Expression of nACh receptor β4 subunit protein has been detected in non-neuronal cells within the brain (Gahring et al., 2004). In order to determine if the β4 promoter activity we observed throughout the brain is or is not neuron-specific, triple immunofluorescence was carried out using anti-GFAP to label glial cells, anti-NeuN to label neurons and anti-β-gal to label β-gal-expressing cells. As shown in Figure 7, in each region tested, β-gal labeling over-lapped that of NeuN but not GFAP, indicating that the transgene β4 promoter activity is neuron-specific. This suggests that other regulatory elements are involved in the non-neuronal expression of the β4 subunit described by Gahring et al. (2004). Alternatively, post-transcriptional or epigenetic regulatory mechanisms may be at work in non-neuronal cells.
