FIGURE 1.

Cre-mediated deletion of Cx43 expression. (A) Represents the concept of cre-mediated deletion of floxed DNA at the Cx43 locus, leading to expression of lacZ in the cells that display Cx43 gene activity. Since cre transgene is under the human GFAP promoter (hGFAP-cre), Cx43 is specifically deleted in astrocytes. Cx43 cdr: Cx43 coding region; tk/neo: herpes simplex virus thymidine-kinase/neomycin phosphotransferase; NLS lacZ: lacZ reporter gene with nuclear localization signal; SV40 pA: SV40 polyadenylation signal; H: HindIII restriction site [Adapted from Theis et al. (2003)]. (B) Represents experimental strategy of microinjecting HIV-infected/uninfected human U87-CD4-CCR5 cells in Cx43^fl/fl and hGFAP-cre Cx43^fl/fl mice. Human U87-CD4-CCR5 astrocytoma cells were infected with HIV_ADA (50 ng/ml) for 24 h, and then microinjected into cortices of Cx43^fl/fl and hGFAP-cre Cx43^fl/fl mice. After 48 h of microinjection, extent of bystander toxicity was analyzed in the mouse cortex by detecting apoptosis with TUNEL assay. In the contra-lateral hemisphere, mice were injected with uninfected U87-CD4-CCR5 cells, which served as control for microinjection of HIV-infected cells.