Adeno-associated viruses for efficient gene expression in the axolotl nervous system

PNAS, 2025 · DOI: https://doi.org/10.1073/pnas.2421373122 · Published: March 5, 2025

Regenerative Medicine Neurology Genetics

Simple Explanation

This study introduces viral transduction techniques for the axolotl nervous system. It characterizes Adeno-associated viruses for successful gene delivery, enabling projection mapping in the axolotl brain, spinal cord, and retina. The researchers demonstrate the use of AAVs for efficient gene transfer within the axolotl brain, spinal cord, and the retina, showing that serotypes AAV8, AAV9, and AAVPHP.eB are suitable viral vectors to infect both excitatory and inhibitory neuronal populations. AAV9 can trace retrograde and anterograde projections between the retina and the brain, and identify a cell population projecting from the brain to the retina, establishing AAVs as a powerful tool to interrogate neuronal organization in the axolotl.

Study Duration

4 Weeks

Participants

Axolotls (3cm, 5cm, 10cm nose to tail)

Evidence Level

Not specified

Key Findings

1
AAV8, AAV9, and AAVPHP.eB are efficient viral vectors for gene transfer in the axolotl brain and spinal cord.
2
AAVPHP.eB induces a strong immune response in the axolotl brain compared to AAV8 and AAV9.
3
AAV9 is highly efficient for transducing retinal cells and tracing retinal input into the brain, revealing retinopetal projections from the hypothalamus and prethalamus.

Research Summary

This study investigated the functionality and efficiency of AAVs to transduce cells in the axolotl brain, spinal cord, and retina, finding that AAV8, AAV9, and AAVPHP.eB are the most efficient viral vectors for the brain. AAV8, AAV9, and AAVPHP.eB are suited to transduce cells of the spinal cord, including motor neurons (AAV9 and AAVPHP.eB), but AAVPHP.eB showed an increased immune cell infiltration of the injected brains. AAV9 can label input and output projections of the retina through anterograde and retrograde tracing, leading to the detection of a cell population that projects from the brain to the retina.

Practical Implications

Advancing Axolotl Research

The successful implementation of AAV-mediated gene delivery opens up new avenues for studying neural circuit regeneration and function in axolotls.

Understanding Neural Circuits

The ability to trace neuronal projections with AAV9 provides a powerful tool for mapping and manipulating neural circuits in the axolotl brain.

Therapeutic Potential

The findings could potentially inform the development of gene therapies for neurological disorders, leveraging the regenerative capabilities of axolotls.

Study Limitations

1
The study identifies an immune response associated with AAVPHP.eB, suggesting a need for careful consideration when selecting viral vectors.
2
The hSyn and CamKIIa promoters were found to be ineffective in the axolotl system, limiting the ability to target specific cell types.
3
The study focuses on short-term expression (up to 2 months), and further research is needed to assess long-term stability of gene expression.

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