Early ultraviolet exposure disrupts late dorsal fin skeletal development in zebrafish

BACKGROUND: Most organisms on earth experience ultraviolet radiation. High levels of ultraviolet B radiation can cause DNA and protein damage. Zebrafish have become a popular model to investigate the impact of ultraviolet B radiation. Previous studies have identified that early ultraviolet B radiation damages the transient, larval fin fold by inducing apoptosis. However, until now it remained unknown how this early exposure affects late-forming skeletal structures. RESULTS: We determined that ultraviolet B radiation at early stages results in skeletal phenotypes appearing weeks later. Specifically, the dorsal fin skeleton fails to form following early larval exposure. Additionally, this early treatment results in disorganization of the late-forming anal fin and vertebral skeletal structures. We found that inbreeding sensitizes fish to this environmental perturbation, resulting in greater penetrance and expressivity of ultraviolet B radiation-induced phenotypes. These skeletal phenotypes were preceded by larval fin fold damage, precluding mesenchymal skeletal progenitor invasion, resulting in disruption of dorsal fin skeletal development. CONCLUSIONS: Ultraviolet B exposure early in zebrafish development variably damages the larval fin fold, resulting in variable loss of the adult dorsal fin skeleton, a structure that develops much later in life.