bims-tubesc 2022-01-16 papers

bims-tubesc

Biomed News

on Molecular mechanisms in tuberous sclerosis

Issue of 2022–01–16
twelve papers selected by

Abnormal activation of yap/Taz contributes to the pathogenesis of tuberous sclerosis complex.
Down-regulation of the brain-specific cell-adhesion molecule contactin-3 in tuberous sclerosis complex during the early postnatal period.
Tsc2 mutation induces renal tubular cell nonautonomous disease.
Hemispherectomy for hemimegalencephaly in a 6.5-week-old infant with tuberous sclerosis complex.
Optimization and high-density array of stereoelectroencephalography-guided radiofrequency thermocoagulation for the treatment of pediatric tuberous sclerosis complex with epilepsy.
PP2A-dependent TFEB activation is blocked by PIKfyve-induced mTORC1 activity.
Efficacy of the Ketogenic Diet for Pediatric Epilepsy According to the Presence of Detectable Somatic mTOR Pathway Mutations in the Brain.
Targeting mTOR Signaling in Type 2 Diabetes Mellitus and Diabetes Complications.
Neurodevelopmental Findings and Epilepsy in Malformations of Cortical Development.
GATOR2 complex-mediated amino acid signaling regulates brain myelination.
Thermal stress affects proliferation and differentiation of turkey satellite cells through the mTOR/S6K pathway in a growth-dependent manner.
Biomarkers of everolimus efficacy in breast cancer therapy.

Hum Mol Genet. 2022 Jan 06. pii: ddab374. [Epub ahead of print]

Abnormal activation of yap/Taz contributes to the pathogenesis of tuberous sclerosis complex.

Bethany K Terry, Raehee Park, Seo-Hee Cho, Peter B Crino, Seonhee Kim.

The multi-systemic genetic disorder tuberous sclerosis complex (TSC) impacts multiple neurodevelopmental processes including neuronal morphogenesis, neuronal migration, myelination, and gliogenesis. These alterations contribute to the development of cerebral cortex abnormalities and malformations. Although TSC is caused by mTORC1 hyperactivation, cognitive and behavioral impairments are not improved through mTORC1 targeting, making the study of the downstream effectors of this complex important for understanding the mechanisms underlying TSC. As mTORC1 has been shown to promote the activity of the transcriptional co-activator Yap, we hypothesized that altered Yap/Taz signaling contributes to the pathogenesis of TSC. We first observed that the level of Yap/Taz are increased in a human cortical tuber sample and in embryonic cortices of Tsc2 conditional knockout (cKO) mice. Next, to determine how abnormal upregulation of Yap/Taz impacts the neuropathology of TSC, we deleted Yap/Taz in Tsc2 cKO mice. Importantly, Yap/Taz/Tsc2 tcKO animals show reduced cortical thickness and cortical neuron cell size, despite the persistence of high mTORC1 activity, suggesting that Yap/Taz play a downstream role in cytomegaly. Furthermore, Yap/Taz/Tsc2 tcKO significantly restored cortical and hippocampal lamination defects and reduced hippocampal heterotopia formation. Finally, the loss of Yap/Taz increased the distribution of myelin basic protein in Tsc2 cKO animals, consistent with an improvement in myelination. Overall, our results indicate that targeting Yap/Taz lessens the severity of neuropathology in a TSC animal model. This study is the first to implicate Yap/Taz as contributors to cortical pathogenesis in TSC and therefore as potential novel targets in the treatment of this disorder.

DOI: https://doi.org/10.1093/hmg/ddab374
J Neurodev Disord. 2022 Jan 15. 14(1): 8

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

Anatoly Korotkov, Mark J Luinenburg, Alessia Romagnolo, Till S Zimmer, Jackelien van Scheppingen, Anika Bongaarts, Diede W M Broekaart, Jasper J Anink, Caroline Mijnsbergen, Floor E Jansen, Wim van Hecke, Wim G Spliet, Peter C van Rijen, Martha Feucht, Johannes A Hainfellner, Pavel Krsek, Josef Zamecnik, Peter B Crino, Katarzyna Kotulska, Lieven Lagae, Anna C Jansen, David J Kwiatkowski, Sergiusz Jozwiak, Paolo Curatolo, Angelika Mühlebner, Erwin A van Vliet, James D Mills, Eleonora Aronica.

   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.

Keywords:  Cell adhesion; Cerebral cortex development; Epilepsy; Neurodevelopmental disorders; mTORopathies

DOI:  https://doi.org/10.1186/s11689-022-09416-2
Genes Dis. 2022 Jan;9(1): 187-200

Tsc2 mutation induces renal tubular cell nonautonomous disease.

