Publications (11) View all
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Article: Prenatal Rapamycin Results in Early and Late Behavioral Abnormalities in Wildtype C57Bl/6 Mice.
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ABSTRACT: Mammalian target of rapamycin (mTOR) signaling has been shown to be deregulated in a number of genetic, neurodevelopmental disorders including Tuberous Sclerosis Complex, Neurofibromatosis, Fragile X, and Rett syndromes. As a result, mTOR inhibitors, such as rapamycin and its analogs, offer potential therapeutic avenues for these disorders. Some of these disorders-such as Tuberous Sclerosis Complex-can be diagnosed prenatally. Thus, prenatal administration of these inhibitors could potentially prevent the development of the devastating symptoms associated with these disorders. To assess the possible detrimental effects of prenatal rapamycin treatment, we evaluated both early and late behavioral effects of a single rapamycin treatment at embryonic day 16.5 in wildtype C57Bl/6 mice. This treatment adversely impacted early developmental milestones as well as motor function in adult animals. Rapamycin also resulted in anxiety-like behaviors during both early development and adulthood but did not affect adult social behaviors. Together, these results indicate that a single, prenatal rapamycin treatment not only adversely affects early postnatal development but also results in long lasting negative effects, persisting into adulthood. These findings are of importance in considering prenatal administration of rapamycin and related drugs in the treatment of patients with neurogenetic, neurodevelopmental disorders.Behavior Genetics 12/2012; · 2.52 Impact Factor -
Article: Regulable neural progenitor-specific Tsc1 loss yields giant cells with organellar dysfunction in a model of tuberous sclerosis complex.
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ABSTRACT: Tuberous sclerosis complex (TSC) is a multiorgan genetic disease in which brain involvement causes epilepsy, intellectual disability, and autism. The hallmark pathological finding in TSC is the cerebral cortical tuber and its unique constituent, giant cells. However, an animal model that replicates giant cells has not yet been described. Here, we report that mosaic induction of Tsc1 loss in neural progenitor cells in Tsc1(cc) Nestin-rtTA(+) TetOp-cre(+) embryos by doxycycline leads to multiple neurological symptoms, including severe epilepsy and premature death. Strikingly, Tsc1-null neural progenitor cells develop into highly enlarged giant cells with enlarged vacuoles. We found that the vacuolated giant cells had multiple signs of organelle dysfunction, including markedly increased mitochondria, aberrant lysosomes, and elevated cellular stress. We found similar vacuolated giant cells in human tuber specimens. Postnatal rapamycin treatment completely reversed these phenotypes and rescued the mutants from epilepsy and premature death, despite prenatal onset of Tsc1 loss and mTOR complex 1 activation in the developing brain. This TSC brain model provides insights into the pathogenesis and organelle dysfunction of giant cells, as well as epilepsy control in patients with TSC.Proceedings of the National Academy of Sciences 11/2011; 108(45):E1070-9. · 9.68 Impact Factor -
Article: Therapeutic value of prenatal rapamycin treatment in a mouse brain model of tuberous sclerosis complex.
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ABSTRACT: Epileptic seizures, particularly infantile spasms, are often seen in infants with tuberous sclerosis complex (TSC) soon after birth. It is feared that there are long-term developmental and cognitive consequences from ongoing, frequent epilepsy. In addition, the hallmark brain pathology of TSC, cortical tubers and giant cells are fully developed at late gestational ages. These observations have led us to examine the benefit of prenatal rapamycin in a new fetal brain model of TSC. In this Tsc1(cc) Nes-cre(+) mouse model, recombination and loss of Tsc1 in neural progenitor cells leads to brain enlargement, hyperactivation of mTOR, and neonatal death on P0 due to reduced pup-maternal interaction. A single dose of prenatal rapamycin given to pregnant dams (1 mg/kg, subcutaneous) rescued the lethality of mutant mice. This one dose of prenatal rapamycin treatment reduced hyperactivation of the mTOR pathway in the mutant brain without causing apparent pregnancy loss. Continued postnatal rapamycin beginning at day 8 extended the survival of these mice to a median of 12 days with complete suppression of hyperactive mTOR. However, the rapamycin-treated mutants developed enlarged brains with an increased number of brain cells, displaying marked runting and developmental delay. These observations demonstrate the therapeutic benefit and limitations of prenatal rapamycin in a prenatal-onset brain model of TSC. Our data also suggest the possibility and limitations of this approach for TSC infants and mothers.Human Molecular Genetics 09/2011; 20(23):4597-604. · 7.64 Impact Factor -
Article: Mammalian target of rapamycin up-regulation of pyruvate kinase isoenzyme type M2 is critical for aerobic glycolysis and tumor growth.
