Matching developmental timelines of fish, frog, mouse and human brains

The overall structure and development of the central nervous system (CNS) are highly conserved among vertebrates. Peak neurogenesis generally precedes the main wave of astrogliogenesis; exuberant synapses are formed and pruned during critical periods; and the neurotransmitter gamma-aminobutyric acid (GABA) shifts from depolarizing to hyperpolarizing as the brain matures. The sequence of these key developmental events is broadly similar across vertebrate model organisms, including mouse, Xenopus, and zebrafish. Despite this overall similarity, the relative duration of each event varies substantially, and key events such as live birth in mammals do not occur in fish or frogs. These differences must be considered when translating findings from one species to another. In this review, we compare several developmental events that are relevant to modeling human diseases in animal models, including microglial colonization and blood-brain barrier formation. We also present comparative developmental timelines as a resource for translational neuroscience research.