# A Cre‐dependent lentiviral vector for neuron subtype‐specific expression of large proteins

## TL;DR

This paper introduces a new lentiviral vector that allows for specific gene expression in certain types of neurons in the brain, using a Cre-dependent system and a self-cleaving peptide.

## Contribution

The novel contribution is a flexible, Cre-dependent lentiviral vector that enables subtype-specific expression of large genes in neurons.

## Key findings

- The vector successfully targeted gene expression in neocortical interneurons and midbrain dopaminergic neurons.
- Gene expression occurred only in Cre-expressing neurons without affecting their electrophysiological properties.
- The system allows for visual identification of targeted neurons using fluorescence in living brain slices.

## Abstract

Lentiviral vectors are powerful tools for long‐term expression of large genes in the mammalian brain, but the palette of lentiviral tools available for targeting specific cell subpopulations is restricted. We describe a lentiviral vector for neuronal subtype‐specific expression in Cre mouse lines. Combining a Cre‐dependent flip excision switch with a GFP and a 2A self‐cleaving peptide, it enables identification of living neurons expressing a gene of interest using fluorescence. We validated this vector by targeting neocortical interneuron types and midbrain dopaminergic neurons. Gene expression occurred exclusively in Cre‐expressing neurons without altering their basic electrophysiological properties. This system has been designed to be flexible and easy to modify in order to target expression of any gene of interest in any cell subtype.

We designed a versatile and modular lentivector comprising a Cre‐dependent switch and self‐cleaving 2A peptide and tested it for co‐expression of GFP and a 2.8 kb gene of interest (GOI) in mouse cortical parvalbumin (PV+) interneurons and midbrain dopamine (TH+) neurons. The vector enabled visual identification of targeted neurons in living brain slices and did not alter their electrophysiological properties.