A comparison of transduction efficiency of medial septal neurons by adeno-associated viruses with three promoters

Background

Most researchers rely on popular promoters like the synthetic CAG promoter or human synapsin promoter to transduce various brain neurons. However, their effectiveness in transducing forebrain cholinergic neurons remains unclear.

New method

We compared efficacy of transduction of cholinergic neurons and parvalbumin-positive neurons in the medial septal area of rats and mice by adeno-associated viruses (AAVs) carrying the green fluorescent protein (GFP) marker gene under three distinct promoters—CAG, synapsin, and the mouse choline acetyltransferase (CHAT) promoter.

Results

In mice and rats, the CAG and synapsin promoters demonstrated extremely low efficacy for GFP expression in CHAT+ neurons but were effective for transducing PV+ neurons. The CHAT promoter yielded moderate GFP expression in cholinergic neurons in mice, with negligible expression in PV+ neurons, though it also led to off-target expression in other cell types. In rats, the CHAT promoter produced moderate GFP expression in both cholinergic and PV+ neurons; however, the majority of GFP-expressing cells were unrelated to these specific neuronal subtypes.

Comparison with existing methods: Contrary to expectations, human synapsin and CAG promoters provided negligible expression in cholinergic septal neurons in both rats and mice.

Conclusions

The mouse CHAT promoter is significantly more effective for cholinergic neuron expression in rats and mice compared to universal neuronal promoters like CAG and synapsin promoter.