bims-tubesc Biomed News
on Molecular mechanisms in tuberous sclerosis
Issue of 2021‒07‒11
twelve papers selected by
Marti Cadena Sandoval

  1. Orphanet J Rare Dis. 2021 Jul 06. 16(1): 301
      BACKGROUND: Tuberous sclerosis complex (TSC) is a rare multisystem autosomal dominant disorder caused by pathogenic variants in either the TSC1 or TSC2 gene. Common manifestations of TSC have been grouped into major and minor clinical diagnostic criteria and assessed in clinical routine workup. However, case studies point towards the existence of rare disease manifestations and to the potential association of TSC with malignant tumors. In this study we sought to characterize rare manifestations and malignancies using a large cohort of patients.METHODS: TuberOus SClerosis registry to increAse disease awareness (TOSCA) is a multicenter, international disease registry collecting clinical manifestations and characteristics of patients with TSC, both retrospectively and prospectively. We report rates and characteristics of rare manifestations and malignancies in patients with TSC who had enrolled in the TOSCA registry. We also examined these manifestations by age, sex, and genotype (TSC1 or TSC2).
    RESULTS: Overall, 2211 patients with TSC were enrolled in the study. Rare manifestations were reported in 382 (17.3%) study participants and malignancies in 65 (2.9%). Of these rare manifestations, the most frequent were bone sclerotic foci (39.5%), scoliosis (23%), thyroid adenoma (5.5%), adrenal angiomyolipoma (4.5%), hemihypertrophy and pancreatic neuroendocrine tumors (pNET; both 3.1%). These rare manifestations were more commonly observed in adults than children (66.2% vs. 22.7%), in females versus males (58.4% vs. 41.6%; except for scoliosis: 48.9% vs. 51.1%), and in those with TSC2 versus TSC1 (67.0% vs. 21.1%; except for thyroid adenoma: 42.9% vs. 57.1%). In the 65 individuals with reported malignancies, the most common were renal cell carcinoma (47.7%), followed by breast (10.8%) and thyroid cancer (9.2%). Although malignancies were more common in adult patients, 26.1% were reported in children and 63.1% in individuals < 40 years. TSC1 mutations were over-represented in individuals with malignancies compared to the overall TOSCA cohort (32.1% vs. 18.5%).
    CONCLUSION: Rare manifestations were observed in a significant proportion of individuals with TSC. We recommend further examination of rare manifestations in TSC. Collectively, malignancies were infrequent findings in our cohort. However, compared to the general population, malignant tumors occurred earlier in age and some tumor types were more common.
    Keywords:  Malignancy; Rare manifestation; TOSCA; TSC; Tuberous sclerosis complex
  2. Mymensingh Med J. 2021 Jul;30(3): 850-854
      Angiomyolipomas (AML) are benign tumor of kidney also referred as renal hamartoma composed of varying amounts of mature adipose tissue, smooth muscle, and blood vessels. It is seen in two distinct clinical forms, a sporadic (isolated) form and 55-80% seen in association with Tuberous sclerosis complex (TSC). If the lesion grows to a large size, a series of clinical manifestations and serious complications may occur. Here we present a case of 26 years lady who presented in the Department Radiology & Imaging of Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh with chief complaints of bilateral loin pain and occasional hematuria for 2 months. Ultrasound abdomen and contrast enhanced computed tomography shows bilateral renal angiomyolipoma (left>right). In order to look for tuberous sclerosis features, we followed her with plain computed tomography of head which shows subependymal calcifications.
  3. Orphanet J Rare Dis. 2021 Jul 03. 16(1): 299
      PURPOSE: To evaluate the efficacy and safety of everolimus and sirolimus in patients with tuberous sclerosis complex-associated angiomyolipomas (TSC-AML).MATERIALS AND METHODS: We performed a multi-institutional retrospective study of TSC-AML patients treated with oral everolimus 10 mg or sirolimus 2 mg per day for at least 3 months. Angiomyolipoma volume was estimated using orthogonal measurements by MRI or CT. Adverse events (AEs) were assessed according to the National Cancer Institute Common Terminology Criteria for Adverse Events. All analyses were performed using SPSS 19.0 software.
