Longitudinal in vivo imaging of adult Danionella cerebrum using standard confocal microscopy

Danionella cerebrum is a new vertebrate model that offers an exciting opportunity to visualize dynamic biological processes in intact adult animals. Key advantages of this model include its small size, life-long optical transparency, genetic amenability and short generation time. Establishing a reliable method for longitudinal in vivo imaging of adult D. cerebrum while maintaining viability will allow in-depth image-based studies of various processes involved in development, disease onset and progression, wound healing, and aging in an intact live animal. Here, a method for both prolonged and longitudinal confocal live imaging of adult D. cerebrum using custom-designed and 3D-printed imaging chambers is described. Two transgenic D. cerebrum lines were created to test the imaging system, i.e. Tg(mpeg1:dendra2) and Tg(kdrl:mCherry-caax). The first line was used to visualize macrophages and microglia, and the second for spatial registration. By using this approach, differences in immune cell morphology and behavior during homeostasis as well as in response to a stab wound or two-photon-induced brain injury were observed in intact adult fish over the course of several days.