iBAC-MAPT exhibits correct cell-type specific regulation of tau protein expression. (a) Primary neurons, but not D74 glial cells, strongly express endogenous tau protein by western blot. (b) D74 glia and primary neuronal cultures were transduced with iBAC-MAPT (MOI = 1) after 1 or 5 days in culture, respectively. Vector backbone-encoded GFP expression confirms efficient iBAC-MAPT delivery to both the D74 glial cell line and primary neuronal cultures 24-hours post-transduction. RT-PCR confirms iBAC-MAPT transgene RNA is expressed in both glial and neuronal cells 2-days post-transduction. However, transgenic tau protein measured by enzyme-linked immunosorbent assay is expressed only in transduced neuronal cells, but not in glial cells, an expression pattern matching that observed for endogenous expression.