    RESULTS: Response rates were high in both groups. With the prolonged medication durations, the therapeutic efficacy of both agents became more significant. The TSC-AML volume reduction after 6 and 12 months was more pronounced in patients with everolimus than those with sirolimus. More than half of the patients treated with everolimus had ≥ 50% reduction, and approximately 80% of them had ≥ 30% reduction, which was higher than that in patients treated with sirolimus. Regarding safety, there was no significant difference in the incidence of AEs between the two groups.
    CONCLUSIONS: Both everolimus and sirolimus are excellent therapeutic options for TSC-AML. However, everolimus has a better therapeutic efficacy than sirolimus, particularly in reducing TSC-AML volume. Everolimus is therefore recommended as the first choice of therapy for TSC-AML.
    Keywords:  Adverse events; Everolimus; Sirolimus; Treatment outcome; Tuberous sclerosis complex
  4. J Med Case Rep. 2021 Jul 05. 15(1): 334
      BACKGROUND: Rhabdomyomas comprise the majority of cardiac tumors in fetuses and are found in association with tuberous sclerosis complex. More than 90% of fetuses and neonates with multiple cardiac rhabdomyomas have signs of tuberous sclerosis complex. However, solitary cardiac rhabdomyoma cases are largely unrelated to tuberous sclerosis complex. Here, we report a case involving multiple cardiac rhabdomyomas not associated with tuberous sclerosis complex in a dizygotic twin.CASE PRESENTATION: A 36-year-old Japanese woman was diagnosed with a dizygotic twin pregnancy in the first trimester. Consistent with dizygosity, the fetal sex was discordant (male and female). At 27 weeks of gestation, hydrops and multiple echogenic cardiac masses were noted in the male baby, with the largest mass measuring 34 × 30 mm. The female fetus appeared normal. The cardiac masses enlarged gradually with the progression of the hydrops. At 32 weeks of gestation, intrauterine death of the male fetus was confirmed. The next day, autopsy of the male fetus was performed after cesarean section. Three well-demarcated white-tan-colored nodules were formed in the ventricular walls and interventricular septum, with the largest nodule (40 × 30 mm) in the left ventricular wall. Histologically, these lesions were diagnosed as rhabdomyomas.
    CONCLUSIONS: We encountered a case involving multiple cardiac rhabdomyomas arising in one of dizygotic twin fetuses. Unlike most reported cases of multiple cardiac rhabdomyomas, this case was not accompanied by tuberous sclerosis complex. To the best of our knowledge, this is the first case report of multiple cardiac rhabdomyomas that developed in only one of dizygotic twins in the English literature.
    Keywords:  Autopsy; Cardiac rhabdomyoma; Dizygotic twin; Tuberous sclerosis complex
  5. iScience. 2021 Jul 23. 24(7): 102684
      Tuberous sclerosis (TS) is a rare disorder exhibiting multi-systemic benign neoplasms. We hypothesized the origin of TS neoplastic cells derived from the neural crest given the heterogeneous ecto-mesenchymal phenotype of the most common TS neoplasms. To test this hypothesis, we employed Cre-loxP lineage tracing of myelin protein zero (Mpz)-expressing neural crest cells (NCCs) in spontaneously developing renal tumors of Tsc2 +/- /Mpz(Cre)/TdT fl/fl reporter mice. In these mice, ectopic renal tumor onset was detected at 4 months of age increasing in volume by 16 months of age with concomitant increase in the subpopulation of tdTomato+ NCCs from 0% to 6.45% of the total number of renal tumor cells. Our results suggest that Tsc2 +/- mouse renal tumors arise from domiciled proliferative progenitor cell populations of neural crest origin that co-opt tumorigenesis due to mutations in Tsc2 loci. Targeting neural crest antigenic determinants will provide a potential alternative therapeutic approach for TS pathogenesis.
