TH and infection: The subsequent qRT-PCR analyses confirmed that, unlike the reduced TH mRNA quantities obtained in the distal axons of CRISPR-infected neurons (mean 0.06 ± 0.01 control vs 0.01 ± 0.002 CRISPR relative quantity, p ≤ 0.01; Fig. 2B), nearly equal amounts of the TH transcripts were present in the cell bodies 5 d after CRISPR infection (mean 0.14 ± 0.01 control vs 0.13 ± 0.01 CRISPR relative quantity, p ≤ 0.51; Fig. 2C), indicating that genomic deletion of the zip-code selectively reduces the abundance of axonal TH mRNA.