The success of conditional knockout was determined by PCR analysis of DNA extracted from brain tissue where the virus was injected. Genotyping was performed according to the protocol as previously specified (45 (link)). The following primers were used as indicated in Fig. 1B: P1 F: GCC TAG ATT CAC CTG GCT TC; R: GCT CTT AAC CAT TGA GCC ATC T; P1 KO F: CTT GAC CTG TCC CCT TCC CCA TCA AG; R: AGG TTG CAG GGT GGC ATG GCT CTT TTT and Phire II polymerase (Thermo-Scientific #F-170S). PCR was run following the cycling conditions: initial denaturation: 98 °C for 5 min, followed by 98 °C for 5 s, then 10 cycles of 65°C (−0.5°C/cycle) for 5 s, 68°C for 20 s, followed by 30 cycles of 98 °C for 5 s, 60 °C for 5 s, 72 °C for 20 s, followed by a final hold of 72 °C for 1 min. Reactions were separated on 2% agarose gels, yielding the following band sizes: WT, 188 bp; P1, 380 bp; and P1KO, 230 bp.