Prashant Kumar, Fahad Zadjali, Ying Yao, Daniel Johnson, Brian Siroky, Aristotelis Astrinidis, Peter Vogel, Kenneth W Gross, John J Bissler.

  TSC renal cystic disease is poorly understood and has no approved treatment. In a new principal cell-targeted murine model of Tsc cystic disease, the renal cystic epithelium is mostly composed of type A intercalated cells with an intact Tsc2 gene confirmed by sequencing, although these cells exhibit a Tsc-mutant disease phenotype. We used a newly derived targeted murine model in lineage tracing and extracellular vesicle (EV) characterization experiments and a cell culture model in EV characterization and cellular induction experiments to understand TSC cystogenesis. Using lineage tracing experiments, we found principal cells undergo clonal expansion but contribute very few cells to the cyst. We determined that cystic kidneys contain more interstitial EVs than noncystic kidneys, excrete fewer EVs in urine, and contain EVs in cyst fluid. Moreover, the loss of Tsc2 gene in EV-producing cells greatly changes the effect of EVs on renal tubular epithelium, such that the epithelium develops increased secretory and proliferative pathway activity. We demonstate that the mTORC1 pathway activity is independent form the EV production, and that the EV effects for a single cell line can vary significantly. TSC cystogenesis involves significant contribution from genetically intact cells conscripted to the mutant phenotype by mutant cell derived EVs.

Keywords:  Cell nonautonomous trait; Polycystic kidney disease; Renalcystogenesis; Tuberous sclerosis complex

DOI:  https://doi.org/10.1016/j.gendis.2021.03.010
Childs Nerv Syst. 2022 Jan 13.

Hemispherectomy for hemimegalencephaly in a 6.5-week-old infant with tuberous sclerosis complex.

Demitre Serletis, Carling MacDonald, Qi Xu, Colin J Kazina, Shyamala Dakshinamurti, Samantha Marin, Marc R Del Bigio.

  The aim of this report is to present a unique case of hemimegalencephaly and concomitant tuberous sclerosis complex (TSC1 mutation) with severe neonatal-onset epilepsy, which successfully underwent an anatomical hemispherectomy at 6.5 weeks of age for refractory seizures. Genetic testing confirmed a rare pathogenic, sporadic, heterozygous c.2041 + 1G > A gene mutation in intron 16 of the TSC1 gene, diagnostic for tuberous sclerosis. Post-operatively, the infant remained seizure free for at least 1 year. Following recurrence of her seizures, she has continued on multiple anti-seizure medications and everolimus therapy. We review the pathological and molecular features of this condition and highlight the ethics of intervention and steps taken toward safe neurosurgical intervention in this very young infant.

Keywords:  Epilepsy; Hemispherectomy; Pediatrics; mTOR pathway

DOI:  https://doi.org/10.1007/s00381-021-05431-1
CNS Neurosci Ther. 2022 Jan 15.

Optimization and high-density array of stereoelectroencephalography-guided radiofrequency thermocoagulation for the treatment of pediatric tuberous sclerosis complex with epilepsy.

Tian Luo, Xinhua Wang, Ji Wang, Rui Zhao, Hao Li, Yuanfeng Zhou, Yi Wang.

   BACKGROUND: Tuberous sclerosis complex (TSC) is an autosomal dominant neurocutaneous syndrome involved in many organ systems. At the same time, epilepsy is the most common manifestation and more than 50% of TSC patients present with intractable epilepsy. This study investigated the efficacy and safety of optimized and high-density stereoelectroencephalography (SEEG) guided radiofrequency thermocoagulation (RF-TC) in treating TSC-related epilepsy.
METHODS: Nine TSC children with refractory epilepsy were treated with first-stage SEEG-Guided RF-TC, and four underwent second-stage-optimized high-density array of SEEG-Guided RF-TC. Patients' clinical data and postoperative outcomes were analyzed retrospectively.
RESULTS: The patients' median age at surgery was 4 years and 2 month (range from 3 years and 5 month to 16 years and 7 month). The mean age at surgery was 6.7 years old. Eight in 9 (88.9%) patients achieved complete remission after the final operation at half-year follow-up. Of seven patients with final postoperative time beyond 1 year, 6 (85.7%) reached completely seizure-free. No severe or long-term neurologic impairment existed in all nine patients.
CONCLUSION: Optimized high-density array of SEEG-guided RF-TC is a safe and highly effective approach and can be an alternative application applied for TSC patients with refractory epilepsy.

