GFAP and infection: Moving to an in vivo experiment, the authors transduced the striatum of a Gfap-Cre transgenic mouse using an adeno-associated virus serotype 2 (AAV2) engineered to encode shRNA against Ptb linked to a loxP-RFP reporter that could be expressed when infection occurs in cells expressing Cre-recombinase under the astrocyte-specific Gfap promoter.