# Defining the role of Tox3 in congenital cerebellar hypoplasia and ataxia

> **NIH NIH R56** · CEDARS-SINAI MEDICAL CENTER · 2023 · $584,500

## Abstract

PROJECT SUMMARY / ABSTRACT
The cerebellum is an exquisitely laminated structure regulating the balance, voluntary motor coordination and
modulating language and cognition through connections with the forebrain. Sitting just under the forebrain,
cerebellum is estimated to contain roughly 80% of the neurons in the human brain. Accordingly, cerebellar
dysgenesis, pathology, or dysfunction is associated with a host of diseases or disorders, including ataxia,
autism, and intellectual deficit. Most cerebellar neurons are a subtype called cerebellar granule cells (CGCs),
which are generated embryonically from a structure termed the rhombic lip (RL)—a germinal zone residing at
the interface between the ventricular zone (VZ) and roof plate of the fourth ventricle. The mechanisms leading
to the specification of the RL germinal niche and subsequent generation of granule cells remain incompletely
understood. Specifically, the epigenetic and transcriptomic changes underlying how the ventricular zone
precursor cells choose the to become RL are largely unknown. We have generated a novel conditional
knockout (cKO) mouse for Tox3, a member of the TOX family of transcription factors previously associated
with the regulation of epigenetics in T Cells. Loss of TOX3 prior to RL specification leads to almost complete
agenesis of CGCs and 100% penetrant ataxia. We hypothesize that TOX3 mediates an epigenetic switch
necessary for the generation of cerebellar granule cell precursors from the rhombic lip and associated
ventricular zone—the loss of which results in developmental ataxia. Using our mature bioinformatics
pipelines and single-cell approaches in combination with both mouse and human models systems, we will
propose to investigate the mechanisms by which Tox3 regulates cerebellar histogenesis.
We propose to carry out this work in two parts. The focus of Specific Aim 1 is to interrogate the epigenetic
and transcriptomic consequences of cKO of Tox3 using multimodal single-cell RNA- and ATAC-sequencing
combined with single-cell Cut&Tag to determine genetic networks regulating VZ/RL precursors and CGC
genesis. The main goal of Specific Aim 2 is to define the role of TOX3 on murine cerebellar lineages using
inducible Cre drivers and somatic mutagenesis.

## Key facts

- **NIH application ID:** 10799992
- **Project number:** 1R56NS131782-01
- **Recipient organization:** CEDARS-SINAI MEDICAL CENTER
- **Principal Investigator:** Joshua John Breunig
- **Activity code:** R56 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2023
- **Award amount:** $584,500
- **Award type:** 1
- **Project period:** 2023-04-15 → 2024-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10799992

## Citation

> US National Institutes of Health, RePORTER application 10799992, Defining the role of Tox3 in congenital cerebellar hypoplasia and ataxia (1R56NS131782-01). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10799992. Licensed CC0.

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