Keywords:  pediatric; radiofrequency thermocoagulation (RF-TC); stereoelectroencephalography (SEEG); tuberous sclerosis complex

DOI:  https://doi.org/10.1111/cns.13804
Mol Biol Cell. 2022 Jan 12. mbcE21060309

PP2A-dependent TFEB activation is blocked by PIKfyve-induced mTORC1 activity.

Junya Hasegawa, Emi Tokuda, Yao Yao, Takehiko Sasaki, Ken Inoki, Lois S Weisman.

Transcriptional factor EB (TFEB) is a master regulator of genes required for autophagy and lysosomal function. The nuclear localization of TFEB is blocked by the mechanistic target of rapamycin complex 1 (mTORC1)-dependent phosphorylation of TFEB at multiple sites including Ser-211. Here we show that inhibition of PIKfyve, which produces phosphatidylinositol 3,5-bisphosphate on endosomes and lysosomes, causes a loss of Ser-211 phosphorylation and concomitant nuclear localization of TFEB. We found that while mTORC1 activity toward S6K1, as well as other major mTORC1 substrates, is not impaired, PIKfyve inhibition specifically impedes the interaction of TFEB with mTORC1. This suggests that mTORC1 activity on TFEB is selectively inhibited due to loss of mTORC1 access to TFEB. In addition, we found that TFEB activation during inhibition of PIKfyve relies on the ability of protein phosphatase 2A (PP2A) but not calcineurin/PPP3, to dephosphorylate TFEB Ser-211. Thus, when PIKfyve is inhibited, PP2A is dominant over mTORC1 for control of TFEB phosphorylation at Ser-S211. Together these findings suggest that mTORC1 and PP2A have opposing roles on TFEB via phosphorylation and dephosphorylation of Ser-211, respectively, and further, that PIKfyve inhibits TFEB activity by facilitating mTORC1-dependent phosphorylation of TFEB.

DOI: https://doi.org/10.1091/mbc.E21-06-0309
J Clin Neurol. 2022 Jan;18(1): 71-78

Efficacy of the Ketogenic Diet for Pediatric Epilepsy According to the Presence of Detectable Somatic mTOR Pathway Mutations in the Brain.

Ara Ko, Nam Suk Sim, Han Som Choi, Donghwa Yang, Se Hee Kim, Joon Soo Lee, Dong Seok Kim, Jeong Ho Lee, Heung Dong Kim, Hoon-Chul Kang.

   BACKGROUND AND PURPOSE: A multifactorial antiepileptic mechanism underlies the ketogenic diet (KD), and one of the proposed mechanisms of action is that the KD inhibits the mammalian target of rapamycin (mTOR) pathway. To test this clinically, this study aimed to determine the efficacy of the KD in patients with pathologically confirmed focal cortical dysplasia (FCD) due to genetically identifiable mTOR pathway dysregulation.
METHODS: A cohort of patients with pathologically confirmed FCD after epilepsy surgery and who were screened for the presence of germline and somatic mutations related to the mTOR pathway in peripheral blood and resected brain tissue was constructed prospectively. A retrospective review of the efficacy of the prior KD in these patients was performed.
RESULTS: Twenty-five patients with pathologically confirmed FCD and who were screened for the presence of detectable somatic mTOR pathway mutations had received a sufficient KD. Twelve of these patients (48.0%) had germline or somatic detectable mTOR pathway mutations. A response was defined as a ≥50% reduction in seizure frequency. The efficacy of the KD after 3 months of dietary therapy was superior in patients with detectable mTOR pathway mutations than in patients without detectable mTOR pathway mutations, although the difference was not statistically significant (responder rates of 58.3% vs. 38.5%, p=0.434).
CONCLUSIONS: A greater proportion of patients with mTOR pathway responded to the KD, but there was no statistically significant difference in efficacy of the KD between patients with and without detectable mTOR pathway mutations. Further study is warranted due to the smallness of the sample and the limited number of mTOR pathway genes tested in this study.

Keywords:  epilepsy; focal cortical dysplasia; ketogenic diet; mTORopathies; mammalian target of rapamycin; somatic mutation

DOI:  https://doi.org/10.3988/jcn.2022.18.1.71
Curr Drug Targets. 2022 Jan 11.

Targeting mTOR Signaling in Type 2 Diabetes Mellitus and Diabetes Complications.

Lin Yang, Zhixin Zhang, Doudou Wang, Yu Jiang, Ying Liu.

