spontaneous bleeding of renal angiomyolipomas in 2 patients (both having successful parturition). No chylothorax was found during pregnancy. There were six pregnancies in six patients (17.6%) who had a history of livebirth after sirolimus treatment for LAM (all having successful parturition and healthy infants); two of these patients reported exacerbated dyspnea after parturition compared with before pregnancy.
    CONCLUSIONS: Patients with LAM, especially those taking sirolimus before pregnancy, were at a higher risk of spontaneous abortion. Complications such as pneumothorax, bleeding of renal angiomyolipoma, and exacerbated dyspnea during pregnancy were common. In patients without spontaneous abortion, sirolimus discontinuation before or during pregnancy did not lead to increased adverse neonatal outcomes.
    Keywords:  Lymphangioleiomyomatosis; Pneumothorax; Pregnancy; Sirolimus; Tuberous sclerosis complex
  7. Am J Ophthalmol Case Rep. 2021 Jun;22 101050
      Purpose: To describe the finding of bright hyperautofluorescent streaks in the peripheral retina in tuberous sclerosis.Observations: A woman with a pathogenic TSC1 mutation and cutaneous manifestations of tuberous sclerosis underwent fundus examination and was found to have a cluster of thin, yellowish streaks in the inferior peripheral fundus of her left eye. The streaks were hyperautofluorescent in blue light and associated with irregular thickening of the photoreceptor-pigment epithelium complex on optical coherence tomography.
    Conclusions and importance: The cluster of outer retinal abnormalities in a sector of the peripheral retina in one eye of a TSC1 patient has features in common with the more centrally located and less numerous lesions called achromatic patches. The resemblance of the streak pattern with the pattern of hypoautofluorescence in X-linked retinopathies suggests that the streaks may represent a clone of cells derived from a single somatic mutation in TSC1. The identification of this lesion type expands the scope of conditions that can be diagnosed by fundus imaging.
    Keywords:  Fundus autofluorescence; Fundus photography; Optical coherence tomography; Retina; Tuberous sclerosis
  8. Commun Biol. 2021 Mar 19. 4(1): 355
      Mechanical stress induced by contractions constantly threatens the integrity of muscle Z-disc, a crucial force-bearing structure in striated muscle. The PDZ-LIM proteins have been proposed to function as adaptors in transducing mechanical signals to preserve the Z-disc structure, however the underlying mechanisms remain poorly understood. Here, we show that LDB3, a well-characterized striated muscle PDZ-LIM protein, modulates mechanical stress signaling through interactions with the mechanosensing domain in filamin C, its chaperone HSPA8, and PKCα in the Z-disc of skeletal muscle. Studies of Ldb3Ala165Val/+ mice indicate that the myopathy-associated LDB3 p.Ala165Val mutation triggers early aggregation of filamin C and its chaperones at muscle Z-disc before aggregation of the mutant protein. The mutation causes protein aggregation and eventually Z-disc myofibrillar disruption by impairing PKCα and TSC2-mTOR, two important signaling pathways regulating protein stability and disposal of damaged cytoskeletal components at a major mechanosensor hub in the Z-disc of skeletal muscle.
  9. Arch Pediatr. 2021 Mar 11. pii: S0929-693X(21)00027-0. [Epub ahead of print]
      BACKGROUND: Tuberous sclerosis (TS) is an autosomal dominant and hereditary disorder. Cardiac rhabdomyoma and arrhythmias are the most deleterious risk factors linked to TS. Although arrhythmias in pediatric patients with TS who have cardiac rhabdomyoma have been frequently reported, arrhythmia in patients who have TS without rhabdomyoma is rarely reported in the literature. The study aimed to assess the susceptibility of pediatric patients who have TS without cardiac rhabdomyoma to cardiac arrhythmia using electrocardiographic (ECG) markers.METHODS: This prospective study included 10 patients who had TS without cardiac rhabdomyoma. The control group was made up of 30 healthy children of the same age and sex as the patient group. P wave, P wave dispersion, QT dispersion, QTc dispersion, TP-e interval, and TP-e interval dispersion were calculated on 12-lead surface ECGs for each patient in both groups and compared.
    RESULTS: P wave, P wave dispersion, QT dispersion, and QTc dispersion were found to be significantly higher in the patient group (P<0.001). Furthermore, patients had a greater Tp-e interval and Tp-e interval dispersion than healthy children (P<0.001).
    CONCLUSION: Pediatric patients with TS without cardiac rhabdomyoma might be prone to atrial and ventricular arrhythmias according to their prolonged ECG markers. Our findings suggest that patients with TS without cardiac rhabdomyoma need close monitoring for atrial and ventricular arrhythmias.
