# Non-Apoptotic Functions of Caspase-3 in Brainstem Development

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA-IRVINE · 2024 · $590,478

## Abstract

ABSTRACT
Auditory function relies on highly specialized and precise neuronal connectivity. A significant
challenge for the field of auditory neuroscience is to understand how these neural circuits form during
development. Our previous work suggests an important function for caspase-3, a protease best
known for its role in apoptosis. Cleaved (active) caspase-3 is present in the developing auditory
brainstem prior to the period of programmed cell death. During embryonic development, it is first
seen in auditory nerve axons, then in the synaptic target of these axons in nucleus magnocellularis
(NM), then in the synaptic target of NM, in nucleus laminaris (NL) dendrites. Caspase-3 inhibition
during development results in substantial errors in NM axon targeting and in structural abnormalities
in NL, with incomplete lamination. We propose to investigate the regulation of caspase-3 activation
during development. We will examine the basis for the progression of caspase-3 activation through
the auditory pathway and test the hypothesis that cleaved caspase-3 is necessary in auditory axons
for activation of caspase-3 in their synaptic targets. Given the extent of anatomical circuit disruption
that occurs when caspase-3 is inhibited, we will investigate the effects of caspase-3 inhibition on
maturation of auditory brainstem synapses. We will test auditory brainstem responses in hatchlings
after caspase-3 inhibition to determine effects on hearing. We have begun to investigate the
molecules through which caspase-3 influences auditory development. Our proteomics study revealed
hundreds of proteins that are cleaved by caspase-3 in the developing auditory brainstem. Gene
ontology analysis revealed that the most abundant cellular localization category for caspase-3
substrates was exosomes/extracellular vesicles (EVs). This finding suggests an overarching model in
which caspase-3 influences the composition of EVs, which in turn provide an effective means of local
communication between cells during development. We will examine enriched EV samples using
tandem mass spectrometry to determine how caspase-3 regulates the protein content of EVs. We will
test whether pharmacological disruption of EV formation impairs auditory development. We will use an
EV grafting strategy to investigate whether EVs can rescue developmental deficits in caspase-3
inhibited host embryos. Together, these studies will advance our understanding of neural circuit
assembly in the developing auditory brainstem.

## Key facts

- **NIH application ID:** 10888087
- **Project number:** 1R01DC021209-01A1
- **Recipient organization:** UNIVERSITY OF CALIFORNIA-IRVINE
- **Principal Investigator:** Karina S Cramer
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $590,478
- **Award type:** 1
- **Project period:** 2024-09-01 → 2029-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10888087

## Citation

> US National Institutes of Health, RePORTER application 10888087, Non-Apoptotic Functions of Caspase-3 in Brainstem Development (1R01DC021209-01A1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10888087. Licensed CC0.

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