    Keywords:  cancer;; molecular physiology; stem cells research
  6. Front Hum Neurosci. 2021 ;15 680295
      Objectives: To evaluate the value of fast ripples (FRs) (200-500 Hz) recorded with stereo-electroencephalograph (SEEG) in the localization of epileptogenic tubers in patients with tuberous sclerosis complex (TSC). Methods: Seventeen TSC patients who underwent preoperative SEEG examination and resective epilepsy surgery were retrospectively enrolled. They were divided into two groups according to the seizure control at 1-year postoperative follow-up. The occurrence frequencies of FRs were automatically counted, and the FR rate was calculated. The high FR rate was defined as FR rate ≧0.5. According to different positions, the contacts' locations were divided into three groups: inner of the tubers, the junction region of the tubers, and out of the tubers. The influence factors of postoperative seizure freedom were also analyzed. Results: Twelve patients reached postoperative seizure freedom at 1-year follow-up. In total, FRs were found in 24.2% of the contacts and 67.1% of the tubers in all assessed patients. There were 47 high FR rate contacts localized in the junction region of the tubers, which was 62.7% of the 75 high FR rate contacts in total and was 8.4% of the total 561 contacts localized in the junction region of the tubers. Total removal of epileptogenic tubers and total resection of the high FR rate tubers/contacts were associated with postoperative seizure freedom (P < 0.05). Conclusion: FRs could be extensively detected in TSC patients using SEEG, and high FR rate contacts were mostly localized in the junction region of the epileptogenic tuber, which could aid in the localization of epileptogenic tubers.
    Keywords:  epilepsy surgery; epileptogenic zone; fast ripples; stereo-electroencephalography(SEEG); tuberous sclerosis complex
  7. Mol Metab. 2021 Jul 02. pii: S2212-8778(21)00131-9. [Epub ahead of print] 101286
      OBJECTIVE: Crinophagy is a secretory granule-specific autophagic process that regulates hormone content and secretion in endocrine cells. However, despite being one of the earliest described autophagic processes, its mechanism of action and regulation in mammalian cells remains unclear.METHODS AND RESULTS: Here, we examined mammalian crinophagy and its modulation regulate hormone secretion in a glucagon-producing mouse pancreatic α-cell line, alpha TC1 clone 9 (αTC9) and in vivo. Western blot, electron microscopy and immunofluorescence analyses were performed to study crinophagy and glucagon secretion in αTC9 cells and C57BL/6 mice, in response to the mammalian target of rapamycin complex 1 (MTORC1) inhibitor rapamycin. Amino acid depletion and pharmacological inhibition of MTORC1 increased the shuttling of glucagon-containing secretory granules into lysosomes for crinophagic degradation to reduce glucagon secretion via a macroautophagy-independent mechanism. Furthermore, MTORC1 inhibition reduced both intracellular and secreted glucagon in rapamycin-treated mice, in response to hypoglycaemia.
    CONCLUSION: In summary, we have identified a novel crinophagic mechanism of intracellular glucagon turnover in pancreatic α-cells regulated by MTORC1 signaling.
    Keywords:  Autophagy; Crinophagy; Diabetes; Glucagon; Lysosomes; MTORC1; Rapamycin
  8. Zool Res. 2021 Jul 18. pii: 2095-8137(2021)04-0482-05. [Epub ahead of print]42(4): 482-486
      Retinitis pigmentosa (RP) is an inherited retinal degenerative disease that begins with defective rod photoreceptor function, followed by impaired cone function, and complete blindness in its late stage. To date, however, there is no effective treatment for RP. By carrying a nonsense mutation in the Pde6b gene, rd1 mice display elevated cGMP in conjunction with higher intracellular Ca 2+ in their rod photoreceptors, resulting in fast retinal degeneration. Ca 2+ has been linked to activation of the mammalian target of rapamycin (mTOR) pathway. The mTOR pathway integrates extracellular and intracellular signals to sense the supply of nutrients and plays a central role in regulating protein and lipid synthesis as well as apoptosis and autophagy. In the present study, we showed that mTOR and phosphorylated mTOR (p-mTOR, activated form of mTOR) are up-regulated in rd1 photoreceptors at postnatal day 10 (P10), a pre-degenerative stage. Moreover, the downstream effectors of mTOR, such as pS6K and S6K, are also increased, suggesting activation of the mTOR signaling pathway. Intravitreal administration of rapamycin, a negative regulator of mTOR, inhibits the mTOR pathway in rd1 photoreceptors. Consequently, the progression of retinal degeneration is slower and retinal function is enhanced, possibly mediated by activation of autophagy in the photoreceptors. Taken together, these results highlight rapamycin as a potential therapeutic avenue for retinal degeneration.
