nox2/cybb Deficiency Affects Zebrafish Retinotectal Connectivity

Area of Science:

• Neuroscience
• Developmental Biology
• Cell Biology

Background:

• NADPH oxidase (Nox) enzymes generate reactive oxygen species (ROS) implicated in neuronal development and function.
• The specific roles of individual Nox isoforms in vivo during nervous system development remain largely unknown.

Purpose of the Study:

• To investigate the role of Nox activity and specific isoforms in the development of retinotectal connections in zebrafish embryos.
• To elucidate the in vivo function of Nox enzymes in axonal guidance and target innervation.

Main Methods:

• Utilized zebrafish embryos as a model system for studying retinotectal development.
• Applied a pan-Nox inhibitor (celastrol) and hydrogen peroxide (H2O2) to assess the effects of global Nox inhibition and ROS availability.
• Generated isoform-specific knockout zebrafish mutants using CRISPR/Cas9 technology to examine the function of individual Nox genes.
• Cultured retinal ganglion cells to assess cell-autonomous effects of Nox inhibition on neurite outgrowth.

Main Results:

• Pan-Nox inhibition led to abnormal retinal development, including ganglion cell layer expansion, optic nerve thinning, and reduced optic tectum innervation.
• Nox2/cybb chimeric and homozygous mutants exhibited optic nerve thinning, decreased optic tectum innervation, and mistargeted retinal axons.
• Nox inhibition reduced neurite outgrowth in cultured retinal ganglion cells, indicating a cell-autonomous role.

Conclusions:

• Nox2/Cybb plays a critical role in the development of retinotectal connections in zebrafish.
• Nox enzymes, particularly Nox2/Cybb, are essential for axonal development and accurate target innervation in the central nervous system in vivo.
• This study highlights the importance of ROS signaling mediated by specific Nox isoforms in establishing neural circuitry.