Dual-promoter lentiviral vectors for constitutive and regulated gene expression in neurons

Gene transfer methods for efficient co-expression of exogenous proteins in neurons are crucial tools towards the understanding of the molecular basis of the central nervous system. Lentiviruses are retroviral vectors that can transduce a wide variety of cells including differentiated neurons. In this work, we have generated lentiviral vectors containing dual promoters that allow efficient co-expression of exogenous proteins in neurons. We show that insertion of two copies of a human synapsin promoter/WPRE cassette in a single lentiviral vector directs robust co-expression of cDNAs in cultured neurons, while excluding expression in the surrounding glial cells. Furthermore, insertion of the tetracycline-inducible system (Tet-off) controlled by the synapsin promoter results in tightly regulated expression of EGFP when used as a transgene in cultured neurons. Transduction of primary neurons with this inducible system leads to a 100-fold increase in EGFP mRNA levels in the absence of doxycycline. In transduced cultures, EGFP transcription is inhibited within 24 h upon addition of doxycycline. The viral systems we developed here provide neuron-specific and regulated expression mediated by single lentiviral vectors and will prove valuable tools for the study of neuronal function.