# Mechanisms of mTOR-independent axon growth and guidance defects in TSC2 mutant human neurons

> **NIH NIH R01** · UNIVERSITY OF WISCONSIN-MADISON · 2022 · $352,904

## Abstract

Growing evidence suggests that patients with Tuberous Sclerosis Complex (TSC), like other neuro-developmental disorders, have mis-wiring of neuronal connections that form during development. These
defects in neuronal connectivity likely contribute to symptoms of TSC, such as cognitive deficits, autism and
epilepsy. However, defective axon guidance by human neurons has only been suggested from brain imaging
studies, as models to study the molecular basis for mis-guidance of developing human neurons have not been
developed. To directly address these fundamental questions, we will study the development of human neurons
that we differentiate from human induced pluripotent stem cells (hiPSCs) from TSC patient-derived cells and
their genetically engineered counterparts. Using a series of cell behavior and molecular signaling assays, we
will compare TSC2 mutant neurons with their gene-corrected, isogenic control neurons both in vitro and within
3D forebrain spheroids. We will examine changes in mTORC1 and mTORC2 signaling pathways in TSC2
mutant neurons to determine the relative contributions of each signaling pathway to neuronal development.
While modulation of mTOR-dependent protein synthesis has been suggested to be required downstream of
both attractive and repulsive axon guidance in several animal model systems, it is unknown if similar
mechanisms function in developing human neurons. Our surprising preliminary data suggest that TSC2
functions independent of mTOR in growth cones to directly regulate the cytoskeleton to control axon guidance.
In this proposal, we will determine how loss of TSC2 function alters the development of human forebrain
neurons, with a current focus on axon extension and sensitivity to key axon guidance cues, two important
cellular consequences of abnormal TSC2 function. We will determine the molecular mechanisms downstream
of TSC2 and test functionally how these signaling pathway contribute to abnormal axon extension and
guidance cue responses. Over the long term, we believe our research may help identify key druggable targets
in patients with TSC.

## Key facts

- **NIH application ID:** 10397403
- **Project number:** 5R01NS113314-03
- **Recipient organization:** UNIVERSITY OF WISCONSIN-MADISON
- **Principal Investigator:** Timothy M Gomez
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $352,904
- **Award type:** 5
- **Project period:** 2020-05-01 → 2025-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10397403

## Citation

> US National Institutes of Health, RePORTER application 10397403, Mechanisms of mTOR-independent axon growth and guidance defects in TSC2 mutant human neurons (5R01NS113314-03). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10397403. Licensed CC0.

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