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ABSTRACT: Although aerobic glycolysis (the Warburg effect) is a hallmark of cancer, key questions, including when, how, and why cancer cells become highly glycolytic, remain less clear. For a largely unknown regulatory mechanism, a rate-limiting glycolytic enzyme pyruvate kinase M2 (PKM2) isoform is exclusively expressed in embryonic, proliferating, and tumor cells, and plays an essential role in tumor metabolism and growth. Because the receptor tyrosine kinase/PI3K/AKT/mammalian target of rapamycin (RTK/PI3K/AKT/mTOR) signaling cascade is a frequently altered pathway in cancer, we explored its potential role in cancer metabolism. We identified mTOR as a central activator of the Warburg effect by inducing PKM2 and other glycolytic enzymes under normoxic conditions. PKM2 level was augmented in mouse kidney tumors due to deficiency of tuberous sclerosis complex 2 and consequent mTOR activation, and was reduced in human cancer cells by mTOR suppression. mTOR up-regulation of PKM2 expression was through hypoxia-inducible factor 1α (HIF1α)-mediated transcription activation, and c-Myc-heterogeneous nuclear ribonucleoproteins (hnRNPs)-dependent regulation of PKM2 gene splicing. Disruption of PKM2 suppressed oncogenic mTOR-mediated tumorigenesis. Unlike normal cells, mTOR hyperactive cells were more sensitive to inhibition of mTOR or glycolysis. Dual suppression of mTOR and glycolysis synergistically blunted the proliferation and tumor development of mTOR hyperactive cells. Even though aerobic glycolysis is not required for breach of senescence for immortalization and transformation, the frequently deregulated mTOR signaling during multistep oncogenic processes could contribute to the development of the Warburg effect in many cancers. Components of the mTOR/HIF1α/Myc-hnRNPs/PKM2 glycolysis signaling network could be targeted for the treatment of cancer caused by an aberrant RTK/PI3K/AKT/mTOR signaling pathway.Proceedings of the National Academy of Sciences 02/2011; 108(10):4129-34. · 9.68 Impact Factor -
Article: Smooth muscle protein-22-mediated deletion of Tsc1 results in cardiac hypertrophy that is mTORC1-mediated and reversed by rapamycin.
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ABSTRACT: Constitutive activation of mammalian target of rapamycin complex 1 (mTORC1), a key kinase complex that regulates cell size and growth, is observed with inactivating mutations of either of the tuberous sclerosis complex (TSC) genes, Tsc1 and Tsc2. Tsc1 and Tsc2 are highly expressed in cardiovascular tissue but their functional role there is unknown. We generated a tissue-specific knock-out of Tsc1, using a conditional allele of Tsc1 and a cre recombinase allele regulated by the smooth muscle protein-22 (SM22) promoter (Tsc1c/cSM22cre+/-) to constitutively activate mTOR in cardiovascular tissue. Significant gene recombination (∼80%) occurred in the heart by embryonic day (E) 15, and reduction in Tsc1 expression with increased levels of phosphorylated S6 kinase (S6K) and S6 was observed, consistent with constitutive activation of mTORC1. Cardiac hypertrophy was evident by E15 with post-natal progression to heart weights of 142 ± 24 mg in Tsc1c/cSM22cre+/- mice versus 65 ± 14 mg in controls (P < 0.01). Median survival of Tsc1c/cSM22cre+/- mice was 24 days, with none surviving beyond 6 weeks. Pathologic and echocardiographic analysis revealed severe biventricular hypertrophy without evidence of fibrosis or myocyte disarray, and significant reduction in the left ventricular end-diastolic diameter (P < 0.001) and fractional index (P < 0.001). Inhibition of mTORC1 by rapamycin resulted in prolonged survival of Tsc1c/cSM22cre+/- mice, with regression of ventricular hypertrophy. These data support a critical role for the Tsc1/Tsc2-mTORC1-S6K axis in the normal development of cardiovascular tissue and also suggest possible therapeutic potential of rapamycin in cardiac disorders where pathologic mTORC1 activation occurs.Human Molecular Genetics 01/2011; 20(7):1290-305. · 7.64 Impact Factor
