Optimization of adeno-associated viral vector-mediated transduction of the corticospinal tract
Adeno-associated viral vectors are widely used as vehicles for gene transfer to the nervous system. The promoter and viral vector serotype are two key factors that determine the expression dynamics of the transgene. In this paper, researchers report a side-by-side comparison between four commonly used promoters: the short CMV early enhancer/chicken β actin (sCAG), human cytomegalovirus (hCMV), mouse phosphoglycerate kinase (mPGK) and human synapsin (hSYN) promoter. This comparison study contributes to improve transgene delivery into the brain and spinal cord. The optimized transduction of the corticospinal tract will be beneficial for spinal cord injury research.
It is important for any gene therapy that transgenes are delivered with high cell specificity and at adequate expression levels. This study investigated the activity of four promoters in a side-by-side comparison in mice and rats at 6 weeks after AAV injection. The AAV1 serotype exhibited neuronal tropism with all four investigated promoters. Yet, the choice of promoter influences: (1) the strength of transgene expression; and (2) the type of cells that will express the transgene of interest.
AAV-mediated gene transfer for spinal cord injury research will require robust expression of regeneration-associated genes in neurons of the CST. The mPGK promoter and hSYN promoters resulted in strong transgene expression, while the commonly used hCMV and sCAG had relatively weak expression in cortical neurons. High cell specificity for layer V corticospinal neurons is crucial to avoid unwanted side effects when delivering regeneration-associated genes.
A promoter with robust and exclusive expression in layer V corticospinal neurons is desired for spinal cord injury experiments; however, to date, such a promoter has not yet been identified. In this study, it was showed that the hSYN promoter has strong transgene expression and is specific to neurons with no expression in glia cells. Based on the data presented here, the AAV1 viral vector serotype and the hSYN promoter is the optimal combination for transgene delivery to the CST of mice and rats.
You can read the full study here.
This research was funded by a Nathalie Rose Barr award (NRB110) from Spinal Research, and supported by a number of international colleagues.