  The mechanistic target of rapamycin (mTOR) is a pivotal regulator of cell metabolism and growth. In the form of two different multi-protein complexes, mTORC1 and mTORC2, mTOR integrates cellular energy, nutrient and hormonal signals to regulate cellular metabolic homeostasis. In type 2 diabetes mellitus (T2DM) aberrant mTOR signaling underlies its pathological conditions and end-organ complications. Substantial evidence suggests that two mTOR-mediated signaling schemes, mTORC1-p70S6 kinase 1 (S6K1) and mTORC2-protein kinase B (AKT), play a critical role in insulin sensitivity and that their dysfunction contributes to development of T2DM. This review summaries our current understanding of the role of mTOR signaling in T2DM and its associated complications, as well as the potential use of mTOR inhibitors in treatment of T2DM.

Keywords:  diabetes complications; mTOR inhibitor; mTORC1; mTORC2; type 2 diabetes mellitus

DOI:  https://doi.org/10.2174/1389450123666220111115528
Turk Arch Pediatr. 2021 Jul;56(4): 356-365

Neurodevelopmental Findings and Epilepsy in Malformations of Cortical Development.

Olcay Şah, Dilşad Türkdoğan, Selda Küçük, Gülnur Takış, Ruslan Asadov, Gülten Öztürk, Olcay Ünver, Gazanfer Ekinci.

   Aim: The purpose of this study is to classify the malformations of cortical development in children according to the embryological formation, localization, and neurodevelopmental findings. Seizure/epilepsy and electrophysiological findings have also been compared.
Material and Methods: Seventy-five children (age: 1 month-16.5 years; 56% male) followed with the diagnosis of malformation of cortical development, in Marmara University Pendik Research and Educational Hospital Department of Pediatric Neurology, were included in the study. Their epilepsy characteristics, electroencephalogram (EEG) findings, and prognosis were reported. Neurodevelopmental characteristics were evaluated by the Bayley Scales of Infant and Toddler Development (Bayley-III) for the ages of 0-42 months (n = 30); the Denver Developmental Screening Test-II (DDST-II) for ages 42 months-6 years (n = 11); and the Wechsler Intelligence Scales for Children (WISC-R), used for children 6 years and older (n = 34).
Results: The patients were classified as 44% premigrational (14.6% microcephaly, 24% tuberous sclerosis, 2.7% focal cortical dysplasia, 1.3% hemimegalencephaly, and 1.3% diffuse cortical dysgenesis); 17.3% migrational (14.6% lissencephaly, 2.7% heterotopia); and 38.6% postmigrational (14.6% schizencephaly, 24% polymicrogyria) developmentally. According to involved area, the classification was 34.7% hemispheric/multilobar, 33.3% diffuse, and 32% focal. Seventy-five percent of the patients had a history of epilepsy, and 92% were resistant to treatment. The seizures started before the age of 12 months in diffuse malformations, and epileptic encephalopathy was more common in microcephaly with a rate of 80% and lissencephaly with a rate of 54.5% in the first EEGs. Ninety-five percent of patients had at least one level of neurodevelopmental delay detected by DDST/Bayley-III; this was more common in patients with accompanying epilepsy (P < .05). As seen more commonly in patients with diffuse pathologies and intractable frequent seizures, mental retardation was detected by WISC-R in 64.5% of patients (P < .05).
Conclusion: In cases with cortical developmental malformation, epilepsy/EEG features and neurodevelopmental prognosis can be predicted depending on the developmental process and type and extent of involvement. Patients should be followed up closely with EEG.

Keywords:  Barkovich 2012 classification; Bayley-III; DDST-II; Malformations of cortical development; WISC-R; epilepsy

DOI:  https://doi.org/10.5152/TurkArchPediatr.2021.20148
Proc Natl Acad Sci U S A. 2022 Jan 18. pii: e2110917119. [Epub ahead of print]119(3):

GATOR2 complex-mediated amino acid signaling regulates brain myelination.

Zongyan Yu, Zhiwen Yang, Guoru Ren, Yingjie Wang, Xiang Luo, Feiyan Zhu, Shouyang Yu, Lanlan Jia, Mina Chen, Paul F Worley, Bo Xiao.

  Amino acids are essential for cell growth and metabolism. Amino acid and growth factor signaling pathways coordinately regulate the mechanistic target of rapamycin complex 1 (mTORC1) kinase in cell growth and organ development. While major components of amino acid signaling mechanisms have been identified, their biological functions in organ development are unclear. We aimed to understand the functions of the critically positioned amino acid signaling complex GAP activity towards Rags 2 (GATOR2) in brain development. GATOR2 mediates amino acid signaling to mTORC1 by directly linking the amino acid sensors for arginine and leucine to downstream signaling complexes. Now, we report a role of GATOR2 in oligodendrocyte myelination in postnatal brain development. We show that the disruption of GATOR2 complex by genetic deletion of meiosis regulator for oocyte development (Mios, encoding a component of GATOR2) selectively impairs the formation of myelinating oligodendrocytes, thus brain myelination, without apparent effects on the formation of neurons and astrocytes. The loss of Mios impairs cell cycle progression of oligodendrocyte precursor cells, leading to their reduced proliferation and differentiation. Mios deletion manifests a cell type-dependent effect on mTORC1 in the brain, with oligodendroglial mTORC1 selectively affected. However, the role of Mios/GATOR2 in oligodendrocyte formation and myelination involves mTORC1-independent function. This study suggests that GATOR2 coordinates amino acid and growth factor signaling to regulate oligodendrocyte myelination.

