Characterizing Tumor-Induced Ataxia in a Vestibular Schwannoma Mouse Model

Summary

We developed a panel of behavioral assays to study tumor-induced ataxia and to evaluate therapies that preserve neurological function in a mouse model of vestibular schwannoma.

Abstract

NF2-related schwannomatosis (NF2-SWN) is an autosomal dominant tumor predisposition syndrome caused by germline mutations in the NF2 tumor suppressor gene. The disease is characterized by the development of bilateral vestibular schwannomas (VSs), which progressively enlarge and result in hearing loss, imbalance, and ataxia-symptoms that profoundly affect patients' quality of life. No FDA-approved pharmacologic treatments are currently available. Among the neurological deficits, ataxia remains a particularly debilitating yet understudied manifestation, largely due to the lack of robust preclinical models for its evaluation. In this study, we developed a set of behavioral assays to systematically assess tumor-induced ataxia in an orthotopic mouse model of VS-associated hearing loss and ataxia. These tests allow quantitative measurement of balance and motor coordination deficits arising from tumor burden. This experimental platform enables mechanistic studies of tumor-induced cerebellar dysfunction and provides a valuable tool for preclinical evaluation of therapeutic strategies. By integrating behavioral assessments with tumor biology and hearing tests, this approach facilitates the characterization of both tumor-suppressive and neuroprotective treatment effects. Ultimately, these assays offer a versatile framework that can also be applied to other neurological disorders characterized by ataxia, expanding their utility beyond NF2-SWN.

Introduction

NF2-related schwannomatosis (NF2-SWN) is a rare, dominantly inherited tumor predisposition syndrome caused by mutations in the NF2 tumor suppressor gene, which encodes the cytoskeletal protein merlin¹. Loss of merlin function disrupts signaling pathways regulating cell proliferation, adhesion, and survival, predisposing affected individuals to the development of multiple benign tumors of the nervous system. The hallmark of NF2-SWN is the formation of bilateral vestibular schwannomas (VSs) - non-malignant Schwann cell-derived tumors that arise along the vestibulocochlear nerves. These tumors progressively enla....

Protocol

Animal experiments were conducted in accordance with the protocol approved by the Institutional Animal Care and Use Committee of Massachusetts General Brigham (MGB).

1. Animal model

1. Inoculate Nf2^-/- cells (murine Nf2^-/- Schwann cells expressing Gaussia luciferase reporter gene, Gluc) into immunocompetent C57/FVB mice. Using a stereotactic injection device (Figure 1A), inject each mouse with 1 µL of 2,500 tumor cells into the CPA region of the right hemisphere^4,6.
2. Use both male and female....

Results

CPA tumor growth causes ataxia in the VS mouse model

To evaluate tumor-induced ataxia, we established two experimental cohorts. First, to evaluate the effects of animal surgery and tumor cell implantation on ataxia, mice underwent sham surgery and injection of saline into the CPA region. Ataxia symptoms in the sham group mice were compared with those in unoperated control mice. In the second cohort, Nf2^-/- tumors were injected into the CPA region, and ataxi.......

Discussion

The behavioral assays described here provide a robust and quantitative framework for assessing ataxia and motor coordination deficits in mouse models of VS and related vestibular disorders. Adapted from established protocols for neurodegenerative disease models, such as Huntington's disease and spinocerebellar ataxias¹⁰, these tests are well-suited for characterizing tumor-induced vestibular dysfunction in NF2-SWN. By combining multiple behavioral.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Fetal bovine serum	ThermoFisher	A5670701
GloMax 96 Microplate Luminometer	Promega	GM3000
McKesson blue procedure underpad	McKesson	75402
Schwann cell growth supplement	ScienCell	1752