Defining the molecular epigenetic signature downstream of mTORC1 signaling

Tuberous sclerosis complex (TSC) is a multifaceted disease due to TSC1 or TSC2 loss causing tumors to grow in several organs especially the brain, the kidney (angiomyolipoma – AML), the lung (lymphangioleiomyomatosis – LAM). Aberrant activation of the mTORC1 signaling network (mechanistic Target of Rapamycin Complex I) underlies the development and progression of TSC. However, the molecular and pathological consequences of this activation are still largely unknown due, in part, to a lack of understanding of the downstream cellular processes regulated by mTORC1. Chromatin modifications have been well-recognized to play a critical role in the regulation of genome function. Many of these modifications are introduced and removed by enzymes that utilize molecules derived from cellular metabolism. Given that mTORC1 is a key regulator of diverse metabolic processes, we hypothesize that this signaling pathway can impinge on epigenetic modifications indirectly through regulation of cell metabolism and/or directly through regulation of epigenetic modulators supporting the growth of TSC-associated tumors. The major goal of this project is to uncover the influence of mTORC1 on the epigenetic landscape at the molecular level. To do so, I will unbiasedly assess the epigenome and epiproteome in various TSC deficient settings. This aim will help us to understand the molecular influence of mTORC1 on the epigenetic landscape, and whether these mTORC1-dependent alterations are occurring in TSC and LAM. My preliminary data demonstrate that the levels of the methyl donor S-adenosyl-methionine (SAM) are higher in TSC deficient cells than wild-type setting. I will assess whether mTORC1 contributes to epigenetic landscape remodeling by controlling the synthesis of SAM in a variety of TSC deficient cell settings. I will perform gene expression analysis, targeted steady-state metabolite profiling and isotopic tracing experiments. Finally, in the second aim, I propose to identify potential metabolic and epigenetic vulnerabilities that could be targeted in diseases where mTORC1 is hyperactivated such as TSC, AML and LAM. I propose to use metabolic inhibitors targeting the SAM pathway in combination with rapalogs to more efficiently eliminate TSC-driven tumors. Overall, the proposed project will upraise our basic understanding of the metabolic and epigenetic alterations arising in TSC downstream of mTORC1 and provide eventually new therapeutic strategies to fight TSC.