Characterization of the properties of seven promoters in the motor cortex of rats and monkeys after lentiviral vector-mediated gene transfer.

Lentiviral vectors deliver transgenes efficiently to a wide range of neuronal cell types in the mammalian central nervous system. To drive gene expression, internal promoters are essential; however, the in vivo properties of promoters, such as their cell type specificity and gene expression activity, are not well known, especially in the nonhuman primate brain. Here, the properties of five ubiquitous promoters (murine stem cell virus [MSCV], cytomegalovirus [CMV], CMV early enhancer/chicken β-actin [CAG], human elongation factor-1α [EF-1α], and Rous sarcoma virus [RSV]) and two cell type-specific promoters (rat synapsin I and mouse α-calcium/calmodulin-dependent protein kinase II [CaMKIIα]) in rat and monkey motor cortices in vivo were characterized. Vesicular stomatitis virus G (VSV-G)-pseudotyped lentiviral vectors expressing enhanced green fluorescent protein (EGFP) under the control of the various promoters were prepared and injected into rat and monkey motor cortices. Immunohistochemical analysis revealed that all of the VSV-G-pseudotyped lentiviral vectors had strong endogenous neuronal tropisms in rat and monkey brains. Among the seven promoters, the CMV promoter showed modest expression in glial cells (9.4%) of the rat brain, whereas the five ubiquitous promoters (MSCV, CMV, CAG, EF-1α, and RSV) showed expression in glial cells (7.0-14.7%) in the monkey brain. Cell type-specific synapsin I and CaMKIIα promoters showed excitatory neuron-specific expression in the monkey brain (synapsin I, 99.7%; CaMKIIα, 100.0%), but their specificities for excitatory neurons were significantly lower in the rat brain (synapsin I, 94.6%; CaMKIIα, 93.7%). These findings could be useful in basic and clinical neuroscience research for the design of vectors that efficiently deliver and express transgenes into rat and monkey brains.