However, even though the Syn promoter restricts the cell type to neurons in which the transgene is expressed via the vectors, it is still impossible to avoid infection to non-neuronal cells (i.e., glial cells) with these serotypes per se, and transgene expression due to leaky Syn promoter activity or ITR promoter activity may occur as we observed in the case of AAV1- and AAV9-Syn-mKO1 vector injections into the monkey cortex45. Here, GPR180 is linked to infection.