Adeno-Associated Virus (AAV) for Tracking Neural Development and Connectivity in Xenopus.

Adeno-associated viruses (AAVs) provide a versatile tool for labeling neurons in the Xenopus central nervous system across developmental stages. AAV-mediated transgene expression is long-lasting and stable, enabling robust labeling of neuronal populations without genomic integration and without the need to generate transgenic lines. The choice of AAV capsid and promoter can restrict expression to a population of interest, and depending on the route and timing of delivery, AAVs can selectively target either progenitor-derived neuronal cohorts or mature neuronal populations. Here, we have outlined two labeling strategies. First, intraventricular injections in tadpoles transduce neural progenitor cells lining the ventricular system, resulting in cohort-based labeling of neurons as they differentiate during development. Second, direct intraparenchymal injections in post-metamorphic frogs enable spatially restricted labeling and anterograde or retrograde tracing of connectivity within defined brain regions. Together, these approaches provide selective access to developing and mature neural circuits in X. laevis, supporting applications ranging from anatomical tracing to functional imaging and manipulation of neural circuits.