Schematic representation of this study and virus production in DF-1 cells by RCAS vectors. A Overview of this study. The CRISPR/Cas9 vectors including Cas9 protein-coding sequences, tvb-targeting guide RNA and neomycin resistance genes were transfected into DF-1 cells. After G418 selection, T7E1 assays and TA cloning were performed. tvb-modified single DF-1 cells were cultured in 96-well plates, and tvb from individual DF-1 clones was sequenced. Clones were infected with ALV subgroup B produced by RCASBP-(B)-CN-EGFP vector-transfected DF-1 cells. B ALV subgroup B production in DF-1 cells. DF-1 cells transfected with RCASBP-(B)-CN-EGFP vectors expressed green fluorescent protein (GFP). Non-transfected DF-1 cells (WT) used as negative control. Scale bar = 200 µm.