An efficient rAAV vector for protein expression in cortical parvalbumin expressing interneurons

Area of Science:

• Neuroscience
• Molecular Biology
• Gene Therapy

Background:

• Recombinant adeno-associated viruses (rAAV) are crucial tools in research and clinical gene therapy.
• A need exists for short, specific promoters to drive gene expression in targeted neuronal populations, particularly cortical interneurons.

Purpose of the Study:

• To design and validate a novel rAAV vector for efficient and specific gene expression in cortical interneurons, with a focus on parvalbumin-expressing cells.
• To create a short promoter suitable for rAAV vectors targeting specific neuronal subtypes.

Main Methods:

• A short parvalbumin promoter and a specialized poly(A) sequence were engineered into an rAAV vector, utilizing conserved non-coding regions of the parvalbumin gene.
• rAAV particles were stereotactically injected into the visual cortex (V1/V2) of adult rats.
• Expression specificity was assessed via co-localization of eGFP reporter gene expression with neuronal markers (parvalbumin, somatostatin, VIP, CCK, CaMKII).
• Functional efficiency was confirmed using optogenetics by expressing channelrhodopsin-2 (ChR2) and measuring neuronal firing responses.

Main Results:

• Injected rAAV vectors resulted in eGFP expression predominantly in interneurons, with high specificity for parvalbumin-positive cells (66.5%).
• Expression was also observed in somatostatin (14.6%), VIP (7.1%), and CCK (2.8%) interneurons, with minimal expression in principal cells (CaMKII, 2.1%).
• Optogenetic experiments demonstrated that the expressed ChR2 enabled high-frequency action potential firing in targeted neurons upon light stimulation.

Conclusions:

• The developed rAAV vector, featuring a novel short parvalbumin promoter, enables highly specific gene expression in cortical interneurons.
• This vector shows a strong preference for parvalbumin-positive interneurons, offering a valuable tool for studying these neuronal populations.
• The findings support the utility of this vector for targeted gene delivery and functional manipulation in neuroscience research.