Optimization of adeno-associated viral vector-mediated transduction of the corticospinal tract: comparison of four promoters

Gene Therapy, 2021 · DOI: 10.1038/s41434-020-0169-1 · Published: June 23, 2020

Simple Explanation

This study compares four different promoters (sCAG, hCMV, mPGK, and hSYN) to see which one works best for delivering genes into specific brain cells using a virus called AAV1. The goal is to find a promoter that can strongly and selectively turn on genes in cortical neurons, especially those that control movement (corticospinal neurons). The hSYN promoter was particularly good at targeting neurons, while mPGK also showed strong performance. This information can help improve gene therapy for spinal cord injuries.

Study Duration

6 weeks

Participants

20 adult female rats and 20 adult female mice

Evidence Level

Not specified

Key Findings

1
The mPGK and hSYN promoters activated transgenes in significantly more neurons than the sCAG and hCMV promoters.
2
mPGK and hSYN directed higher levels of transgene expression in neurons than the sCAG and hCMV promoters
3
The hSYN promoter mediated neuron-specific transgene expression, whereas the sCAG, hCMV and mPGK promoters directed transgene expression in both neurons and non-neuronal cells.

Research Summary

This study aimed to identify the optimal promoter for strong and neuron-specific transgene expression in cortical neurons, particularly layer V corticospinal neurons, using AAV1 vectors. The hSYN promoter demonstrated neuron-specific expression, activating transgenes in various cortical neuron subpopulations, including layer V pyramidal neurons and PNN-expressing neurons. The mPGK promoter in AAV1 directed strong neuronal expression and limited transgene expression in oligodendrocytes, outperforming hCMV and sCAG promoters in terms of transgene expression.

Practical Implications

Improved Gene Therapy Design

The findings contribute to the optimization of AAV-mediated gene transfer to the CST and cortex, benefiting spinal cord injury research.

Targeted Transgene Expression

The hSYN promoter is identified as the optimal choice for driving transgene expression in corticospinal neurons due to its small size, strength, and neuron specificity.

Cell-Specific Strategies

The study highlights the importance of promoter selection for achieving high cell specificity and adequate expression levels in gene therapy applications.

Study Limitations

1
The ImageJ macro has some limitations, such as requiring the user to set an arbitrary eGFP-to-background intensity ratio to determine whether a cell is eGFP positive.
2
The ImageJ macro is also limited to the detection of round structures only
3
Investigation of expression levels at an earlier time point and potential epigenetic silencing could shed some light on this.

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