Keywords:  GATOR2; Mios; amino acid signaling; myelination; oligodendrocytes

DOI:  https://doi.org/10.1073/pnas.2110917119
PLoS One. 2022 ;17(1): e0262576

Thermal stress affects proliferation and differentiation of turkey satellite cells through the mTOR/S6K pathway in a growth-dependent manner.

Jiahui Xu, Gale M Strasburg, Kent M Reed, Sandra G Velleman.

Satellite cells (SCs) are stem cells responsible for post-hatch muscle growth through hypertrophy and in birds are sensitive to thermal stress during the first week after hatch. The mechanistic target of rapamycin (mTOR) signaling pathway, which is highly responsive to thermal stress in differentiating turkey pectoralis major (p. major) muscle SCs, regulates protein synthesis and the activities of SCs through a downstream effector, S6 kinase (S6K). The objectives of this study were: 1) to determine the effect of heat (43°C) and cold (33°C) stress on activity of the mTOR/S6K pathway in SCs isolated from the p. major muscle of one-week-old faster-growing modern commercial (NC) turkeys compared to those from slower-growing Randombred Control Line 2 (RBC2) turkeys, and 2) to assess the effect of mTOR knockdown on the proliferation, differentiation, and expression of myogenic regulatory factors of the SCs. Heat stress increased phosphorylation of both mTOR and S6K in both turkey lines, with greater increases observed in the RBC2 line. With cold stress, greater reductions in mTOR and S6K phosphorylation were observed in the NC line. Early knockdown of mTOR decreased proliferation, differentiation, and expression of myoblast determination protein 1 and myogenin in both lines independent of temperature, with the RBC2 line showing greater reductions in proliferation and differentiation than the NC line at 38° and 43°C. Proliferating SCs are more dependent on mTOR/S6K-mediated regulation than differentiating SCs. Thus, thermal stress can affect breast muscle hypertrophic potential by changing satellite cell proliferation and differentiation, in part, through the mTOR/S6K pathway in a growth-dependent manner. These changes may result in irreversible effects on the development and growth of the turkey p. major muscle.

DOI: https://doi.org/10.1371/journal.pone.0262576
J Oncol Pharm Pract. 2022 Jan 12. 10781552211073673

Biomarkers of everolimus efficacy in breast cancer therapy.

Ioannis A Voutsadakis.

   OBJECTIVE: Everolimus is an inhibitor of serine/ threonine kinase mTOR. The drug is approved for the treatment of metastatic ER positive, HER2 negative breast cancers and benefits a subset of patients with these breast cancers in combination with hormonal therapies. Despite extensive efforts, no additional predictive biomarkers to guide therapeutic decisions for everolimus have been introduced in clinical practice.
DATA SOURCES: This paper discusses predictive biomarkers for everolimus efficacy in breast cancer. A search of the medline and web of science databases was performed using the words "everolimus" and "biomarkers". References of retrieved articles were manually scanned for additional relevant articles.
DATA SUMMARY: Everolimus benefits a subset of patients with metastatic ER positive, HER2 negative breast cancers in combination with hormonal therapies. Despite extensive efforts no additional predictive biomarkers to guide therapeutic decisions for everolimus therapy have been confirmed for use in clinical practice. However, promising biomarker leads for everolimus efficacy in breast cancer have been suggested and include expression of proteins in the mTOR pathway in ER positive, HER2 negative breast cancers. In HER2 positive cancers PIK3CA mutations, and PTEN expression loss are prognostic. Other clinical predictive biomarkers with more limited data include characteristics derived from whole genome sequencing, subsets of circulating leukocytes and changes in Standardized Uptake Values (SUV) of Positron Emission Tomography (PET) scans.
CONCLUSIONS: Putative predictive biomarkers for everolimus efficacy in breast cancer patients, both genomic and clinical, deserve further study and could lead to a better selection of responsive patients.

Keywords:  PI3 k; Rapalogs; metabolism; next generation sequencing; predictive biomarkers

DOI:  https://doi.org/10.1177/10781552211073673