DC 12: Cell-autonomous effects of activating RagGTPase mutants in heart and kidney

Project part of Work Package 2

Objectives: Outgrowths, tumors, cysts, renal, cardiac neurological defects and a compromised immune system are present in mTORopathies. Somatic mutations in RagC have been linked to fatal dilated cardiomyopathy, and various members of the MENTOR (Efeyan, Pende, Ballabio) have described life threatening pathologies in the kidney, in agreement with those observed in familial mTORopathies (Birt Hogg Dube and TSC). We have previously generated knock-in mice expressing activating mutations in RagA that mimics several features of mTORopathies. We have also KI activating mutations in RagC originally found in B-cell lymphomas, and such systemic expression of RagC mutations result in alterations in the heart that are consistent with dilated cardiomyopathy. In addition, these mice also exhibit multi-organ features of accelerated aging, and importantly for this proposal, progressive inflammation and other phenotypic alterations in RagC-mutant kidneys. Understanding the cellular and molecular underpinnings of these pathologies is somehow obscured by the pleiotropic effects that RagC mutations have on immune cells and on inflammation. We want to dissect the effects that are cell-autonomous in the kidney and heart parenchyma, thus mirroring somatic mutations in cells from these two organs, and in contrast to those systemic effects secondarily driven by deregulation of inflammatory cells. This will be followed by the dissection of the molecular mechanisms underlying such alterations by means of primary cultures and organoids derived from these models under hypothesis-driven and unbiased – omics interrogation. We will then test genetic epistasis and selected compounds in vitro and in vivo.

Expected Results: Establish the consequences of activation of the Rag GTPase axis in two tissues severely affected in mTORopathies, and dissect, in the context of this network and in collaboration with members of Work package 1 and Work package 2 (Dr. M. Pende, Prof. A. Ballabio) molecular routes downstream of the activation of RagC hopefully amenable of pharmacological targeting through parallel work in WP3.

Prospects of career development: The Efeyan Lab has trained 3 PhD students, who have all published impactful first-author papers and all continue to do research with a postdoctoral position, plus 4 ongoing thesis. In addition, other former trainees have moved into independent academic positions, positions in Pharma, or continue in academia under additional training phases in their path to independence.

Planned secondments: 3 months at Fondazione Telethon (TIGEM) to conduct high-content imaging for TFEB, and to assess transcriptional output of TFEB. 3 months at Mimetas for kidney-on-chip cultures from RagC and RagC mutant mice.