A novel AAV1 variant for transduction of Japanese quail neurons in vitro and in vivo

Abstract The widespread use of rodents in neuroscience has prompted the development of optimized viral variants for transduction of brain cells, in vivo. However, many of the viruses developed are less efficient in other model organisms, with birds being among the most resistant to infection by current viral tools. Resultantly, the use of genetically-encoded tools and methods in avian species is scarce; markedly holding the field back. We sought to bridge this gap by developing custom viruses towards the transduction of brain cells of the Japanese quail. We first develop a unique protocol for culturing primary neurons and glia from quail embryos, followed by characterization of cultures via immunostaining, single cell mRNA sequencing and patch clamp electrophysiology. We then leverage the cultures for the rapid screening of various viruses, only to find that all yielded very poor to no infection of cells in vitro. However, few infected neurons were obtained by AAV1 and AAV2. Scrutiny of the sequence of the AAV receptor found in quail led us to rationally design novel AAV variants, with one variant (AAV1-T593K; AAV1*) showing improved transduction efficiency in vitro and in vivo. Together, we present a novel culturing method, unique transcriptome profiles of quail’s brain cells and a custom-tailored AAV1 for transduction of quail neurons in vitro and in vivo.