    Keywords:  Autophagy; Photoreceptors; Retinal degeneration; Retinitis pigmentosa; mTOR, Rapamycin; rd1
  9. Cell Signal. 2021 Jul 02. pii: S0898-6568(21)00161-3. [Epub ahead of print] 110072
      Function of mTORC1 and mTORC2 has emerged as a driver of mesangial cell pathologies in diabetic nephropathy. The mechanism of mTOR activation is poorly understood in this disease. Deptor is a constitutive subunit and a negative regulator of both mTOR complexes. Mechanistic investigation in mesangial cells revealed that high glucose decreased the expression of deptor concomitant with increased mTORC1 and mTORC2 activities, induction of hypertrophy and, expression of fibronectin and PAI-1. shRNAs against deptor mimicked these pathologic outcomes of high glucose. Conversely, overexpression of deptor significantly inhibited all effects of high glucose. To determine the mechanism of deptor suppression, we found that high glucose significantly increased the expression of EZH2, resulting in lysine-27 tri-methylation of histone H3 (H3K27Me3). Employing approaches including pharmacological inhibition, shRNA-mediated downregulation and overexpression of EZH2, we found that EZH2 regulates high glucose-induced deptor suppression along with activation of mTOR, mesangial cell hypertrophy and fibronectin/PAI-1 expression. Moreover, expression of hyperactive mTORC1 reversed shEZH2-mediated inhibition of hypertrophy and expression of fibronectin and PAI-1 by high glucose. Finally, in renal cortex of diabetic mice, we found that enhanced expression of EZH2 is associated with decreased deptor levels and increased mTOR activity and, expression of fibronectin and PAI-1. Together, our findings provide a novel mechanism for mTOR activation via EZH2 to induce mesangial cell hypertrophy and matrix expansion during early progression of diabetic nephropathy. These results suggest a strategy for leveraging the intrinsic effect of deptor to suppress mTOR activity via reducing EZH2 as a novel therapy for diabetic nephropathy.
    Keywords:  Diabetic renal hypertrophy; Kidney; Matrix expansion, EZH2, deptor; mTORC1
  10. Hepatology. 2021 Jul 07.
      BACKGROUND & AIMS: Non-alcoholic fatty liver disease (NAFLD) is the most common hepatic pathology in western countries and no treatment is currently available. NAFLD is characterized by the aberrant hepatocellular accumulation of fatty acids in the form of lipid droplets (LD). Recently, it was shown that liver LD degradation occurs via a process termed lipophagy; a novel form of autophagy. However, the molecular mechanisms governing liver lipophagy are elusive. Here, we aimed to ascertain the key molecular players that regulate hepatic lipophagy and their importance in NAFLD.APPROACH & RESULTS: We analyzed the formation and degradation of LD in vitro (fibroblasts and primary mouse hepatocytes), in vivo and ex vivo (mouse and human liver slices) and focused on the role of the autophagy master regulator mammalian Target Of Rapamycin Complex 1 (mTORC1) and the LD coating protein Plin3 in these processes. We show that the autophagy machinery is recruited to the LD upon hepatic overload of oleic acid in all experimental settings. This led to activation of lipophagy, a process that was abolished by Plin3 knockdown using RNA interference. Furthermore, Plin3 directly interacted with the autophagy proteins Fip200 and Atg16L, suggesting that Plin3 functions as a docking protein or is involved in autophagosome formation to activate lipophagy. Finally, we show that mTORC1 phosphorylated Plin3 to promote LD degradation.
    CONCLUSIONS: These results reveal that mTORC1 regulates liver lipophagy through a mechanism dependent on Plin3 phosphorylation. We propose that stimulating this pathway can enhance lipophagy in hepatocytes to help protect the liver from lipid-mediated toxicity, thus offering a new therapeutic strategy in NAFLD.
    Keywords:  autophagy; fatty liver disease; hepatocytes; lipid droplets; perilipin