The pseudorabies virus immediate-early promoter directs neuronal tissue-specific expression in transgenic mice

Pseudorabies virus (PRV) immediate-early (IE) gene product is required for expression of the viral early and late genes as a transactivator. The IE gene is expressed as the first gene among the viral genes after the infection. To examine the activity of the IE promoter in vivo, we have generated transgenic mice expressing transgenes under the control of the IE promoter. To analyze the tissue specificity of the transgene expression, mRNA of the transgene was monitored in various tissues from the transgenic mice by reverse transcriptase (RT)-polymerase chain reaction (PCR) analysis. A strong transgene expression was observed in the neuronal tissues by the RT-PCR analysis. These neuronal tissues included cerebrum, cerebellum and trigeminal nerve. Although the PCR product was hardly detected in other tissues by the RT-PCR analysis, specific PCR bands were detected in multiple organs (skin, skeletal muscles, heart muscles, lung, liver, spleen, small intestine and kidney) by Southern blot analysis using the RT-PCR products. These results indicate that although the IE promoter acts as a pan-specific promoter in vivo, it is capable of driving a high level of transgene expression in neuronal tissues.