Tuberous sclerosis complex–associated CNS abnormalities depend on hyperactivation of mTORC1 and Akt
Paola Zordan, … , Pietro L. Poliani, Rossella Galli
Paola Zordan, … , Pietro L. Poliani, Rossella Galli
Published February 1, 2018
Citation Information: J Clin Invest. 2018;128(4):1688-1706. https://doi.org/10.1172/JCI96342.
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Research Article Neuroscience

Tuberous sclerosis complex–associated CNS abnormalities depend on hyperactivation of mTORC1 and Akt

Abstract

Tuberous sclerosis complex (TSC) is a dominantly inherited disease caused by hyperactivation of the mTORC1 pathway and characterized by the development of hamartomas and benign tumors, including in the brain. Among the neurological manifestations associated with TSC, the tumor progression of static subependymal nodules (SENs) into subependymal giant cell astrocytomas (SEGAs) is one of the major causes of morbidity and shortened life expectancy. To date, mouse modeling has failed in reproducing these 2 lesions. Here we report that simultaneous hyperactivation of mTORC1 and Akt pathways by codeletion of Tsc1 and Pten, selectively in postnatal neural stem cells (pNSCs), is required for the formation of bona fide SENs and SEGAs. Notably, both lesions closely recapitulate the pathognomonic morphological and molecular features of the corresponding human abnormalities. The establishment of long-term expanding pNSC lines from mouse SENs and SEGAs made possible the identification of mTORC2 as one of the mediators conferring tumorigenic potential to SEGA pNSCs. Notably, in spite of concurrent Akt hyperactivation in mouse brain lesions, single mTOR inhibition by rapamycin was sufficient to strongly impair mouse SEGA growth. This study provides evidence that, concomitant with mTORC1 hyperactivation, sustained activation of Akt and mTORC2 in pNSCs is a mandatory step for the induction of SENs and SEGAs, and, at the same time, makes available an unprecedented NSC-based in vivo/in vitro model to be exploited for identifying actionable targets in TSC.

Authors

Paola Zordan, Manuela Cominelli, Federica Cascino, Elisa Tratta, Pietro L. Poliani, Rossella Galli

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Figure 8

Postnatal NSCs isolated from SENs and SEGAs developing in TPN mice retain molecular and cellular features of their lesion of origin.

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Postnatal NSCs isolated from SENs and SEGAs developing in TPN mice retai...
(A) Phase contrast microphotographs highlight the increased adhesive behavior of mutant pNSCs as compared with controls (representative P15–17 TPN pNSCs line L1; original magnification, ×400). SEGA-derived pNSC cultures contained multinucleated cells (representative P15–17 TPN pNSCs line L90; red, cortactin; green, nestin; ×800). (B) Both undifferentiated and differentiated P10 and P15–17 TPN cultures (L22 and L1) showed higher pS6 phosphorylation and nestin expression than controls (L26 and L4) (×400). Abnormal expression of neuronal and glial markers, such as Tuj1, GFAP, and GalC-IR, was retrieved by IF in both undifferentiated and differentiated P10 and P15–17 mutant cultures as compared with controls (×400). Data are representative of 3 pairs of pNSC lines for each activation time. (C) WB of undifferentiated P10 and P15–17 pNSCs highlighted efficient deletion of Tsc1 (*specific band) and Pten as well as different hyperactivation of mTORC1, Akt, ERK, and mTORC2 in mutant versus control pNSCs, with pERK and mTORC2 being more activated in SEGA pNSCs than in SEN pNSCs.