    Keywords:  Cardiac rhabdomyoma; P wave dispersion; QTc dispersion; Tp-e interval dispersion; Tuberous sclerosis
  10. J Exp Pharmacol. 2021 ;13 265-290
      Epilepsies are among the most common neurological problems. The disease burden in patients with epilepsy is significantly high, and epilepsy has a huge negative impact on patients' quality of life with epilepsy and their families. Anti-seizure medications are the mainstay treatment in patients with epilepsy, and around 70% of patients will ultimately control with a combination of at least two appropriately selected anti-seizure medications. However, in one-third of patients, seizures are resistant to drugs, and other measures will be needed. The primary goal in using experimental therapeutic medication strategies in patients with epilepsy is to prevent recurrent seizures and reduce the rate of traumatic events that may occur during seizures. So far, various treatments using medications have been offered for patients with epilepsies, which have been classified according to the type of epilepsy, the effectiveness of the medications, and the adverse effects. Medications such as Levetiracetam, valproic acid, and lamotrigine are at the forefront of these patients' treatment. Epilepsy surgery, neuro-stimulation, and the ketogenic diet are the main measures in patients with medication-resistant epilepsies. In this paper, we will review the therapeutic approach using anti-seizure medications in patients with epilepsy. However, it should be noted that some of these patients still do not respond to existing treatments; therefore, the limited ability of current therapies has fueled research efforts for the development of novel treatment strategies. Thus, it seems that in addition to surgical measures, we should look for more specific agents that have less adverse events and have a greater effect in stopping seizures.
    Keywords:  drug strategies; epilepsy; experimental therapeutic; seizure
  11. Neurology. 2021 Mar 15. pii: 10.1212/WNL.0000000000011846. [Epub ahead of print]
      OBJECTIVE: To test the hypothesis that glutamate and GABA are linked to the formation of epilepsy networks and the triggering of spontaneous seizures, we examined seizure initiation/propagation characteristics and neurotransmitter levels during epileptogenesis in a translationally relevant rodent model of mesial temporal lobe epilepsy.METHODS: The glutamine synthetase (GS) inhibitor methionine sulfoximine was infused into one of the hippocampi in laboratory rats to create a seizure focus. Long-term video-intracranial EEG recordings and brain microdialysis combined with mass spectrometry were used to examine seizure initiation, seizure propagation, and extracellular brain levels of glutamate and GABA.
    RESULTS: All seizures (n = 78 seizures, n = 3 rats) appeared first in the GS-inhibited hippocampus of all animals, followed by propagation to the contralateral hippocampus. Propagation time decreased significantly from 11.65 seconds early in epileptogenesis (weeks 1-2) to 6.82 seconds late in epileptogenesis (weeks 3 - 4, paired t-test, p = 0.025). Baseline extracellular glutamate levels were 11.6-fold higher in the hippocampus of seizure propagation (7.3 µM) vs. the hippocampus of seizure onset (0.63 µM, ANOVA/Fisher's LSD, p = 0.01), even though the concentrations of the major glutamate transporter proteins EAAT1, EAAT2 and xCT were unchanged between the brain regions. Finally, extracellular GABA in the seizure focus decreased significantly from baseline several hours before a spontaneous seizure (paired t-test/FDR).
    CONCLUSION: The changes in glutamate and GABA suggest novel and potentially important roles of the amino acids in epilepsy network formation and in the initiation and propagation of spontaneous seizures.
  12. Brain Commun. 2021 ;3(1): fcaa235
      Brain somatic mutations are an increasingly recognized cause of epilepsy, brain malformations and autism spectrum disorders and may be a hidden cause of other neurodevelopmental and neurodegenerative disorders. At present, brain mosaicism can be detected only in the rare situations of autopsy or brain biopsy. Liquid biopsy using cell-free DNA derived from cerebrospinal fluid has detected somatic mutations in malignant brain tumours. Here, we asked if cerebrospinal fluid liquid biopsy can be used to detect somatic mosaicism in non-malignant brain diseases. First, we reliably quantified cerebrospinal fluid cell-free DNA in 28 patients with focal epilepsy and 28 controls using droplet digital PCR. Then, in three patients we identified somatic mutations in cerebrospinal fluid: in one patient with subcortical band heterotopia the LIS1 p. Lys64* variant at 9.4% frequency; in a second patient with focal cortical dysplasia the TSC1 p. Phe581His*6 variant at 7.8% frequency; and in a third patient with ganglioglioma the BRAF p. Val600Glu variant at 3.2% frequency. To determine if cerebrospinal fluid cell-free DNA was brain-derived, whole-genome bisulphite sequencing was performed and brain-specific DNA methylation patterns were found to be significantly enriched (P = 0.03). Our proof of principle study shows that cerebrospinal fluid liquid biopsy is valuable in investigating mosaic neurological disorders where brain tissue is unavailable.
    Keywords:  cell-free DNA; cerebrospinal fluid; focal epilepsy; liquid biopsy; somatic mutations