Nanobody-split Cre Fusion and AAV Purification

For nanobody-split Cre construction, GBP1 and GBP6 (Addgene #50791 and #50796, Tang et al., 2013 (link)) were fused with NCre and CCre from split Cre (gifts from Hirrlinger et al., 2009 (link)). AAV purification was performed as described previously (Zolotukhin et al., 1999 (link)). Since AAV serotypes can show tropism for specific cell types, we used a cocktail of 4 serotypes (2/1, 2/5, 2/8, 2/9). After iodixanol step gradient, the virus solution was dialyzed and concentrated with Amicon Ultra 100k Da filters (EMD Millipore, Billerica, MA) with lactated Ringer. Virus copy number was quantified with real-time PCR. Virus titers were in the range of 10^12-14 gene counts/ml.