Axonal Cleaved Caspase-3 Regulates Axon Targeting and Morphogenesis in the Developing Auditory Brainstem.

Area of Science:

• Neuroscience
• Developmental Biology
• Cell Biology

Background:

• Caspase-3, a cysteine protease, is primarily known for its role in programmed cell death.
• Emerging evidence suggests caspase-3 also participates in cell differentiation, proliferation, and morphology.
• Its specific function in the development of the auditory brainstem remains largely unexplored.

Purpose of the Study:

• To investigate the role of caspase-3 in the embryogenesis of chick auditory brainstem nuclei.
• To elucidate the temporal and spatial expression patterns of caspase-3 during auditory pathway development.
• To determine the functional impact of caspase-3 inhibition on neuronal morphology and axon guidance.

Main Methods:

• Utilized immunofluorescence staining on chick embryos (E6-E13) to map cleaved caspase-3 expression.
• Administered a specific caspase-3 inhibitor (Z-DEVD-FMK) to block caspase-3 activity during critical developmental windows (E6-E9).
• Assessed the morphology of nucleus magnocellularis (NM) and nucleus laminaris (NL), and NM axonal targeting at E10 in treated and control embryos.

Main Results:

• Cleaved caspase-3 expression followed an ascending anatomical pathway within the developing auditory system, starting from the VIIIth nerve and progressing to NM and NL.
• Inhibition of caspase-3 led to disorganized NL lamination and abnormal glial cell infiltration in the surrounding neuropil.
• Blocking caspase-3 activity resulted in misrouted NM axons projecting to incorrect regions within the NL, with severity correlating to NL disorganization.

Conclusions:

• Caspase-3 plays a critical role in the normal development of chick auditory brainstem nuclei.
• The temporal and spatial expression of caspase-3 suggests its involvement in guiding axonal projections and organizing target nuclei.
• Axonal targeting and target nucleus morphogenesis appear to be coordinated processes, potentially mediated by caspase-3 signaling through axon-target interactions.